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Evidence of blown HG?


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11 replies to this topic

#1 soobscript

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Posted 29 August 2005 - 02:15 PM

What does a "blown" head gasket look like? I think mine is blown, but I don't see any obvious ruptures or anything.
I also didn't do a compression test before tearing the motor apart. Did I actually fry a piston ring?

#2 wesley willis

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Posted 29 August 2005 - 02:26 PM

when you blow your hg, look for steam. if you have everything pulled apart and the hg looks fine, it seems logical that it's fine. i changed the hg on my old car (87 grand am), and the blown gasket was fine except for one little spot where it seemed to burn away or something.

#3 MorganM

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Posted 29 August 2005 - 02:28 PM

On mine it mixed oil and coolant, shot coolant externally out onto the cat, and in other spots.

#4 soobscript

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Posted 29 August 2005 - 02:53 PM

Out of nowhere my oil pressure went near 0 and temp almost redlined. My whole block was steaming. Oil smelled burnt (day or two after change).
Let it sit for a day. Started right up, good pressure and temp. Gave a test drive around the block, felt fine, headed home (25 miles). Makes it about 10 miles, temp starts climbing, oil pressure dropping slowly. Stalls at light, steaming/smoking like crazy.
Wait another day. Exact same scenario.
I don't know if temp went up because of no oil pressure to lubricate, or oil pressure dropped because oil got too thin from the heat.
I just don't want to get my HG/reseal job done to find out that I fried a ring and have to do it all over.

#5 MorganM

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Posted 29 August 2005 - 03:05 PM

Oil pressure and Temp will not rise/fall due to a piston ring.

Is your oil pump okay?

Water pump?

Any oil in your over flow tank? Milk in the coolant? Milk in on your dipstick?

Check other things first. However it does sound like a headgasket :(

#6 hooziewhatsit

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Posted 29 August 2005 - 03:29 PM

so you have the engine apart and are looking at the HGs?

on the wagon I just replaced the HGs on, the 'blown' portion was all black & dirty on the inner ring in contrast to the rest of the HGs being all shiny there.

#7 75subie

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Posted 29 August 2005 - 03:42 PM

is it blowing smoke out of the exhaust?if so, what color?

really white smoke= headgasket

#8 MorganM

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Posted 29 August 2005 - 03:54 PM

is it blowing smoke out of the exhaust?if so, what color?

really white smoke= headgasket


Not necesarily. That could be intake manifold gasket also...

#9 NorthWet

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Posted 29 August 2005 - 03:57 PM

Out of nowhere my oil pressure went near 0 and temp almost redlined. My whole block was steaming. Oil smelled burnt (day or two after change).
Let it sit for a day. Started right up, good pressure and temp. Gave a test drive around the block, felt fine, headed home (25 miles). Makes it about 10 miles, temp starts climbing, oil pressure dropping slowly. Stalls at light, steaming/smoking like crazy.
Wait another day. Exact same scenario.
I don't know if temp went up because of no oil pressure to lubricate, or oil pressure dropped because oil got too thin from the heat.
I just don't want to get my HG/reseal job done to find out that I fried a ring and have to do it all over.

The XT that I am currently replacing headgaskets on presented pretty much the same way: Stated it cold without problems, would ping on accelerating out of my driveway, temp gauge would start to climb and oil pressure dropped to nothing. Cooled off, and everything acted fine. When hot, the radiator was cold, even after t-stat change. Undid radiaotr cap to half on (pressure relief, and the car would go further before it would start to overheat, and radiator core was evenly warm.

What I figure is that the HG had started to leak into the water passages, but only under pressure. This pressurized the cooling system and caused it to air-lock; half-closing the rad-cap allowed the pressure to bleed and the coolant to flow.

When I pulled the heads, the HGs did not show super-obvious signs of having blown; but I could see a liitle carbon-ish streaking towards the water passages. Later, I hand surfaced the heads (not recommended way, but budget is tight) and the heads' sealing surfaces were heavily eroded where the HGs had blown.

#10 thealleyboy

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Posted 29 August 2005 - 04:19 PM

Ed:

Since you have already removed the heads, whether the gasket was blown at the time is irrelevant. The only thing I would be concerned about is whether one of the other systems (coolant, oil) failed, causing your problems. If so, that issue will have to be addressed too.

You could chance it, and assume that it was a blown HG. Some (but not all) of symptoms you describe are typical. You might get lucky - especially if you can identify another component that has failed.

But if it were me, I would get in touch with a machine shop. They have the equipment to test any of these possibile theories, whereas everyone else is just guessing. Either of the 2 shops I referred you to can give you a good opinion.

Unless you have a really good reason to think it was just a common HG failure, I probably wouldn't risk it.

good luck, John


#11 75subie

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Posted 29 August 2005 - 04:50 PM

Not necesarily. That could be intake manifold gasket also...



ohh, just never had one go on a sube, but i guess it could be if they have cooling channels.

#12 soobscript

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Posted 29 August 2005 - 07:17 PM

Is your oil pump okay?
Water pump?

Any oil in your over flow tank? Milk in the coolant? Milk in on your dipstick?


Overflow tank was full of oil 45K miles ago (10 months). Can't beat oil's freezing point in the winter!
Coolant was pure milk, occasionally with tan tint.
Heavy oil use (350-500 miles per quart) and lots of coolant use.
No evidence of coolant in oil. Except for occasional bubble on dipstick, looked like air.

Oil pump kept "normal" pressure. Water pump not weeping. Both are being replaced.

--Ed




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