Did Liars and Thieves Misdiagnose this Car or Am I the Bad Guy

2007 Jeep Commander with misfire issue that two shops were unable to diagnose, but they had no problem finding just about everything else wrong with the car. So the owner brought it to me to help out.

[@sheerwillsurvival2064]

He’s back !!

[@rplayer9969]

Well Matt, I've left you a few comments before. I'm almost 73 now. I have 2 hobbies, watching your videos and bowling. 25 - 300's. Looks like I'm gonna sign up to your channel. Tell me how to enlist. You are the GREATEST. And yes. I yelled " GREATEST " !!!

[@SchrodingersBox]

Hahah thanks so much. By the way I worked at a bowling alley when I was 15. Was there for 13 years. Never bowled a 300. 279 is my best. I never seen anyone bowl 25 300’s but I remember watching a guy bowl a 898 series.

[@BblastedD]

Matt dropping some red pills in this one. Thieves = admired. Honest = suspicion.

[@rmr5740]

That's how you achieve "equity".

[@mph5896]

Well, compression test you get a very brief blast of air/pressure on the leaky section of the gasket. Leak down test is a consistent pressure being held on a weak gasket.

[@carlm2590]

God bless you for not charging them, and the good video

[@r.weaver3769]

Matt, I agree, when I was working as a tech, my philosophy was always "If you pay more attention to helping the customer than what it pays, your paycheck will take care of itself". My goals were always fixing the car right or leaving it in the same condition it was when it rolled out of the factory.

[@SchrodingersBox]

How funny because I have used a nearly identical version of that with my clients for my real job. “If you take care of your clients, they take care of your numbers”. It’s a great philosophy! Glad to see someone else who owns it too!!

[@charlesgould8436]

I think of the car, not who's driving. I think of drivers driving home:)

[@MrCountmein3]

Yes a honest person with a conscience. Great job. You make Great videos. You have a wealth of knowledge that you share with us. Thank you.

[@SchrodingersBox]

thanks for the nice comment!

[@Eddiegrant69]

If you put a pulse sensor or a pressure transducer connected to your pico into the coolant neck, you might see a small pressure increase when the bad cylinder is on compression. This should work because you had pressure in there after cranking when you took the cap off. If there is a misfire, you can put them in the exhaust aswell. This would be very helpful to pinpoint which cylinder to test if there was no misfire data.

[@SchrodingersBox]

great recommendation!!!

[@John76546-x]

You got here first. This should pick up the pressure pulses going into the cooling system. Might be more accurate with a pulse sensor.

[@bleebleblahble8833]

Please do a follow up if possible. Would be great to see.

[@NZdiagnostics]

Came here to say this too! Sync it with a coil or fuel injector and you can locate the exact problem cylinder. It works with either a regular transducer or a first look type pulse sensor. Super quick, accurate and easy.

[@SEXYTECH1000]

@@NZdiagnostics GREAT ADVICE , BUT ALWAYS SINC TO THE COIL NOT THE INJECTOR , INJECTOR FIRE BEFORE AND AFTER INTAKE VALVE OPENS AND CLOSES SO IT'S NOT TRUE TDC. THE COIL TIMING WILL BE MORE ACCURATE.

[@joejones711]

Love how you’re precise and the fact you’re not trying to mess people over. VERY SMART MAN

[@billnelson269]

I've owned a shop for 15 years. You are spot on. We operate with old school morals and ethics. I turn away roughly 20 people per day. And my customers won't go anywhere else. Honesty is easy and WILL make the money flow.

[@SchrodingersBox]

Bravo!!!!!!

[@pamelavance648]

Location please

[@SchrodingersBox]

Denver Colorado

[@carguy1312]

Rest assured you didn’t steel the customer, the other shops all but forced them to you. You’re such an inspiration to all of us. Thank you for talking through the thought process of being a good human.

[@SchrodingersBox]

Good way of looking at it!!

[@wheelersgarage8393]

Matt. The reason the compression test lied is the water can not get out of the way fast enough. Cheers Adam

[@SchrodingersBox]

Oooohhhhh!!! that’s a good thought!!

[@brownwrench]

Not blown out big enough

[@wheelersgarage8393]

Yes true and is a factor. Water can't be compressed. If there was no water in the system, you should see a difference in the maximum compression reached. The difference may only be very slight, depending on the size of the blow out though.

[@smiles7631]

I have worked at a couple shops over the years and it doesn't suprise me that they look over the whole car. I remember the franchise would make us fill out these forms for every car that came in. I would feel sorry for the customer that just wanted an oil change and got a qoute for 1000 worth of work. Anyways, I just do this to help people out and make a little extra money now. I love watching these videos and learning about all the new tools that come out. I just bought an inspection camera from the big A for 100 and I was floored by how clear the video is and it has a side view camera. I would bet that if you pulled the spark plugs and looked in the cylinder with this camera you could see the staem cleaned piston right away. Thank you for the video!

[@SchrodingersBox]

Great comment. Yes it is hilarious to me when I see these write ups for thousands of dollars when the customer wants new tires or whatever. Sheeesh lol. Yeah I totally which I borescoped the cylinder. Also the presence of enough coolant in the cylinder probably made it so it couldn’t be squeezed out and thus the compression didn’t lower.

[@r.weaver3769]

I too have worked at shops that require those forms. One shop owner said, "If theres iron on the rack theres money to be made" Didn't take long to leave that one.

[@charlesgould8436]

When I bring my vehicle to someone for diagnosis it is nice to know everything!:)))

[@mikebaz7843]

Sometimes you can't win. If you quote roadworthy items to prevent "since you worked on my car.." they don't like it, but if you don't quote oil leaks and bald tyres, they get upset too

[@williamburdon6993]

I think you did a great job, and I hope this person becomes a great customer for you in the future. I feel like you do, treat people honestly, you will sleep much better at night. My wife gets so angry with me because at 73 with a bad back and shoulders I do everything myself, I told her "I would love to pay someone competent a great wage to fix things for me , but every time I do that, they do not do the job correctly, or they skip steps for a few dollars and it looks crappy or only lasts a short time.

[@JohnDoesGarage]

We are both on the same soapbox. I would love to go fishing with you so we could commiserate on just how despicably pathetic society has become. If I have learned anything in my over forty years of spinning wrenches, it is there are no absolutes in this profession. You will eventually run across a vehicle that will make a liar out of you. It's just part of the gig. Great video as usual.

[@SchrodingersBox]

Thanks my friend. If you ever find yourself in Denver let me know!! Lots of fishing here!!

[@JohnDoesGarage]

@@SchrodingersBox I’ll certainly do it.

[@edwardturello2782]

Awesome video Matt, glad you're back. I always thought that a cylinder pressure test was the answer for compression problems but I stand corrected so thanks again for PROVING it on video and pointing out a better way to diagnose that type of problem. I don't mind putting in the work if the results are correct and by the way I share your views on the current declining status of our American values

[@SchrodingersBox]

So glad to hear - on all counts!!! Yeah I don’t mind admitting I am wrong and my reliance on compression tests earlier on was indeed an oversight. It can be misleading.

[@ourkid2000]

Great video Matt! Flat rate master did a pretty cool video about head gasket testing and he mentioned an interesting method of pressurizing the cooling system and looking in the cylinder with one of those endoscopes for the appearance of wetness on top of the pistons......thought that was a pretty neat idea.

[@northernpatriot9078]

Hey thank you sir I bought xtool it helped me fix a friend's misfire and transfer case encoder motor fix thank you sir 😊!! Fuel trims look 👍

[@SchrodingersBox]

great to hear!!!

[@chriscooper2454]

BTW, you're the greatest chemist/engineer/mechanic I've seen, hands down

[@SchrodingersBox]

much appreciated lol!

[@Leesherwood]

Knowledge is Power

[@Netherlands031]

About the test 'lying' - seems to me that if you have a small leak, then that won't show up on the compression test but it can be big enough to let coolant into the cylinder and cause problems there. You only need a few drops of coolant every engine rotation for a big problem, but a few drops of air missing from the compression, you won't notice. Also, applying a denoising (lowpass) filter to the starter waveforms might help a lot, they're so fuzzy now you can't see much.

[@robertmedina6875]

You are very sharp!! I am retired …. and I have work every day in a shop diag. cars. It looked like a small leak in the wave form Big Matt! Great video!!!!

[@remodz6385]

You can’t excuse the shop so easily! All they had to do was what MOST people do when they suspect a BHG, a chemical test. It was obvious

[@mustangguy8981]

Compression? Or chemical.

[@mustangguy8981]

I ask honestly cause Idk. But I haven't finished the video either 😬

[@mustangguy8981]

Oh dear Lord... Never mind. I thought there was some kind of advanced type of chem test. This is very common stuff. My bad. I'd have just done a pressure test to begin with a kit.

[@mustangguy8981]

Wow, 27 min in. You humored your buddy, proven that a compression test can't always be counted on over a simple code, and so far, shown the most efficient way of where the coolant is really going. Nice man. Do I have your consent for a brain transplant?? Lol

[@mustangguy8981]

I've finished. Thx for the video.

[@rolandorosales5530]

Hey Matt! What I’ve done in the past is install a coolant pressure tester (cold engine) and leave it (with no pressure) while I crank the engine over just like a relative compression test and if it creates pressure it pretty much guarantees a bad head gasket

[@SchrodingersBox]

Yes I have heard of that too!!

[@rolandorosales5530]

@@SchrodingersBox another thing that I have learned from Eric O. (South Main Auto) and super Mario diagnostics is to install a pulse sensor like the first look in the cooling system and sync it with the relative compression test and and ignition event. You are going to see small bumps on the cylinder/s that may have the leak instead of doing a leak down test on all the cylinders. Personally I have only seen a couple of times since I learned about the test.

[@rolandorosales5530]

Didn’t realize you were making a video about this very test 😅

[@SchrodingersBox]

Hahahaha yes I just did it. Video coming out soon!!

[@spinmyhead1667]

Ima find it hard to believe 2 shops couldnt diagnose that.Could be a case of a customer concealing information.Indeed you said it yourself,now your armed with the knowledge and expertise you have become the bad guy,as you have inferred the 2 previous shops as being.

[@LitoVeloria]

The words "Never" and "Always" are 2 of the most abused words in our vocabulary so I'm very careful in the ways I use them. Compression tests never lie. Faulty equipment and/or misuse usually lie. Engine Compression isn't always affected by head gasket issues. It all depends on what part of the head gasket is damaged. It could be damaged at one of the coolant ports and have nothing to do with Compression or cylinder head could be cracked on an area of a coolant port that is not adjacent to the combustion chamber. Most components have several different tests. Therfore just because it passes one test doesn't always mean it's a good component. The only way to pinpoint and verify is to do all the necessary tests. Hey, thankyou for sharing your vast array of knowledge with us while saving us a great deal of headaches and money as well as discovering fascination of figuring out how things work. Your intelligence, modesty, and honesty are an inspiration to me and I'm glad you do what you do. I don't believe that money makes the world go round like they say. I think it makes some people dizzy going around in circles being busy.

[@reneneron2971]

Matt, the compression test doesn’t lie…it simply isn’t useful for conclusively diagnosing a bad head gasket. It is a basic test to identify the mechanical condition of an ICE to generate sufficient compression for combustion, nothing more. Coolant leaking into a cylinder (or combustion gases out) can be a trivial amount of loss of air compressed relative to that of the displacement of the engine cylinder…for a 2 liter,4 cylinder engine, 500cc of displacement compressed (on EVERY stroke) relative to what may be a pinhole sized leak in the head gasket. Science. A blow-by (leakdown) test or the chemical test of the coolant, both of which you show, are far better tests for detecting a failed head gasket than using a compression gauge, and are just as fast (or faster). That is the explanation…science. Last, since you are an educated man, a diagnostic test is incapable of lying. The results provided may be misleading or inconclusive, but lying is the intent to deceive (knowing information is false). Lying requires more than just data or information. Data doesn’t lie…people do.

[@SchrodingersBox]

Agreed. I should say it is misleading but you are right- it is reporting the conpression accurately

[@jgeorges3061]

MATT, you rock brother as always by sharing ur approach and information with ur viewers and those days most of they call them professional garages are most of the time part changers I work in dealership and most of the time i see part changers not real technicians and most of the time charges the customers for things they do not need what else can i say this is the real world we living in. cheeeeeers

[@SchrodingersBox]

Thanks my friend!

[@atlantasamedaydelivery1769]

Also, Matt, we appreciate your honesty and skill. The society has propped up theieves and conmen in media and music. We need more men of honor to thwart this trend. Be well Matt

[@SchrodingersBox]

Thank you!!

[@DependableAutoTruck]

Electronics will never in a case like this beat leak down test

[@kerryb2689]

Bernie Thompson has a pressure transducer that he uses a scope to measure the pressure pulses in the coolant, then syncs to #1. That may be way more sophisticated than you want to do, because most do-it-yourselfers can't do it. Small leak, large displacement = little compression loss. I don't understand why when you give it throttle you get more white smoke....more throttle = less vacuum sucking coolant in..... unless it's when you let off the throttle after pressurizing the coolant with more throttle.

[@timothymay8917]

the coolant in the cylinder is displacing air thereby raising the compression

[@SchrodingersBox]

Agreed. That makes the most sense. The coolant can’t leave as fast as it entered so compression isn’t changed.

[@jonwillfixit]

Good work! FYI do the chemical test outside, It will pickup hydrocarbons in a garage & give you a false reading, it’s happened to me

[@InsideOfMyOwnMind]

Here's your explanation for it. Consider the differential geometry of the cylinder as the piston travels vs the geometry of the leak. Pistons are fast. Leaks are comparatively slow.The compression tests in all forms will always lie in this scenario. Normally a compression test is only a valid diagnostic tool when you are looking for a substantial cylinder failure like a burned valve or a broken piston/ring, etc. A blown head gasket or even a cracked head is NOT a mechanical failure in the sense that a comp test is designed for. You did the right thing. Chem test, pressure back flow test and general common sense inspection. A leak down, removing all the dynamics of engine operation from the equation is great.. Even that however does not diff between a failed gasket and a cracked head/block. Some times a wet pressure test from the cooling side and a bore scope will reveal the actual location of the leak. There are KZbin videos that actually let you watch the coolant leaking into the cylinder through the head gasket. Cool shit. All my best to Jose here in my town of residence. And a belated welcome to you kind/smart sir. Now come back in mid/late August and tell us how well you like it here.🤣 We know.🤒

[@SchrodingersBox]

I think you are correct in your assessment of why the test failed.

[@markchidester6239]

IMHO, It may be possible the other shop pointed out the other issues to give the customer an ability to make an informed decision on the investment needed into the vehicle. I would imagine if they didn't know all of this information, they would have asked you to do the head gaskets rather than cut their losses. Excellent video! Your line of thinking is fantastic and i completely agree with the "Bad Guy" outlook. The investment outlook is for people who wish to succeed. Absolutely solid advise! Your a good man Matt!

[@joeblow6786]

No, he has 6 children, he can't afford better equipment. That's the general reality of our modern world.

[@LyallBates-xn4jd]

Hi Matt, full radiator, cap off crank engine and look for the bubbles, no tools needed..

[@SchrodingersBox]

the water pump itself often causes bubbles though. I have tried that many times and it’s inconsistent. also- even if it was a cylinder leak- how would I know WHICH cylinder it is?

[@LyallBates-xn4jd]

@@SchrodingersBox Hi Matt, fair comment, but there's a difference between the more consistent small bubbles of a water pump leak and the surge of an compression leak whether it is from a porous cylinder, cracked head or blown head gasket.The point I was making is that you can use this to get a fair idea of the problem on the side of the road away from home or service centre. As for which cylinder it is you could try leaving the spark plug out of each cylinder in turn and see if there's a reduction in pressure in one or more (adjacent) cylinders.

[@SchrodingersBox]

Well wait-- if you have to remove the spark plug to do that, why not just do a leakdown test to bring with? Also what if the cylinders are under the intake manifold? And also what if the compression loss isn’t to the cooling system- how would that be determined- you wouldn’t know with this test. A method is needed where you can identify all cylinder leaks and identify the affected cylinder without removing spark plugs.

[@randyrobison335]

Thanks for sharing. My guess is that the hydrostatic pressure of the coolant is giving you good compression.

[@ImReelySuqi]

I am a mobile mechanic but I also make and sell jewelry on the side. Also work a part time job. Definitely trying to funnel more money out of my mobile mechanic business though

[@SchrodingersBox]

I imagine the mobile mechanic business will have more potential but one thing I can tell you- ALL financially successful people I know always have multiple sources of income. Whether that’s working multiple jobs, investments, having a side business- whatever. So regardless of where you focus I’d say you are on a better track than most!!

[@charlesgould8436]

Saw a 92 accord, no brakes unless you pump, obviously been filled, no visible leaks. Customer says a cylinder issue. I have had a 93 Sanoma...self bleeding:)

[@zackarymcclain164]

Super Mario diagnostics did a great video showing how the relative compression isn’t the end all be all solution to mechanical health.

[@roundcornerent]

"SAY HELLOO TO DA BAD GUY '' lol .. Sounds like a new Schrodinger's Box merch hat ,shirt, or sticker .

[@SchrodingersBox]

can’t live without at least a hat!!

[@alexlee4573]

Excellent! Thank you Mat! Super Mario has an interesting video named "Don't trust relative compression test".

[@SchrodingersBox]

I will have to watch that!!!

[@juansautodiagnostic6199]

I never use a compression gauge, i rather use a pressure transducer and a pulse sensor. more precises. great diag and great find.

[@SchrodingersBox]

What do you do if the compression is not lost to cooling system though?

[@juansautodiagnostic6199]

@@SchrodingersBox like a head gasket issue with a oil coolant passage. i put a pulse sensor in the crank case like where you fill up the oil and use a sync to figure out the cylinder. run the cylinder sync to a CKP or RC. Had one that had misfire in two cylinder and it was a blown head gasket that was 2 and 3 were compromised saw it in a rc test. leak down test or put smoke in cylinder 2 and saw smoke comer out on cylinder 3.

[@SchrodingersBox]

Makes sense!!

[@waynerogers2706]

Food for thought. When metal is cold, it contracts, when it's hot it expands. A cracked head makes more sense with all your tests than a head gasket does. I haven't finished the video yet, but my mind is screaming cracked head.

[@SchrodingersBox]

Yes but temperature made no difference. I believe it’s because coolant pools in the cylinder and can’t be pushed out as fast as it drew in so compression is the same.

[@reneneron2971]

Short answer: chemical test for presence of combustion gases in coolant. If there are gases detected, engine is faulty. Additional diagnosis is required to determine which cylinder(s) have a problem, and the cause is not limited to a head gasket.

[@SchrodingersBox]

Yes but I have a video that also shows a false negative test on the chemical test. I agree I have never seen a false positive but I have seen false negatives several times.

[@reneneron2971]

@@SchrodingersBox note that head gaskets can leak from the combustion chamber to the coolant side or the reverse (coolant side to the combustion side). So, yes, not conclusive by itself. But, in this case, you also had coolant in the combustion chamber (as seen in the exhaust). That is conclusive.

[@atlantasamedaydelivery1769]

The chemical test is awesome. I have to procure that tool or kit for head gasket diagnostics.

[@SchrodingersBox]

One of my favorites!’

[@atlantasamedaydelivery1769]

Matt sir, if I may ask, do you have a particular company that you prefer to use dye to determine if carbon dioxide is in the coolant.

[@mikemuzzell5167]

Car overheats I’m doing a oil changes right away. Good to see you against sir. I did in fact buy the d7 on your recommendation and I’m super happy with it so far. I’m a heavy truck guy and have my fair share of pick ups to work on. This tool makes a lot of diag possible. D7 for the money is the best.

[@SchrodingersBox]

Great to hear!!!

[@Christdeliverme]

Usually when shops pile on services like that, they are trying to scare off the customer, as they don't want to work on it. If it's a dealership, this is where the car salesmen comes in.

[@SchrodingersBox]

Ohhhhhhhhhhhhh!!!!!! Man that’s a really good point!!!!! Never thought of that!!!!

[@gilberthale7777]

Yeah, I have seen that action also. For some cars it is best for the customer to get another car (Pintos for instance), but no need to do it like that... @@SchrodingersBox

[@pnowicki879]

I left the industry in the late 90's due to 2 different dealer shops regularly asking me to rip people off and 'find something we can sell', I just wouldn't do it. I wonder how many good people just leave and move on. I have also experienced, asking for service as a customer and having shops simply reset the light and clear the codes up to having brake lines cut to sell brakes, unreal. These guys today are just so lazy.

[@SchrodingersBox]

I hear you man. I don't work in the industry but I am fully aware of many of the practices- I see it all the time. Thats why I like doing my own thing.

[@Christdeliverme]

Welcome back homie

[@SchrodingersBox]

Wah da tah my damie!!!

[@johnjonz2472]

That sounds like a no quote. It's like they didn't even really want to fix it

[@advancedleveldiagnostics]

Great job Matt, Thanks! Another way the RC test can "Lie" is with a valve issue, that's why It is better to do an RC test with a pulse sensor in the intake. I don't think it would help you in this case unless you put one in the radiator neck as well.

[@SchrodingersBox]

Agreed! Will do that next time for sure.

[@DylanL69]

Most of the time a blown won't show relative compression being different because it was most likely a coolant leak into the cylinders

[@LifeSavingDefense]

The fanciest tool I have is just a fancy code reader that can test battery and alternators and a few other things, I do have the fluid tester and a test light and a digital multimeter, compression gauge, fuel pressure gauge, vacuum gauge, voltage gauges….. the old school basics. That’s it. Been fixing my own cars 40 yrs ans now my kids. Rarely someone else’s just cuz it’s a hobby for me and my kids keep me busy enough although at one time it was a thought. I think it would help some to have better tools but even as a medic I found people depending too much on fancy tools and forgetting the basics. Our brains are the best computers in the world as we see, hear and feel more than we know but less when we depend on other things. Those other mechanics have to just be thieves cuz head gasket is the first thought after over heat ESPECIALLY if the car has the positive pressure cooling system without a true overflow as the pressure has to go somewhere and head gaskets are the weakest place. Thank you for your knowledge and videos. I watched simply cuz your video randomly popped up on yt and I know you always have good info. It’s too bad she go treated so bad as a head gaskets are relatively cheap to fix unless things are warped.

[@TerryBates-ic8rb]

Hi Matt, I agree with the other guys on using a pressure transducer on the radiator and sinking another channel to cylinder 1 to trace down the contributing cylinder following the firing order.

[@TerryBates-ic8rb]

Then verifying pressure loss at that specific cylinder via leak down test.

[@SchrodingersBox]

100% agreed!!

[@nickayivor8432]

Welcome back, Schrodingers Box Enjoy your weekend Schrodingers Box 👍 SHARP Schrodingers Box From Nick Ayivor from London England UK 🇬🇧 ⏰️ 15:51

[@plowe6751]

40:55 Relative compression waveforms can be deceiving in many ways. Scanner Danner did a case study where the valve timing was off on one bank and all the cylinders on that bank had low compression. The other bank was good. The relative compression waveform looked good at first glance. By chance, the firing order on that engine was 123456, which means that the low-compression cylinders were every other cylinder. If the missing humps are on every other cylinder, you won't be able to detect that the humps are missing unless you sync that waveform with an ignition waveform and count the number of humps in 720 degrees of crankshaft rotation. If you count only 3 humps when there should be 6, then that is how you know, you have 3 missing humps. Of course, this doesn't apply to the vehicle in this video because the engine runs, but I thought it was interesting.

[@SchrodingersBox]

Yes I agree- relative compression can be misleading. It must be used in conjunction with other tests, it shouldn’t be used stand-alone.

[@plowe6751]

@@SchrodingersBox Also, Super Mario Diagnostics KZbin channel did a video where relative compression waveform showed uneven humps due to cylinder wash. The car had diesel in the tank when it shouldn't. After adding oil to the cylinders, the relative compression waveform looked good. The lesson is cylinder wash can skew the relative compression waveform.

[@SchrodingersBox]

Absolutely. I always try to disable fuel when I do compression tests for that exact reason!!

[@DependableAutoTruck]

should have been able to put pressure on cooling system and find water entering cylinder still lots of work would have to remove all spark plugs. i ran into it on my wifes truck 360 dodge would skip every morning for a few seconds had good compression. pulled all plugs and checked one had water in it

[@SchrodingersBox]

Thanks Howard. absolutely would be a valid technique.

[@kdmq]

I am learning horseback riding, and various other farm skills to add to my mechanical engineering background. So incidentally, I happen to be building a second skill set as we speak.

[@SchrodingersBox]

Hey that works!!! They always need ranch hands in the rural area of Colorado!

[@scottfishman6254]

Dealership tech here. Another issue is that the dealers don’t charge diagnostic and everyone is on flat rate. They are literally forcing us to guess. If you’re not going to pay me I’m not going to test stuff. Then the customer declines the job I don’t get paid and he goes somewhere else to get it fixed cheaper than the dealership prices, thoughts???

[@SchrodingersBox]

Yeah I am not from the industry but I totally am aware of what you are saying. I totally agree 100% with any policy where the shop charges at very minimum a flat fee for diagnostic and preferably an hourly fee with minimum of 1hr and then you and shop get paid.

[@charlesgould8436]

Leak down seems to be The Test.

[@SchrodingersBox]

It is by far the most reliable and most informative for sure. However it also the most laborious.

[@Lambros_Stefaneas]

i know it's a bit expensive as a tool, but using a gas analyser, is the easiest way,more accurate, and much faster than the other tests. less than 10 seconds. you stick it in the cooling cap,and done.that we was doing in the previous workshop i was working. and even if you don't own, i am sure its going to be something near by.i will suggest you Matt,to give a try to this technique, and share your thoughts.

[@MrOctNot]

Could it be that compression leaks into coolant system don't show in relative compression waveform because "you can't compress a liquid"? Perhaps it should be standard practice to remove the radiator cap when performing relative compression tests. Perhaps even removal of the oil filler cap and a major vacuum line (e.g. brake booster hose).

[@SchrodingersBox]

I absolutely agree that is the best explanation.

[@robertfoilesjr1337]

Just take the rad cap off and crank. No set up needed. Will dx leak into coolant system at least using engine compression already supplied. Obviously not into intake/exhaust/or block. But quick and most common.

[@matthewbrice737]

Super Mario has a good video on this same issue (failed RC test). He puts pulse sensors in coolant & exhaust, amp clamp around battery, coil trigger for sync.

[@SchrodingersBox]

Thanks for sharing!

[@charlesgould8436]

Since compression is mechanical, it seems a more straightforward test is needed.

[@SchrodingersBox]

I have one!! Wait til next video!!

[@charlesgould8436]

Had a95 land cruiser with straight engine, I think 4.7. Milage??? Runs nice! Wanted tires but dead battery no start etc.. checked and charged good bat. Slowly cranked key like 10xs and start. In the middle of changing tires, it started , but with a couple high power fans hard to hear. Ran for 20min or so, long story short, unhooked neg batt. Terminal and cranked the key to start to shutt off vehicle to finish. I'm guessing starter but all this happened after fussy customer showed up. So I don't know if they were mad and remote started or problem with what's on car. I think a car problem. Anyways, I will probably never see that car again:(

[@apollomedia7210]

A friend of mine was paid temporarily via a prepaid card and someone from company had access and spent $990 of it and he could not do anything. I agree, California hates hardworking middle class.

[@frugalprepper]

As far as Hose building a business. It is possible, but when you start doing more you start paying more. He has got to pay taxes on it before he gets caught, because he want to accept debit cards, and everyone wants to pay that way, and he will get 1099's from his credit card proccessor. If he claims it as income then he has to get a vendors license and start collecting sales tax (a time consuming process in Ohio), before they catch him. Now he has got to do accounting to keep track of all his expenses and billing (more time). Now when he does his income taxes he is going to have probably pay an accountant to do them, I don't but most people will. Then he has to get garage keepers insurance, so if he has an accident driving a customers car he is covered. Then he will have to get general liability insurance if he does mobile work at other businesses. Plus he will want an umbrella policy to cover all those policies. It goes on and on and on....

[@SchrodingersBox]

Totally agree. All the MORE reason he deserves his success and reward and all the more reason people who don’t do all of that are not victims of “misfortune”

[@frugalprepper]

@@SchrodingersBox Yeah, a lot of people don't realize the expense and effort you put into you success. In Ohio, it still a crime to steal though, so at least there is that.

[@SchrodingersBox]

Agreed 100%. It also in my opinion explains the dichotomy between the business owner and the unskilled labor. Who deserves to make the bigger share of the profits? Is it the person who built a business out of their garage working 14 hours a day without not even a day off for 5 years, took out a mortgage loan and a business loan in addition to securing capital from private investors, made arrangements with distributers and manufacturers, got insurance, hired employees, hired legal resources, analyzed the market to position for growth, learn antitrust laws, validate zoning restrictions and reinvest for expansion…. Or is it the guy who puts the products on the shelves?

[@Mark.N]

Back to the soapbox--I'm hoping we see a change in the next couple years...

[@christopherfranklin2262]

Matt use the search option next time. It's located I. The top right corner. It's great at detecting keywords. Thanks for the recommendation on the xtool. It's great

[@kinglangren]

Thanks I own the stool and it’s a little cumbersome at finding the needed pids. I squally just use a generic scan tool and go to the stool only if needed. Thanks

[@waynerogers2706]

Hairline crack in head. When engine is cold, no compression loss. When engine is running, combustion gas gets into coolant and vice versa.

[@SchrodingersBox]

I thought that but engine temp makes no difference. I believe it’s because coolant is pooling in cylinder and can’t be forced out during compression stroke as fast as it draws in so compression is same.

[@vieczurable]

There must be an explanation for this cannot be a miracle. What is expected coolant pressure especially at cracking vs air (gas) pressure applied to faulty cylinder during a test? How about slowly increasing applied pressure to see at what force it starts passing to a coolant system. Not every leak must be of same specs - I assume?

[@SchrodingersBox]

There is explanation coming up in a new video and in fact we will even prove the explanation next week.

[@plowe6751]

I think I heard you say bromophenol blue. However, a Motor Trend article by Scott Tsuneishi says bromothymol blue. I googled the 2 terms and according to the internet, those are 2 different chemicals.

[@SchrodingersBox]

Yes I misspoke. It’s bromothymol. Bromophenol is a chemical I use to stain cells at my regular job and I mixed them up lol.

[@chriscooper2454]

Okay,I for one would go work for you, resulting in possibly doubling the "doing the right and honest thing". Just saying,you could have a person or two doing the work and making even more people happier and satisfied.

[@DaveSender66]

Great video Matt. Being a scientist that you are, why don't you discuss with people the possibility of a cracked cylinder head. It is entirely possible that a cracked head could cause the exact same issue that you're seeing here with this vehicle. I would agree with you that the head gasket is leaking however it is a possibility that the head is also cracked between two valves. I believe you should discuss the importance of having a dye and penetrant test done on the aluminum cylinder head before reassembly. I do appreciate you sharing your knowledge with us

[@brownwrench]

Coolant leak in the intake is not possible on the 4.7.

[@SchrodingersBox]

yes agreed I looked up later and it’s a dry intake.

[@grizz5431]

I watched this video earlier this morning. I appreciate a rave as much as the next guy, but yours bothered me. Every business is in business to make money. As a part time mechanic, you work on your time schedule. Techs in a repair shop work on a schedule usually laid out for them at the beginning of the day. Get it in. Get it out. And then there is the bean counter. Whether that is a hired bookkeeper, the shop owners wife, or the shop owner himself, they usually don't know what it is going to take to complete the job. They just know the bottom line has to look good. No excuses, this was an easy diagnosis that the tech should have made. As you said, you know the shop, and the shop probably knows you. I hope that if the tech that worked on this vehicle watches your video, he doesn't take it personally, and gleans some wisdom from your diagnosis. We don't need techs getting disappointed and quitting to pursue another career. Make no mistake, I have a high regard for you and what you do. But, you don't operate a full time shop. You pick and choose what you want to do. Shops don't have that option. If any shop owner is watching this and reading my comment, with age comes wisdom. I am retired. I worked for a top notch sales and service company. We (and I use the word "we" because the owner made everyone feel as they were a vital part of the company) set the standard for every other company in our field to follow. I recently had this conversation with a young man I kind of mentor. Don't do low quality work for a cheap price. Do high quality work and set your price accordingly and let everyone else try to meet your standards. It won't be long before other shops will begin wondering why their customer are going to you even though you charge more., If there is a positive take-away from this, the tech did his job in finding other underlying problems with the vehicle. Would the customer have gone ahead with the engine repairs only to find that the vehicle needed more work done? The customer probably trailered to within a block of a dealer and traded it in. Wouldn't be funny if it showed up at your garage to diagnose an overheating problem.😅 Sorry for the length of this. I just felt it needed to be said.

[@SchrodingersBox]

I absolutely appreciate and respect your perspective for sure and I do not disagree with it. I work in a fortune 200 corporate environment and believe me I know all about bean counters and the bottom line and hitting metrics. We do indeed have different perspectives. I always see things from a customer's perspective even when I am doing a job for pay- and in fact even at my real job. I have even changed jobs a couple times because of this. Everything you said is true however from the customer perspective, they are not aware of the business model and in fact if they were aware of it, they would probably be less inclined to take their car to a business. When a customer has an engine issue like this, its one of the most stressful things possible because they know a huge expense is coming one way or the other. The customer is taking their car to a professional because they need a professional diagnosis on the problem to make the best financial decision possible. When a misdiagnosis like this happens, the customer is put in an even worse situation than they came in with and can lose thousands more than they already expected and it is unfair that the shop profits from it. I in no way disagree with your description of the model- it is accurate. I am challenging the model.

[@brownwrench]

Just the gasket diagnosis might be good enough without a specific cylinder named. Kinda academic at that point unless you possibly want to do only one head.

[@SchrodingersBox]

Yes I agree. usually once i determine 100% it’s a head gasket failure I stop and call customer

[@plowe6751]

I've seen Scanner Danner use a gas analyzer to sniff the radiator fill hole for HCs to diagnose leaking head gaskets. However, gas analyzers that detect HCs are very expensive. The ones I saw on the internet were at least $2000. However, I've seen carbon monoxide testers that measure in a range suitable for leaking head gasket detection listed at $97. It would make for an interesting video if someone would use the scientific method to determine if a cheap $97 carbon monoxide tester can be used to diagnose leaking head gaskets. (A household smoke detector with carbon monoxide detection would definitely not work because the water vapor alone will set off the alarm.)

[@plowe6751]

I forgot to mention, in order to use carbon monoxide to detect a leaking head gasket, the engine probably has to be running rich or at least at stoichiometry, which means the test would have to be done outdoors with plenty of ventilation. I don't know if a lean-running engine would produce enough carbon monoxide to be detectable at the radiator fill if the engine did have a leaking head gasket.

[@DuaneDonaldson]

Commenting as I am watching. Does this tool show a dead module in the full count of the number of modules or it simply skips over it and not enumerate it like some other scanners do? The reason I bring this up is many folks like to know how many modules are on the car that they will work on so for future videos that you scan with this tool, may I pls ask that you scan the vehicle, get the full count on the first go around, then once repaired to do a post-scan, double check the module count to see if one came back to life based on the repair. Some more expensive scanners have a full count near the top of the screen, dead or alive. An RC Test is only a guide, coolant leaks inward to the cylinder on the intake stroke while compression does not leak into the cooling system strongly on the compression stroke but may leak during the power stroke if actually running, during the test this would be the expansion stroke with no real effect, at least not proven as you did not do a compression test on the radiator which may need a very sensitive tool for the scope, you also did not check for an intake vacuum problem which also needs that sensitive tool. Some head gasket leaks seem to be one way as the blown gasket acts as a one-way flap of broken gasket or something like that, many I have worked on only leak when sitting all night and cooling down and allowing the coolant into the cylinder during the cool down cycle only. Up until 18 minutes, you did not use a sync signal to ID which cylinder in the firing order was the actual low compression positively identified with the RC test, although very slightly. Very likely the oil cap was from this issue but need to know if the owner does regular oil changes and more so do they do a lot of short drives, this will condense water in the crankcase quite easily. To read that spark plug we need to pull 2 plugs to see if this one is washed and the other has black or brown residue as an additional verification. In some cases, the plug will be colored/tinted the same as the coolant. Your second RC test is definitive but imagine the first RC test, where is the compression loss going, its a practically full cooling system, so where is the loss going, it must be minimal, drain the coolant and try it again to see what an installed radiator cap and an installed spark plug with an empty cooling system looks like on the scope. Your scope has the ability to clean up all that red noise, I think with a better/cleaner capture you will see the problem easier, I can see the repeatability on the later tests also. Manual compression gauge, first pulse over 90PSI, no problem with rings, no cylinder washdown based on burning coolant so any other compression leak is small and not noticeable via this method as you have stated. Looks like it is too late to compare spark plugs as the previous shop charged them for work that did absolutely nothing to fix the car, and took away the ability for the next mechanic to see the problem right away, (possibly) BIG SURPRISE. Known good cylinder manual compression also over 90PSI on the first pulse, the ring inspection pulse (if low, do it again as you may have already been on the compression stroke and got cheated out of a full stroke). Cutting their losses can be your honest gain, buy it from them Bro. ON YOUR SIDE HERE, if you saw the original spark plug on #7 and compared it, you would have found the problem ASAP. Possible mistakes, red waveform too noisy, blue waveform too short in height, only reading one spark plug (no help in this case but you didn't think of it up front), not syncing the amp wave to a cylinder ID like #1 on a second channel, I believe with a better scope setup, you also would have found the exact cylinder ASAP. THUMBS UP

[@anonintellect9882]

Was compression test done with rad cap off?? Was compression/ pressure being held in cooling system giving false cylinder pressure reading?

[@SchrodingersBox]

Good question. Rad cap was on.

[@anonintellect9882]

@@SchrodingersBox cooling system could have been buffering/maintaining compression, Whenever overheating reported friend of mine would always check oil, then take of rad cap and turn over motor, if oil was milkshake and rad looked like old faithful no further checks were needed, not exhaustive or conclusive but with those checks no water pumps ect would be fitted. Thanks for posting I’ve learnt a-lot from your channel this novel electronic compression test is just one more simple yet genius tip, its great you do good work and share your skills much appreciated, Cheers.

[@secondwindmusicproductions]

How about a pressure transducer in the radiator cap synced with a pulse from number one cylinder to find which one has the blown gasket?

[@SchrodingersBox]

Exactly what I will do in next video!!

[@DukeBlade-ol6pm]

Science doesn’t lie. Test evidence doesn’t lie. Problem is test error or analysis error. Cylinder leak has five potential paths; adjacent cylinder, exhaust, intake, coolant, or external. Your test showed a cylinder to coolant leak path as well as did the inspection and as did the operator symptom description. The engine run test showed a bidirectional coolant to cylinder leak path evidenced by the white smoke in the exhaust. You were experiencing an office effect where source greatly exceeds drain. Not a fault of the tests you selected. Just a fault of analysis. No more of a “lie” than the air compressor pressure gauge lying when the cylinder leak-down tester connected and in use. No more of a “lie” when voltmeter shows battery voltage when a indicator light bulb connected. Solving a system of equations with multiple variables takes more than one test result value. Measuring gas in the coolant was aggregating, not differentiating when you were looking for evidence differentiating between the cylinders. A damp cylinder can cause a misfire as exemplified by the well-known Ford 4.6L plastic intake coolant leak into cylinder 1 causing an intermittent misfire that also destroys the cylinder 1 ignition coil and the bank 1 catalytic converter. Looking for an easy test? Since either a damp cylinder or a misfire can cause a lower temperature exhaust, use a thermal camera to look for the relatively cooler exhaust port. Diagnostic charge? :- ) Don’t say science lies because science never has, just people. Otherwise good video. So the other shops wasted her money so that not enough money was left to salvage the vehicle. That should be a crime.

[@Tony-rl2fr]

A little classic rock humor. I love it! AC⚡️DC 11:37

[@davidvick2616]

What about doing the relative comp test with the radiator cap off so the pressure has somewhere to go

[@SchrodingersBox]

As shown later in the video it makes no difference.

[@paulbinmo]

Awesomeness!!

[@robertjospeh1097]

Can you use a radiator pressure gauge to check? If it pushes that much coolant it should be easy to measure with a pressure gauge. You would be checking all cylinders at once.

[@SchrodingersBox]

Yes indeed you can use that if there is significant enough coolant pressure. But it can be subjective as coolant pressure increases anyway because of temperature.

[@robertjospeh1097]

If there's not a problem it should not increase past the rated cap pressure though, if your getting exhaust gases it should go right past the rated cap pressure I would think..@@SchrodingersBox

[@Anglosax007]

Hi from the other side of the pond, been in diagnostics since it started, 25yrs, must be mad, But great approach to the car, but one thing I was thinking is, can you not do a RC test off of the battery directly with the Pico ? I don't use a Pico, I tend to use my trusty old fluke/tech31 as it has a lovely bar graph for RC tests and just clips on to the car battery? I'm sure I've seen someone else do something like it in a Pico. Just think it may be more of a delicate indicator if that all makes any sense? On tech31 it shows all cylinders in % from 100 down . Sometimes you just can't find what it is, but boy does it get to you not knowing, I love doing autopsies on anything that's failed just to know why. I started doing that about 10yrs old to mum and dad's black and white TV, I was grounded for weeks. Lol All the best guys

[@tomctutor]

As is the case in most scientific tests, you can prove a fail (a positive result in this case), but not a pass. If the RCT indicates a failing cylinder then your done, but if it does not show up you're back to square one just like Matt had! 👍

[@SchrodingersBox]

Yep very true. It’s always important to know the limitations and also the infallibility of any test. I see more and more that I can get false negatives on RCT but I have never ever seen a false positive.

[@MR.KNOWITALL1982]

Hi Matt, Professional mechanic? Is there such a thing? At what point is one to be considered a professional Auto mechanic? after all you don't need a license like every other trade to become a mechanic! That makes it very easy for ANYONE to become a Professional mechanic/ shop. Over the years I have been lucky enough to have worked alongside these "pro's". They really could take a test like a champion. You know, the test like ASE and the OEM type tests. Some of these Techs could not fix a sandwich. Don't get me wrong they are good to have on paper but in real world not so much. I think Clubber Lang would have called them paper champions:) don't get me wrong, I have known tech's that were super stars in the trade. IIn my opinion you're better off bringing your car to someone that can spend the extra time during a diagnosis (someone like you). These shops don't pay enough to perform Diags on every variable a vehicle may have, nor do they want you to spend the extra time. It's get them in, get them out asap. They also charge double what the guy at his home garage is going to charge. This message should get the blood going in some:) on a side note: We miss your troll videos please do more please:) thanks

[@solsol1624]

Wow never seen a compression test done with a scope, genius. One small point, on the blue voltage trace, would it not be the troughs in the wave indicating the extra load as the voltage drops? Unless you had inverted that channel, of course.

[@SchrodingersBox]

Great observation. Yes I inverted the channel only because i wanted it to better align with the amperage pattern that most people are familiar with.

[@solsol1624]

@@SchrodingersBox I thought that was the reason! Just want to say many thanks for your videos and not only the knowledge but also inspiring us to do better ☺

[@mnrujiska771]

What did i miss, on 25:24 voltage drops but there is no current..

[@SchrodingersBox]

Great observation. It’s because I inverted the voltage to make it line up better with current pattern. I mentioned it while filming but somehow lost it in the edits.

[@CrimeVid]

So where the hell did all the steam from the exhaust come from ? a cracked cylinder ? the scope failing is probably because the hole in the gasket is not a very big one

[@SchrodingersBox]

Yes I am surprised how much steam comes from the exhaust from what seems to be an extremely small leak. After the blue devil it didn’t do that anymore.

[@mph5896]

I used to do a TON of those engines. I thought they were decent engines until you overheated them. 😉

[@MarcBchannel]

I had one in a jeep that had cooling issues before I bought it. I fixed the cooling issue but within a year it developed a head gasket leak. I fixed the head gasket and it ran great til I sold it. Very smooth engine. I probably wouldn't buy another one tho☹️

[@mph5896]

Good idea they cut their losses on that car. To fix it properly, 2 new or reman heads to prevent further problems. The 4.7l can drop valve seats when they are overheated.

[@mph5896]

@@MarcBchannel I would buy broken ones cheap 7-10 years ago and fix them. They would drop valve seats, and I have seen a few with bad head gaskets/warped heads. They are decent engines if you change the oil regularly and don't overheat them.

[@MarcBchannel]

Ya I really liked mine. I know of all the issues they had but maintenance is key with anything. Especially on newer vehicles with turbos, vvt, direct injection. I'm a sucker for lost causes. I buy the cars people say suck, tinker with them, and keep em on the road a little longer 😁

[@michael.sierra]

Got a free Ram 1500 with a 4.7. Heater core had failed and the coolant went bye-bye. It had overheated and white smoke was billowing out of the exhaust. Bypassed the heater core, put in some coolant and some Bars HG-1 head gasket fix magic goo, and it was good to go. Decent MPG for what it was, not a bad truck. Sold it for $900. Last I heard the new owner has crashed it twice but it still runs fine. I don't hate the 4.7! Just definitely sensitive to overheating.

[@frugalprepper]

I am wondering, if you don't see it on a relative compression test, because they pressure it leaking into the coolant system where the pressure cant escape. I would try taking the radiator cap off and see if it changes at all.

[@SchrodingersBox]

Totally agree. 100%. Or even drain the coolant. Or a pressure transducer on the radiator. But either way I absolutely agree that’s what caused the compression to be the same.

[@mikesabin8568]

I am going with option C… Liars and thieves misdiagnosed it and matts a bad guy

[@SchrodingersBox]

hahahah dang you are right- I did create a false dilemma didn’t I!!

[@peacepoet1947]

I would have checked compression.

[@peacepoet1947]

The time line is 6:38. So I'm just playing a hunch on the problem.

[@peacepoet1947]

​@@SchrodingersBox you might have removed the hold down bolt on the battery to give you more room to work with when using the meter.

[@peacepoet1947]

​@@SchrodingersBox brown oil is a sign of a cracked block.

[@barryguitarman]

No sparkplug in cyl 7 showed no compression with rc test

[@davyarthurs]

At 08:05 when searching for misfire counters, I notified there is a magnifying glass icon top right, would hitting that give you a search box so you can search for the required data pid? Nice to see you back Matt

[@SchrodingersBox]

Hahaha yes it would have. To be honest I was just showing off how many parameters you get on that tool for the video lol. Actually the misfires are located under active tests anyway where you can turn injectors on and off to do a drop test.

[@davyarthurs]

@@SchrodingersBox 🤣 that’ll teach me for speaking up 😝. Handy features! Even better when you can do these extras without even moving from the driver’s seat😁