Weekly waveform 15 - Cooling system pulse sensor test. Does it have a bad head gasket?

[@glenforehand]

That smile when you identified the problem cylinder, the feeling is great every time!😁

[@ThePracticalMechanic]

A few fist pumps are warranted on some jobs as well. 💪

[@exmotorsports]

Oh man...totally miss doing these. Amazing to see this was over a year ago now...Time flies. Great video Chad.

[@ThePracticalMechanic]

Kevin, I hope we can start back up soon. I need to find my list of tests and pickup where we left off. Thanks for watching and returning to the series after a year of my absence.

[@SchrodingersBox]

not sure how i stumbled on this but glad i did. really great video with excellent presentation quality!

[@ThePracticalMechanic]

KZbin works in mysterious ways. Thanks for stopping by fellow Coloradan.

[@8power0]

I AM USING EACH ONE OFF THESE WEEKLY WAVEFORMS EPISODES AS MY TEST PROCEDURES ,,, AND GUESS WHAT THEY ARE WORKING OUT FOR ME WITH A LITTLE BIT OF COMMON SENSE THANK YOU SOME MUCH , I JUST THOUGHT YOU SHOULD KNOW !!!!

[@mrblonde2013]

Super interesting Chad. Never occured to me to pull a sparkplug to mark a cylinder on a relative compression test. Thank you.

[@NorincoKid80]

Awesome video. This answered many questions I have about pulse sensor use for coolant pressure (from headgasket) including not getting coolant in the sensor. I've destroyed 2 so far trying this lol

[@jameswasher3938]

Nice presentation. Solid reasoning. I just discovered the channel. Subscribed now. Looking forward to going back to view the other episodes in this series.

[@bartscave]

Nice captures! I was surprised to see it turned out to be cylinder 4.

[@glenforehand]

Thanks for the video it really helped me out on a vehicle today!

[@ThePracticalMechanic]

Glad to hear it! Have a great weekend Glen and stay safe out there.

[@mike-yp1uk]

Great video and it good to have tools in the diag tool box. Lol

[@hightttech]

Excellent video. Very organized and informative.

[@secretsquirrel9722]

Not sure if you'll ever read this, but what's you opinion on the pulse sensor vs the transducer? I found this video trying to find an answer. A pulse sensor is super handy and cheap BUT . . . If you have sprung for the transducer, do you really need a pulse sensor any more?

[@ThePracticalMechanic]

I have several pulse sensors but I still struggle to read them easily. I find the pressure transducer easier to read because it’s displaying actual pressure where the pulse sensor shows a reaction to a change in pressure. I still use both as I am always hoping the pulse sensor readings will just click in my brain and I’ll understand it better. I also only have one pressure transducer so I normally use it for in cylinder readings and throw the pulse sensors in the tailpipe or on the intake manifold.

[@secretsquirrel9722]

@@ThePracticalMechanic Super appreciative of your time to reply and make a series of videos I have enjoyed as much as I have learnt!

[@ttstang43]

Very cool stuff, just more ways to make the same test work and possibly easier to read/understand..

[@spelunkerd]

What an interesting idea. I thought the water pump would have an ac pattern of pulsations, like ac ripple from an alternator.

[@juergenscholl2843]

Cooling systems I checked with a first or true pressure sensor did show pulsations/pressure fluctuations from the water pump and its impeller.It might be due to the chosen resolution that nothing is seen in these captures?

[@theGADGETSplaylist]

good stuff, Chad!

[@darwinmejias3449]

Thanks.

[@IamReadyToRock]

thnks

[@gooe9561]

You know, it's bizarre to me that most manufacturers do not incorporate scope use in the recommended diagnostics at dealerships.

[@trublue2319]

Great video

[@timothymohammed919]

Question: If you individually remove each plug and at some point you get no spike on the cooling system pressure.... would that help you identify the bad cylinder???

[@timothymohammed919]

oops I was commenting as i watch the video lol

[@ThePracticalMechanic]

@@timothymohammed919 Absolutely. Some vehicle will be difficult to remove spark plugs if they are located under the intake manifold but if we can locate at least one spark plug we can get a reference. If we can get to all of the spark plugs we can isolate the problem by removing one plug at a time. Thanks for stopping by.

[@tetttettamilli6761]

Just a few questions: (1.) While it wouldn't have been as accurate, nor as detailed,, could an exhaust gas meter be used: checking for any exhaust gas in the coolant overflow reservoir? (2.) Was that the 1MZ? (3.) That crack in the head, between exhaust and intake valves, was almost undetectable, wouldn't cylinder head warpage also occur?

[@ThePracticalMechanic]

I do often use the 5 gas analyzer to check for hydrocarbons and carbon dioxide in the cooling system but a recent discussion with Dennis over at The Gadgets Playlist has me wondering if the 5 gas readings are accurate when used on a cooling system. This test confirmed the head gasket failure without a doubt and gave the information require to do a deep inspection of the suspect cylinder. This was on a 1998 Toyota 4Runner with a 5vz-fe 3.4 liter. The vehicle was overheated last year when the head gasket failed. We sent the cylinder head to the machine shop for machining. Neither myself or the machine shop noticed the crack at the time. I suspect the crack was there but was much smaller at the time. Many heat cycles and a year later the crack has developed into the issue we have now. I didn’t even bother to check the head warpage since the heads are getting replaced. Luckily we have a core engine with good cylinder heads. Fully inspected these ones and found no issues with valves or cracks.

[@tetttettamilli6761]

Would an initial check for head warpage show deformation/warpage, if said hairline crack developed due to overheating? Maybe magna fluxing would've found the crack where the naked eye couldn't. And as far as the 'gas detector': a simple $35 hand-held combustion gas detector (with sensitivity adjustment)? Lastly, would a pressure inducer in the tail pipe show which cylinder was lagging? Or, if you put the crank on a channel, u'd see which piston/cylinder would be a drag compared to the others?

[@ThePracticalMechanic]

I’m sure magna fluxing would have showed the hairline crack. I’ve done dozens of these engine over the years and this is the first crack I’ve seen so we didn’t send the original heads out to get magnafluxed. I will still continue testing with a gas analyzer to determine if the results are accurate enough to call a head gasket based on low levels of CO2 and HC. It is possible that HC can be introduced to the coolant system unintentionally with additives for better cooling or even stop leak. CO2 should only be present if combustion gases have entered the cooling system but it is possible that the steam or antifreeze vapor can skew the readings? Most gas sensor available on the market for electronics diy builders have one analog output channel but the sensor responds to several different gasses. CO, and Propane are listed on the same chart for one sensor but Gadget Playlist found that the sensor responds to CO2 even thought it wasn’t listed on the spec sheet for the sensor. Does my $3000 Snapon analyzer use better sensors? I would assume that it does and it uses several different sensors. Every two years I have to send it in to get the oxygen sensor replaced. I think the pulse sensor in the tail pipe would only pickup the initial misfire on startup. The relative compression test show minimal differences between cylinders so the tailpipe output should be close to the same. The crankshaft signal will narrow it down to two cylinders if you knew where cylinder number one is located on the crank. I think the missing tooth is 40-50* offset from TDC #1. Cylinder 1 and 4 are companion cylinders and both will be at the top of the stroke at the same time. We would need a camshaft position signal to determine location of cylinder #1. Great questions and discussion. Discussions like this is how we each challenge each other to grow and learn new things. I will measure the warpage when I get to the shop today and see if the heads have developed new warpage since the machine work was performed last year.

[@OLDSCHOOLROGUE]

I have a question about pulse sensors. I purchased a Zeus and am going to buy a sensor. I find several available at various prices. Which brand do you recommend? I realize they are all built with the same components. I’m curious about quality of workmanship and quality of the internal sensor.

[@ThePracticalMechanic]

The first look sensor was one of the original ones on the market but they are more expensive than most so I have never purchased one. Cody’s auto diagnostics and jarhead diagnostics both make a variety of 3D printed pulse sensors in different Colors and connector options. Either of those are going to be the cheapest pre-made sensors. Automotive test solutions also makes some but I have not used them. Some choose to make their own sensors by placing a piezo speaker/transducer inside a small section of pvc pipe. By time you buy all the materials to make just one and spend the time assembling I would just buy one from Cody’s or Jarhead unless you already have most of the materials.

[@northpostman]

Great diagnosis, I use this method myself. The piezo pressure sensor is very simple and inexpensive to make, check out "the GADGETS playlist" for instructions. I'm surprised to see the crack location between the valves causing pressure pulses in the cooling system. That would definitely cause a misfire, but neither valve connects to a cooling jacket. There must have been either a crack between the combustion chamber and a coolant jacket or a crack in the block between the cylinder and cooling jacket. Or the gasket failed.

[@jrPort]

Awesome 👌

[@phareztrinimand]

why not also put a vacuum gauge on the radiator and see if it flickers with the pressure.

[@train4905]

Exellent😊

[@philh9238]

Do you sell pulse sensors? I been watching your vids but looking to buy one. My scope is bnc not banana jacks

[@Santiago_Ordonez_]

Exellent...!!!

[@jyao5409]

Doesn’t matter which cylinder.... the engine is toast