In this video I show you how to use the Pico Scope to not only find out your vehicle has a blown head gasket but it will tell you the exact cylinder(s) that is having the problem. Why is this important? It is best practice to grab all the data you can before you tear the vehicle apart so you know what you're looking for in the case where it is not obvious.
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99 thoughts on “Blown head gasket? on what cylinder though….”
  1. Avataaar/Circle Created with python_avatars bovabova says:

    I miss the videos where we went to junkyards for parts

  2. Avataaar/Circle Created with python_avatars Sean Apfelbach says:

    Easy peasy. Do a block test. If the blue turns yellow then you know.

  3. Avataaar/Circle Created with python_avatars Brad Petersen says:

    I devised a lower tech version of this head gasket test and never had it fail me.
    Back in the day, we’d yank all the plugs out, put the cooling system pressure tester on the radiator, pump it up, wait a while , then bring a shop newbie over to watch the spark plug holes while we cranked it. Needless to say, our shop newbie got a shower.
    That test was somewhat crude and not terribly conclusive, as the differential pressure between combustion chamber and atmospheric was only about 15psi. II found that if I took all the plugs out, filled the radiator neck until it was starting to spill out, took one of the plugs and put it back in and cranked it. Now the differential pressure between combustion chamber to atmosphere could be 175 psi, making even a slight gasket leak show up, and would cause the radiator to overflow, as the combustion gases were being pushed past the gasket. If the radiator did not overflow, yank the spark plug out, and put it in the next cylinder and crank it, repeating the same test cylinder by cylinder. Left all but that one spark plug out to allow a faster cranking speed.
    5-time re-certified ASE Master Tech
    35 years now behind me (now retired)

  4. Avataaar/Circle Created with python_avatars peachees says:

    Pico training was so interesting and cool and we were so pumped to use our newly taught skills. And 10 years later, I've only used it twice and I don't think it was even necessary. Most tech maybe used it 1 time after training. Even our foreman use it mainly to document reading for the factory engineers to look at.

    Most electrical diag is done by checking for known "good" power and ground and if so, it must be a bad electronic part.

    For ignition work, we just mark and swap parts to see if the problem moves. For headgaskets, we just pressurize and use the scantool to see which one is misfiring and then borescope it to confirm.

    Even for hybrid system, I've yet to use Pico to diagnose concerns. It's mainly an engineer thing. We don't have access to the array of known good graphs and simply don't have the time to produce known good graphs on every part of every model vehicle.

    Even Scanner Danner had Pico diag lead him astray. He had a nonideal graph causing him to prematurely condemn a part when it was something else. Pico is a slippery noodle indeed.

  5. Avataaar/Circle Created with python_avatars Dave Scruton says:

    This test should best be performed with one in cylinder 2 and then only 1 in cylinder 1 to actually see if they as well are giving pressure. The method you used did not prove they are not leaking by.

  6. Avataaar/Circle Created with python_avatars Lou Sassle says:

    I’m always learning newer and better ways to use my pico scope. Nice Job on showing us this diag method!

  7. Avataaar/Circle Created with python_avatars Andy Saunders says:

    Sorry – plug, not bank…
    Jad a Camry 5S-FE that drove well all the time, but lost coolant quite a bit.
    New radiator didn't fix it.
    Head gasket, (after about a year), got done.

  8. Avataaar/Circle Created with python_avatars Andy Saunders says:

    Want to say that generally the plugs get washed when the HG goes.
    Good on you for checking the other bank.

  9. Avataaar/Circle Created with python_avatars Jon Bingham says:


  10. Avataaar/Circle Created with python_avatars Charlie Lambert says:

    In these cases, if need to keep on the cheap… KSeal Ultimate generally takes care of the “sipping” of coolant

  11. Avataaar/Circle Created with python_avatars William T. Musil says:

    Hiya Eric

  12. Avataaar/Circle Created with python_avatars Jon Bingham says:


  13. Avataaar/Circle Created with python_avatars Sugar Chateau says:

    Welcome back the Self Made Auto Channel. Makes me laugh every time.

  14. Avataaar/Circle Created with python_avatars Justthe Truthtv says:

  15. Avataaar/Circle Created with python_avatars John Cunningham says:

    Hopefully it IS the Gasket and not the Head or worse yet The Block .

  16. Avataaar/Circle Created with python_avatars Swallow Inn says:

    Hi Eric you have done it again. Taught your audience a valuable lesson. You really underestimate your talent for simplyfing what could be a difficult concept to understand. I expect the driver does not frequently drive long distances at Highway speeds 2 hours or more. If he did I would expect he would have temperature issues showing up. Keep up the good work. I just wish I could do it because you can do it.

  17. Avataaar/Circle Created with python_avatars Thinman says:

    Great diagnostic. Please do share with a quick follow-up video if the head gasket shows the leak channel and if there is a difference in piston top appearance between the leak and non-leak cylinders. Thanks!

  18. Avataaar/Circle Created with python_avatars jeff caleca says:

    For many years I used an old compression Tester that worked great

  19. Avataaar/Circle Created with python_avatars Dave James says:

    Ya thats a cool tool I believe they also make a head gasket leak test kit, it's a dye thing that tests for exhaust gas in the coolant. But you pin pointed between 3,4. Now you know exactly where to look, Nothing feels more wrong than unbolting a head and you can't find the blow out. . Love your way of going about things, let's now hope it's visible and not a Crack in the cylinder or head! Hope we get the k series head gasket video.

  20. Avataaar/Circle Created with python_avatars methanial73 says:

    I'm curious as to how this happened? Stuck thermostat? Blew a hose and kept driving? Water pump going bad?

  21. Avataaar/Circle Created with python_avatars James Pearce says:

    Great test. I guessed 3 and 4 too. But you had it dead on. Grest work. How many miles on the car?

  22. Avataaar/Circle Created with python_avatars Joe Craigslist says:

    Could the pressure build up have been seen with just a cheap pressure gauge? No need to have a transducer and Pico. One psi should be visible.

  23. Avataaar/Circle Created with python_avatars Rick Brodston says:

    The building AC says show the head job. Subaru does it too.
    Want your opinion on gaskets.

  24. Avataaar/Circle Created with python_avatars Derek Simenac says:

    Knowing which cylinder that is leaking is a necessity when the engine has 2 banks unless you are going to do both head gaskets

  25. Avataaar/Circle Created with python_avatars Ed David says:

    You don't have Ivans pressure transducer?

  26. Avataaar/Circle Created with python_avatars George Reiss says:

    I don't know where the coolant passages are but maybe by the exhaust valve?

  27. Avataaar/Circle Created with python_avatars Bryan George says:

    As soon as you showed the graph for number 3 I figured it is leaking between 3 and 4 and I guessed right. Great job ! It is to bad all mechanics aren't that thorough in their diagnostics. Maybe they don't want to or maybe they don't know how. I came across your website looking for a problem of my own after having my 03 Chevy stall while pulling my boat. that was my fuel pump connector. When I did the fuel pump I noticed my power steering was having issues and installed a new pump. I drove a 100 miles from home and the truck died in the middle of nowhere and had to be towed. I searched and searched and came across your website and found a video about a truck intermittently stalling after replacing the power steering pump. You found it was a bad ground for the ignition coils that grounds to the block near the power steering pump. That was my problem and I thank you for the solution. That happened last year and I have not had any more issues.

  28. Avataaar/Circle Created with python_avatars Steve Tuttle says:

    Nice piece of work!

  29. Avataaar/Circle Created with python_avatars Larry Blowers says:

    That can be important on a split engine like a subaru or other v type engine if time or funds only permit only doing one side,

  30. Avataaar/Circle Created with python_avatars Kerry Clark says:

    Show us the head gasket tear down and replacement. That would be a cool video!

  31. Avataaar/Circle Created with python_avatars A Smithh says:

    Assumption without taking engine apart. Pulled many heads finding a head gasket was sealed and there was a crack in a valve seat/water jacket. Yes head gaskets are the most common culprit!

  32. Avataaar/Circle Created with python_avatars Rick West says:

    Have you ever tried this with a rubber glove and rubber band?

  33. Avataaar/Circle Created with python_avatars A Smithh says:

    Voting NO ON EVERYTHING and yes on nothing sends the only message that WE are tired of INFLATION!!!!!!!!!!!!!!!!!!!!!!

  34. Avataaar/Circle Created with python_avatars Unknown says:

    Seriously impressed with your level of investigation. Back in the 70's world of flat rate mechanics it was strip it down, replace everything you see , give the customer the bill … Welcome to GM !!

  35. Avataaar/Circle Created with python_avatars tokuzumi1 says:

    You see this way more than this keyboard warrior, but I'd like to see a follow up on this to see what the pistons look like. Quite often, a compromised head gasket will steam clean the pistons. I wonder if there's any evidence of this?

  36. Avataaar/Circle Created with python_avatars VGAPR Garage says:

    This is great. Peco is an amazing tool. But if you don’t have a peco this could also be done with a pressure gauge

  37. Avataaar/Circle Created with python_avatars Cincinnatus Aurelius says:

    Simpler way is pull plugs, look at insulators. Cleaner, whiter will be cylinders getting coolant in them. Pistons will be cleaner too, which you could see with a cheap endoscope.

  38. Avataaar/Circle Created with python_avatars Dependable Auto Truck says:

    i think you were very clear on this 3 and 4 leaking and 4 was the worst one hard for me to see how anyone else could see different

  39. Avataaar/Circle Created with python_avatars wammyz says:

    How about trying to find if compression loss on a cylinder is from a valve problem or a holed piston without sticking a camera down the plug hole or removing parts?

  40. Avataaar/Circle Created with python_avatars Atiq Khan says:

    The evidence leeds you to the problem
    Nice diagnosis

  41. Avataaar/Circle Created with python_avatars Carey Wilson says:

    Awesome diagnostic procedure; you wouldn't possibly have a clone down here in Georgia, would you? 🙂
    Keep up the good work; love your videos…

  42. Avataaar/Circle Created with python_avatars Kevin Guy says:

    Myself, if it is a head gasket that is gone, Head has to come off anyway, Im going to see where the blow is as soon as it is off. But it's cool to figure it out first.

  43. Avataaar/Circle Created with python_avatars Busted Knuckle says:

    Is there a national database of diagnostic techs?

    It would be great to have you or Ivan to work on my truck…
    But I live in Asheville NC … I also know there's no listing here for diagnostic services

    Well one guy says he checks BMWs

  44. Avataaar/Circle Created with python_avatars Anthony Fermicola says:

    I used to run the car til warm -let it sit awhile -pull the plugs and crank it-you will see a mist come out from the blown cylinder.