Spotting leaking headgaskets

Jim Lofgren · 2004-02-19T04:38:51+00:00

I've got a 2k Legacy OB that I'm really curious about these blown headgasketproblems. It now has 56K miles on it and has no performance problems.Where do I look to see the leaks (if they are there) I don't want to takeit to the dealer unless I have to. Fortunately we bought the extendedwarranty!Regards,Jim LofgrenRedmond, WA

Feb 19, 2004 25 Replies

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ChrisP 22 years ago

Good article.

One other thing, I believe there is an editing mistake in this paragraph, or maybe it just confuses me:

"An engine can live with detonation occurring for considerable periods of time, relatively speaking. There are no engines that will live for any period of time when pre-ignition occurs. When people see broken ring lands they mistakenly blame it on pre-ignition and overlook the hammering from detonation that caused the problem. A hole in the middle of the piston, particularly a melted hole in the middle of a piston, is due to the extreme heat and pressure of pre-ignition."

-Chris

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ChrisP 22 years ago

Hey, maybe we're on to something here, detonation (not pre-ignition), piston slap and coolant temperature (as in too high, at certain locations). Reading this article I find:

"Detonation causes three types of failure: 1.. Mechanical damage (broken ring lands) 2.. Abrasion (pitting of the piston crown) 3.. Overheating (scuffed piston skirts due to excess heat input or high coolant temperatures)" Sounds familiar to me. Maybe there is something else really going on here. Has anyone had their knock sensor replaced as a result of other service?

-Chris

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CompUser 22 years ago

I'm guessing the confusing part is the statement that "an engine can live with detonation...for considerable periods of time", and then describing broken ring lands as a symptom of detonation--? As I understand it, detonation can exist in magnitudes ranging from mild to severe...with corresponding effects on the engine, from mild to severe. With preignition, as I understand it, it's basically a fatal condition, as soon as it occurs...

Steve

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CompUser 22 years ago

Which direction are you looking, with this...piston slap or leaking head gaskets?

Steve

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ChrisP 22 years ago

I'm thinking that they're all related. The article gives a really good idea of what can happen when detonation takes its toll on the engine. The overheating can cause warping or maybe it can overheat the gasket and weaken it (my opinion). An overheated piston is certainly a problem -- very descriptive fault mechanisms are mentioned. I'm not sure I have any of the major problems but I know that my engine detonates (knocks) under quite light loads and octane will not completely eliminate it. This has occurred since the day I bought the car (Legacy GT Wgn. Feb 2001).

-Chris

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CompUser 22 years ago

Is your engine one of the types credited with developing piston slap---I've only read about it here, and kind of let it go once I got the impression the 2.0 doesn't seem to show it...

I'm not familiar with the specific locations for the headgasket failures (some guys in here have discussed it in detail), it would be interesting to see how the failure sites would match up to detonation-based overheating...

You've had knocking since Day 1? How did service dept respond to that, "it's normal"?? Keep those service sheets just in case.

Steve

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