Compression/Leak Down test DONT MAKE THIS MISTAKE!

[@CMAutohaus]

Make sure to set the tool gauge back to zero when doing the test!! My Mistake!

[@LTVoyager]

That was only one of your mistakes.

[@nodnarbz_1327]

@@LTVoyager if you’re gonna call him out, say what the mistakes were! You already took the time to comment

[@michaelyount3176]

I make a positive stop out of an old spark plug. Length is set so that when the cylinder you're testing is at TDC, 2 of the other cylinders are at BDC. So, if I'm testing #1 at TDC I screw the stop into cylinder #2 or 3. This locks the engine into place. I don't have to worry about wrestling a wrench to hold it in place. And I can check for noise/leak presence by myself. Also, I close up the garage and turn anything off that makes noise - so I can hear where the leak is coming from. I usually pull the dipstick and stick a piece of tubing in it. Easy to listen to the exposed end of the tube for crankcase noise. Easier to listen to throttle opening on leak down if you pull your screw driver and leave it closed - you'll get more audible noise if you have a leaky intake valve.

[@bigstuff52]

I've been doing automobiles for 48 years..I never thought about rotating the engine till it gets hard to turn...great vid..Pleasure subscribing to your channel...

[@CMAutohaus]

Hey! Glad you found this video useful. I am thank for the the people who have taught me my trade and I am happy to share my knowledge

[@RoRo20699]

Only way I've ever done it. Never made sense to me to hunt for tdc.

[@troyc333]

And don't forget the shop dog. Very important to have the little boss running around making sure the work area is safe.

[@CMAutohaus]

100% agree!

[@alanlaing673]

Need to set the regulator before plug in to cylinder, set the psi in and then turn till it goes as close to zero (set) as possible then lock the regulator, then you can plug in to adapter in the cylinder , you put in 100 psi and it shows up 70 or moderate on the second gauge, you have a 30% leak so to speak ,also each cylinder tested should be at tdc before adding air as the engine could spin and if you have a bar on the crank well good luck ,. Also listen for noise if it’s out the exhaust or the intake air pipe then it’s the valves, if it’s out the coolant it’s your gasket and if it’s out the oil filler then it’s either the block , the liner, the piston or the rings . that’s how I was taught and works for me

[@veehaw85]

If a wet and dry compression test will give false results why not just do the leak down test from the get go?

[@ALCRAN2010]

step by step grasshoppa

[@kd6tas]

There will always be some leakage into the crankcase because piston rings have gaps. Also, it's best to do the leak down test with the piston at top-dead-center because the top of the cylinder is where the most wear takes place. In other words, the leakage will be highest with the piston all the way up. An engine with a lot of wear can have a difference of .020" between the top and bottom of each cylinder. That was more common in old-school engines with cast iron blocks and nothing done to slow cylinder wear. To help keep the piston at the top during a leak down test, start with the supply-side air pressure at zero and bring it up smoothly. I've watched a number of leak down test KZbin videos. This was one of the better ones.

[@ruthdanielson919]

Excellent. Very helpful. 2006 tacoma with disappearing coolant. Leak down test. All 0% except valve #2 at 5%. No bubbles in coolant but did not state where he heard leak. Coolant continues to slowly disappear no visible leaks. Radiator pressure test 15 psi performed no visible leak at 10 minutes. Lost nearly one resovoir full in 3 months.

[@CMAutohaus]

Glad you found this video useful. Sound like an internal engine issue if there is coolant loss and no external leak.

[@ruthdanielson919]

@@CMAutohaus Right, but passed leak down test, didn't reveal an internal engine leak. Radiator pressure test while visualizing with boroscope another good test. Can dx drops of coolant at the head gasket. Will repeat radiator pressure test. Hopefully will find a visible leak.

[@MarzNet256]

Really awesome video. So, three final numbers per cylinder and a description of leak down. I just love it when someone knows what the hell they are talking about,

[@lancejonesmusic]

Awesome guide dude! Clear, professional and precise, detailed video. Much appreciated!

[@johnparson9573]

Fantastic job. Love your explanation on everything. Keep up the great work brother!

[@CMAutohaus]

Much appreciated. Thank you for the kind words

[@UntappedGarage]

Excellent info as always! I did compressions/leakdown tests on an imported engine with unknown history on the stand a few months ago. This will help me sleep because I doubted my process a bit as I was seeing 0% leakdown on two of the cylinders which I figured was impossible as there will always be some leakage past the rings. Unfortunately I had leakdown out of the exhaust side on cylinder 4 and haven't had time to dig in to see what's going on. At least I know I can trust the results.

[@CMAutohaus]

Glad you found this useful! Yes 0% is ideal, but even with 0% on the gauge you will still hear air come out the oil filler as "true" 0% is impossible.

[@TorxGarage]

Good information, would like to note you need to make sure you set the regulator to 100psi before connecting it to the cylinder. I like to recheck it each time. In the case of a Mini engine, 9% leakage is enough to cause smoking and ultimately condemn the engine. I would suspect this is why you’re getting such good readings. But still very useful information.

[@SolarMillUSA]

5% is incredible, not just fine. You *should* have some leakage, and it should be around the piston into the crankcase (just as you heard).

[@ourmandan]

really useful at this moment in my auto life. THanks

[@jeffallen6937]

This is a bit random but don't forget to drain the mioster from your air compressor. Underneath the tank you will find a little drian valve. The valve typically needs to be replaced.

[@salvadorpalma8173]

This guy: "If you don't do wet comp. test the results are rubbish" Also this guy: "For the sake of time I'm not gonna do a wet comp. test." Alright mister expert.

[@waggitnshaggit6592]

He explained why, all were really close.

[@Flatlower]

Cummins recommends checking on TDC. You can get a false reading otherwise. You wear is on top end of the piston liner.

[@gregorymammel6761]

Dude! this video was extremely helpful. Great explanations of all 3 tests.

[@CMAutohaus]

Glad it was helpful! Thanks for the watch!

[@solarchild1]

great info been used on every aircraft engine since ww2

[@79tazman]

A leak down test will do a better job at pointing the issue then a wet compression test. The engine will gain compression once running because the heat will have everything expand and will cause the end gap on the rings to tighten up too making the compression higher then a cold test

[@RyuMoto]

One of the best videos on this topic. What's the best way to do a compression test when the motor is on an engine stand?

[@CMAutohaus]

When the engine is out, we usually do compression tests when the engine is on the floor for saftey, also because we need to installed the starter and bellhousing at times. We just hook up the starter straight to a battery and crank 8 times

[@rogerlopez7490]

Great information, thank you for posting this

[@oppanheimer]

Very demonstrated and explained, thank you.

[@Bryan_One87]

I've had it happen twice now in a 43 Vortec motor and the last time it happened I now have zero PSI in cylinder 4 which I'm praying is a valve and not the cylinder

[@gee3883]

Brilliant explanation dude.

[@francisdsa6790]

Appreciate your testing method of compression of engine and demonstration thanks brother Greetings 🙏💐

[@JoseGonzalez-ew6zz]

This is the best I’ve seen. Unfortunately need to do this on my ej207 swapped wrx . I had 110,110,105, 102 psi on mine which is lower than the 125 it should be for a ver8 engine

[@JoseGonzalez-ew6zz]

I didn’t know how to do the leak down but I’d like to do it

[@johnlucala1532]

Great video,and very important topic,I just subscribed to your channel, right now...

[@CMAutohaus]

Glad you found this vid useful! Thank you for the sub!

[@ceezauto213]

Great video. I'm wondering if you can help me out with some advice. I've done so much work on this car but it still overheats. (2012 ford fiesta 1.6l) I bought the car with the engine overheating and blasting white smoke out of the exhaust. with the coolant bubbling in the reservoir. I have since, replaced the head gasket, coolant outlet gasket, thermostat, water pump and resurfaced the cylinder head with new head bolts. And properly bled the cooling system. The car still performs the same after all of these repairs. The car still passes the engine block test (same as before the repairs). And there was never signs of coolant in the oil or oil in the coolant (before or after the repairs). A compression test determined cylinder 3 had 120PSI and all the rest of the cylinders were around 110PSI (I was told by a dealer tech that the normal range was within 100-110PSi). All of the coolant hoses get hot and my heater blows nice warn air. There are no coolant leaks and the system holds pressure at 13 PSI for 10 minutes without falling down. The car idles perfectly. Why is this engine still overheating? Is it possible to have a cracked cylinder head/engine block even with a passed block test and good compression?

[@CMAutohaus]

There could be a unique way you have to bleed the system

[@ceezauto213]

@@CMAutohaus thanks still no luck though

[@CarlosSilva-gc8ny]

Podría ser el radiador obstruido, hacerle una limpieza profunda con agua a presión. Exactamente eso me sucedió y por eso lo comento.

[@pyt22fr11]

Excellent presentation !

[@juanga69]

Great video! Helpfull as always.

[@CMAutohaus]

Thanks for the support! Glad you found this video useful!

[@Priest]

@ 8:30 is that really how you perform leakdown test ? I thought you need to calibrate the needle so its right at the beginning of "set"

[@CMAutohaus]

Yes I made a mistake, needle needs to be calibrated everytime this is done.

[@ghj1502]

High praise!

[@Villagerbluewheelsunflower]

When would you do a leak down test at UNDER 100psi? Smaller engines? Different types of leaks? Snap-on was designed for 100psi testing only. Other companies can test at lower pressures. Is there a point?

[@CMAutohaus]

Depends on the tool. I've seen others like OTC spec a different pressure

[@wholewheat1]

Leak down percentage is calibrated to 100 psi because the math is simple. 100 psi in - 95 psi out = 5% leak

[@MeanDaGreenScreenBra]

Why do you need all 3? Seems like a compression test can yield good results even when there is a problem (false positive or negative? I can never remember which). What does a compression test tell you that the leakdown doesn't?

[@trevormorgan7138]

Your readings weren't zero. You have to adjust your regulator it was above 100% after hookup when cranking the engine over. Cranking the engine on compression back feeds through the restrictor on the gauge and adds pressure to the regulated side. Your first gauge is regulated pressure, your second gauge is after a restrictor and is simply observed pressure. Since your regulated pressure changed you have to subtract your observed pressure from the new regulated pressure. Zero percent is actually not realistic, there will always be leakage... You just saw zero because you messed up the gauge by cranking the engine.

[@114bdjensen13]

Ur confused with each test

[@richardpope9985]

Great observation.

[@SolarMillUSA]

@7:30 0% leak down is not ideal. Because of the gaps in the piston rings and the necessary clearance for lubrication, you will never have a perfect seal. It is so incredibly unrealistic that it means that there is a problem in the testing set up, like forgetting to remove the Schrader valve when combining parts from compression and leak down test kits. A leak down that low should be a red flag 🚩 that something isn’t right.

[@UpInSmoke54]

I think he got 0% because the intake pressure was over 100 psi, if he had adjusted the intake pressure back to 100 psi when the pressure rose on the output he would have had a deffirent result.

[@TechMechRandom]

Subscribed for the content and because of Full Metal Alchemist ;)

[@CarAholic86]

What happens if you keep turning the engine past where it gets hard? Can you damage anything?

[@CMAutohaus]

You shouldnt be able to turn it past, crank pulley bolt should get tighter first.

[@joshrawks21]

Great video

[@garrettwalraven2552]

So my 97' honda odyssey with 320,000 miles has upper and lower radiator hoses only a year old that collapse. Then the radiator empties to about a 3rd to a 1/4 coolant bottle low but while the overflow reservoir is full and overflowing at the same time and Pisses on the ground. There is rusty like sediment in the radiator and only the new cap I put on and its a tiny bit cloudy. I think this is original radiator from 1997 but I don't know it's a single one owner before me. Is my head gasket leaking or should I just overhaul and get new hoses (entire engine) new radiator, thermostat, housing,temp sensor and water pump or what? Much appreciated of anyone's help thanks 😊

[@wackey3455]

Would you be able to tell something i done a smoke test on my engine vw golf mk6 tdi i had smoke coming out of the oil filler and i had oil squirting out of dip the stick. long story short i put petrol in the car twice first time i got away with it second time i dident. i was chasing low fuel pressure for a long time evening after replacing injectors fuel pump fuel pressure regulator. fuel pressure sensor. basically the kitchen sink at it. would you be able to tell me do you think the pistons ring are shot. the car starts on the button but when i put the foot down black smoke bellows out the exhaust pipe all i want to know before i pull the engine apart do you think its the pistons rings thanks in advance paddy

[@RAWRMotorsports]

Compression test should be done on a dry cold engine

[@Drew.407]

You mentioned you were listening to the cranks during the dry compression test to see if a crank is turning over too fast or skip a crank. What would it mean if it did do that?

[@CMAutohaus]

Very Low compression in one cylinder

[@Drew.407]

@@CMAutohaus oh dang. Even if the number is good relative to the others?

[@PeterHernandez-lg2eh]

Leakdown covers it. Smoke for vacuum pressure for coolant ,leak

[@jimlamb5508]

If you are going to do a video, use an engine with a problem. It was a good video, but MY ENGINE conclusions were drawn immediately after the wet test. still low compression after oil, leaves only the head whether it is a gasket or valve, the head must be removed. I will do the leak test just for curiosity, but suspect the valves leaking (90%) or head gasket (10%) being left out after a rebuild. (That i did not do) I will not look for the place where both valves are closed either, just remove the rocker arms. dry 90psi, wet 120psi so it must be head related? Leaking sound is LOUDEST at valves, I don't believe i need a leak down

[@CMAutohaus]

When I get a "bad" test I'll make sure to film it. Thank you for the feedback!

[@isamal-barghouthy3838]

re the air compressor, is there one that is good for mechanic work as well as body? i intend to use it at home. I tried to use a small huskey but it runs out of air too quickly

[@chasereeves8977]

How did you get the Hks oil splash pattern on the valve cover? That’s sick!

[@CMAutohaus]

Painted myself. Each color is a different layer masked off. I think you can hydrodip these days - much easier

[@mikemike4737]

what if you hear air coming out of a another cylinder next to the one you are testing. Could it be a head gasket?

[@CMAutohaus]

Correct. Or cracked cylinder head

[@mikemike4737]

@@CMAutohaus I have this prolbem in my 2005 4.7 sequoia. Misterious misfire on bank 2, the whole bank cylinder 2.4.6.and 8. after checking coils, sparks, swaping coils, sparks, injectors and upstream wide band sensors from bank 2 to 1. I did smoke test, and the intake manifold gasket showed smoke out of the bank 2 on two spots, by cylinder 4 and 8. I put 5 PSI through the smoke tester into the brake booster hose going directly to the manifold and closed the throttle body hole. Maybe I put two much PSI through it? Still same misfire. Car sat for two weeks. I though, maybe a leak in the exhaust gasket. Took out mu long tube headers and resealed everything. Car sat for another week during this exhaust gasket reseal. After I was done, the Car drove perfectly for 2 days, no problem. No more P0300, P0302, P0304, P0306 and P0308. Just perfect. I thought, it must of been a exhaust gasket leak, but I did not believe that. Then after two days. Misfire again, car in limp mode just like before. Could not go more than 20 miles. Check engine flashing just like before. But this time only one code P0304. Took out spark plugs and I had ruthenium before. Went back to the stock ones, IRIDIUM. Just like the sticker on the valve cover said: ONLY USE IRIDIUM SPARK PLUGS. I thought maybe its the sparks. I put my endoscope and cylinder 4 was wet and washed. Once I put the STOCK IRIDIUM sparks back. The code changed to P0302. I performed this exact procedure you did. I put a screwdriver to just gauge the almost TDC on cylinder 4 so that when I shoot 100 psi through it then I can close the valves by just a turning the grank shaft pulley a little. I wet my hand and put my finger on the cylinder 2 spark plug hole and I could feel the air coming out in my hand. During this test there was no bubbles in the coolant. I did notice at the end that there was coolant on the floor. I did not notice it. I was paying attention on that cylinder 2 and feeling the air with my hand. I traced the coolant and it came out of the cap on the radiator but I did not notice during the test as I was so focused on that cylinder 2 sparp plug hole leak and holding the brake bar. 100psi almost lifted me up I'm 170 pounds and it was a workout holding that crank pulley. GAUGE ON THE TOOL SHOWED ZERO LEAK ON CYLINDER 4. Im pretty sure it's a head gasket leaking more between cylinder 2 and 4 and a little on the coolant galleys. There was no leakage through cylinder 6 spark plug hole. I checked numerous times. WHAT DO YOU THINK? IS IT A HEAD GASKET?

[@florenbaron7111]

My engine only shakes after warming up. Can someone tell me what it might be? I know there are some smart people here. The vehicle barley moves when pressing the gas, smoke or steam coming out of the exhaust pipe, etc. The water pump went bad and I replaced it. I think I had a blown head gasket. I used gasket sealer and the smoke reduced almost completely but when I first turn the vehicle on a puff of smoke comes out. No check engine light. The temperature guage does not go up enough when my scan tool shows a much higher temperature. The engine is knocking. When I remove the upstream oxygen sensors I hear something like clunking or air quickly releasing from the exhaust valve when it shouldn't, on the side that shakes the most. I would really appreciate advice, suggestions, etc. Thank you.

[@kennethmabus381]

Nice video!

[@CMAutohaus]

Thanks for the watch!

[@dennissytsma3561]

I agree with what you said, must do all 3 tests. Do you like to do compression test at normal operating temperature? Nice video.

[@CMAutohaus]

I go by the FSM. They differ between engines ie S2000 Honda wants you to perform the tests on a cold engine.

[@stephenburnage7687]

@@CMAutohaus I was taught that the cold test is the more accurate. As the air gets warmer, the pressure increases (Bolyes law). Also, metallic components expand, closing metal to metal gaps. A cold test is therefore the purest test but there is no reason why you cannot undertake both cold and warm tests. There is a YT video of someone who had good readings on all cylinders on the warm test but had one cylinder seriously bad, at only 70psi, on a cold test, indicating the early onset of a problem.

[@tl-ec4pl]

Hi CMA! Thanks for this video been trying to purchase a 20v BT but a lot of engine importers tell me they can only do the compression test after payment and they cannot do the leak down test when an engine is outside of a car. This been holding me back from purchasing. Do you know of any 20v BT engine importer that can do all the things you've mentioned in this video that can ship to Washington?

[@CMAutohaus]

I do not, but that sounds pretty bad on the engine importers part. We do compression/leak down on engines outside the call regularly. Also have had customers buy engine with a compression/leak down sheet attached. I think 20v engines are so in demand these days, importers dont even need to bother with a comp/leak down because people will pay up the arse reguardless.

[@Suar5379]

Hey brother quick question if that’s ok did dry test two cylinders at 135 (1 and 2) and 185 (3 and 4) wet test (1 and 2 ) when up to 185 problem with the block…? But what are the chances to be rings only….? Car over heat I did the head gasket leak test was 100% good nothing on the radiator the car is a mini 2011 1.6 nine turbo. Thank you

[@RAWRMotorsports]

How much u charge for all 3 tests per cylinder ?

[@R3ddyyg]

My car is burning oil, but being a Focus mk1 no shop really cares about it, they all have the shop full of suv or more expensive cars... So i decided to do compression and leak down test myself, the compression it's very good and tomorrow i'll do the leak down test, i'm thinking my oil is dripping from the valve stems seals how could i hear it? From the intake? Vacuum line?

[@CMAutohaus]

Leaking valve stem seals should cause smoke to come out the exhaust on hard accel or decel.

[@R3ddyyg]

@@CMAutohaus Idk why but i have whitish smoke coming in the cabin on hard acceleration and i notice it on decel on the back, the test didn't show much tbh, 15 to 20 on all 4 cyl, i'm rebuilding the top end in a month and will keep adding oil in the meanwhile... Might be a headgasket. I'll do headgasket, rings, valve stem seals and more, i have a miata as """backup""" so i can still go to work and get groceries 🤣🤣

[@limamantapachitas]

I would do it when the needle spikes for 3 time

[@never2enuf]

Keep looking if you want to accurately conduct a leak down test. This guy's method is absolutely incorrect. The title is correct, "DON"T MAKE THIS MISTAKE".

[@dalebabbitt6185]

Curious, what was incorrect? Thank you.

[@DidiLeeReco]

When I saw that he did the test without setting the tool gauge to zero first I stopped watching it. You have to calibrate the gauges before you do any test otherwise will give wrong reading.

[@snguyn796]

lol gtfo. His method is correct

[@DidiLeeReco]

@@snguyn796 then you are a stupid and retard brain! First because the method is not 100% correct second for using inappropriate words.

[@bobbyhill4460]

@@snguyn796can I use this method instead of finding tdc on a v8

[@bradleywesterford3587]

couldn't you just have pulled the EFI main to disable the fuel system instead of unhooking the fuel pump?

[@S7RING3R]

Wet compression test on subaru motors, how do you make sure the oil poured into the cylinder coats the whole piston ring? Do I just turn the motor over and that will be enough movement to coat the rings? Also, is it okay to do a compression test on a motor outside of the car that doesn't have oil in it?

[@andiminthegarage7081]

I have a vw beetle boxer engine, and I used a long nosed air gun to move the oil around the cylinder. Seemed to work OK.

[@cagr0311]

Do u take all plugs out or one at a time

[@Bryan_One87]

Does anybody know what can cause an engine to suddenly start eating spark plugs

[@squaresquare5883]

what size is your compressor

[@badbug911]

Which model snapon leak down tester is this.

[@silicondt1]

When you do compression and leak down do you leave all spark plugs out or put them back in as you go?

[@CMAutohaus]

Leave them all out the entire test

[@jantelow]

How to test oil rings ?

[@LTVoyager]

Note to self: Don’t use a wrench to tighten the oil fill cap next oil change.

[@3gcraftsman]

I did dry compression and one cylinder was 15psi lower than the rest. I did a wet compression on that cylinder and brought it up to exactly the same as the other cylinders. Anything I can do to improve or just let it ride?

[@CMAutohaus]

15 psi isnt much. Id do a leak down and see where the compression loss is comming from.

[@3gcraftsman]

@@CMAutohaus thanks

[@dinto_louis]

Hi, the wet reading on one of the cylinders is lower than dry reading..what could be the inference..? I have done dry & wet compression test on my VW Polo 1.2 TDI..the reading is lower in the wet test than the dry test on cylinder number 3..? Dry: 1 - 26.7 (Bar) 2 - 26.5 3 - 27.8 Wet: 1 - 27.6 2 - 26.7 3 - 26.3

[@CMAutohaus]

I'd do a leak down test. Something may be wrong with the head or head gasket

[@BatJordo]

You hear it in the oil filler because of the Positive crankcase ventilation valve.

[@TBD3.0]

👍🏻

[@Watchout1010]

12 volt system,12 volts is a dead battery...🤔

[@CMAutohaus]

Approx 12.6v is a full battery. 14.7v is charging system volatge. Some cars wont even start with a battery with 12.0v

[@DidiLeeReco]

When I saw that he did the test without setting the tool gauge to zero first on the leaking gauge i stopped watching it.

[@rickylee2477]

You didn’t zero gauges. So entire video was invalid results sir.

[@grantlloyd23]

He didn't even set his gauge for the leak down. This guy doesn't understand the system... keep looking for how to do correctly.