Diagnosing head gasket

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Diagnosing head gasket

Postby Vertigo » Mon Jul 16, 2018 11:06 am

Sup. Silvertop 4AGE 20v was running perfectly fine for a while, though it did overheat a bit when a core plug developed a hole and I had to drive it, gingerly, a little bit further than I should have. The other day I tried starting it - it fired one spark, then no more, and sounded as if all the spark plugs were removed. Some debugging later, poured a little oil into the cylinders and got it to start. Some runs later, it pours smoke out of the exhaust on accelleration.

Sounds to me like a head gasket, but Im baffled that it sounded like all cylinders were affected at the same time. Im happy to replace the gasket, but what else should I do (from home) to be sure before I dive in and remove the head?

Also, should I attempt a MLS gasket? I heard that you need to ensure smooth mating surfaces, which I doubt this thing has. Happy to put a bog standard gasket on, as it should only last another few months before I engine swap anyway.
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Re: Diagnosing head gasket

Postby RS13 » Mon Jul 16, 2018 5:34 pm

Sounds like it might have gone between pots. Have you checked the plugs? Other than a compression test there isn't much else to do that doesn't involve cracking it open.

If you're replacing the engine soon anyway I'd just stick with standard purely because I'm a cheaparse haha.
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Re: Diagnosing head gasket

Postby whynot » Mon Jul 16, 2018 9:59 pm

Are you losing any coolant or is there any black oily bits floating in the radiator? That was what I got when my head gasket was leaking.

On another note I have seen cars sound like they had no compression and wouldn't start until some oil or fuel was tipped down the spark plug hole and I'm pretty sure one was my 20v as well. I never figured out the cause but it was while messing with the ecu and doing cold starts.
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Re: Diagnosing head gasket

Postby Vertigo » Tue Jul 17, 2018 11:09 am

whynot wrote:Are you losing any coolant or is there any black oily bits floating in the radiator? That was what I got when my head gasket was leaking.

On another note I have seen cars sound like they had no compression and wouldn't start until some oil or fuel was tipped down the spark plug hole and I'm pretty sure one was my 20v as well. I never figured out the cause but it was while messing with the ecu and doing cold starts.


Now that I think about it, could it be caused by VVTfreaking out, pushing cam timing out, and getting stuck?
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Re: Diagnosing head gasket

Postby Vertigo » Tue Jul 17, 2018 11:26 am

This is also extremely interesting, especially as I have had IAC valve issues.

https://www.youtube.com/watch?v=sg3J4ibMkWc

Edit: Im actually more and more convinced this was the initial problem. It completely explains low compression across all cylinders, and failing to start. That it now produces smoke is something new, I think. It could now be a head gasket, or could be oil in the exhaust system from my wet compression tests. I did hydrolock cylinder 1 with too much oil by cranking over (no spark or fuel), so hope I havent broken rings, pistons, or head gasket, but it could be either of these, or just oil in the exhaust. That it mostly produces smoke on accelleration is a definite clue. Im going to try running on three cylinders, see if the smoke goes away.
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Re: Diagnosing head gasket

Postby RS13 » Tue Jul 17, 2018 5:19 pm

Interesting video, never would have thought of that! You'd think that it would start and run with throttle applied but not idle if it were the IACV?
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Re: Diagnosing head gasket

Postby Vertigo » Wed Jul 18, 2018 1:13 pm

I once managed to get my turbo 16v to run, poorly, with a boost leak tester blocking the intake. Helped that there were still a few leaks, though!
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Re: Diagnosing head gasket

Postby Vertigo » Sun Aug 05, 2018 9:21 am

Ok just to finish this topic off, the car fixed itself - no more smoke. Im guessing it was simply oil in the exhaust. Runs perfectly fine now, no coolant used, etc. Hmmmm.

Swapping the engine anyway!
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