Spotting leaking headgaskets

[ChrisP]

Why, soitanly!

Actually, I'll let Allen W. Cline explain it...

http://www.streetrodstuff.com/Articles/Engine/Detonation/index.php

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

 

[ChrisP]

Why, soitanly!

Actually, I'll let Allen W. Cline explain it...

http://www.streetrodstuff.com/Articles/Engine/Det
onation/index.php

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

 

[CompUser]

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."

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

 

[CompUser]

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?

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

Steve

 

[ChrisP]

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

Steve

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

 

[CompUser]

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).

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