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Head gasket leak symptoms?

Ecomike

NAXJA# 2091
NAXJA Member
Location
MilkyWay Galaxy
For those engine/mechanical gurus out there, if one had a single specific head gasket leak only between two adjacent cylinders, namely #4 & #5, and no other head gasket leaks (no coolant in the exhaust, no coolant in the oil, no oil in coolant, no blowby, or oil in exhaust) what symptoms would you expect see in how the engine runs?
 
Depending on the size of the leak I would think it would cause bad compression in those two cylinders. That would probably cause a general poor running/loss of power. Also i read somewhere that a rough idle can be caused by having low compression in a couple cylinders.
 
coolant in the oil and oil in the coolant or as nrl06 mentioned, do a compression test. if both 4 and 5 are abnormally low compared to the rest, then you've verified a blown head gasket.

so what makes ya think ya got a blown hg?
 
ocalajeeper said:
coolant in the oil and oil in the coolant or as nrl06 mentioned, do a compression test. if both 4 and 5 are abnormally low compared to the rest, then you've verified a blown head gasket.

so what makes ya think ya got a blown hg?
Let me re-phrase the question!

If one had a single specific head gasket leak that was only between two adjacent cylinders, namely #4 & #5, and no other head gasket leaks (no coolant in the exhaust, no coolant in the oil, no oil in coolant, no oil blowby, and no oil in exhaust) what symptoms would you expect see in how the engine runs?

I am not asking how to verify it! The premise is that there is no oil leaking into the coolant, no coolant leaks anywhere, no overheating, no oil blowby, no oil in the exhaust, and no gas in the oil, just a single head gasket leak only between the #4 & #5 cylinders.

What symptoms of that single specifc leak would you expect to see, and what symptoms would you not expect to see?
 
main symptom would be oil in the coolant and/or coolant in the oil. depending how bad its blown, could overheat, could cause bubbles in cooling system (if you took cap off while idleing to observe), could be a slight stumble in acceleration/ cruising, or nothing at all. if you want a more accurate answer, break out the compression gauge, its the only way to accurately diagnose a blown hg when oil/coolant isn't mixing unless you pull the head. if you aren't overheating, if you aren't noticing bubbles and you have no coolant in the oil and no oil in the coolant, then chances are its not a hg. very very very rarely, almost impossible to have a blown hg and no mixing of coolant oil or bubbles while running.
 
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ocalajeeper said:
if you aren't overheating, if you aren't noticing bubbles and you have no coolant in the oil and no oil in the coolant, then chances are its not a hg. very very very rarely, almost impossible to have a blown hg and no mixing of coolant oil or bubbles while running.

I had a hard time beliving it was a head gasket....etc, but I have been told otherwise, specifically I was told that the head gasket directly between two adjacent cylinders, and only between the two adjacent cylinders can be damaged thus causing loss of compression for both cylinders, with out any loss of coolant, oil, overheating, bubbles, etc. I was also told that it is not that uncommon. He is a friend of mine who has rebuilt many engines before. Basically I am talking about the thin head gasket section that seals one cylinder from the other where they are closest together, and where there is no coolant or oil port between them.

So, once again, assuming this is the case ( no matter how rare), what engine operating symptoms would one see? Sorry to bit a bit hard headed on this, but I want to get about 6 good unbiased* answers to MY question before I list the actual symptoms I have seen, and explain why I am asking the question, or answer questions to my question, that do not answer my question. By unbiased*, I mean I don't want the answers to parat my symptoms, so I am not posting the symptoms, yet.

nrl06,

Where did you hear that poor compression in 2 cylinders would cause a rough idle? On the poor running/loss of power, would that be at idle, low end power loss, and or high end power loss, can you be more specific. Would it cause rough running at all speads and loads, or just a rough idle???? So far you have my attention!!!!!

Where are 5-90, Mud8, Lawsoncl, DrDyno...etc when I need them? :rattle:

Come on guys, this can't be that tough a question!
 
Just a guess I've never seen a motor leak between two cylinders. Most of the head gaskets I've seen have a metal (steel or brass) crush ring built into the gasket that seals the cylinders. the chances of two of these rings blowing in adjacent cylinders is slim. But If I've learned anything along the road, it's that most anything is possible, just some things more likely than others.
I'd imagine seriously low compression in two cylinders would act about the same as no spark for those cylinders. More noticeable at low RPM's, and likely during high vacuum (deceleration), with a loss of high end RPM's.
Most of my head gasket problems on the 4.0 was either oil or coolant seeping out of the motor, noticeable someplace on the head to block seam seeping to the outside of the motor. Rarely coolant into oil or compression into coolant etc.
A motor that has been hydro locked (water sucked into some cylinders). Is subject to significant and often strange damage. I had one motor that bent a valve at the crown, the stem was fine the connecting rods were fine, rings weren't damaged, the head gasket did seep a little oil to the outside of the motor afterwards.
I've seen a bunch of 4.0's with piston damage, fairly common here (the autobahn) no speed limit. Driving at near full throttle for hours, burns pistons and/or the mix runs too lean and other bad things happen.
Water damage to motors I've seen has included broken rings. Scratches can often be seen through the spark plug hole on the cylinder walls. Bent valves, either the stem of the valve head. And bent rods, that if ignored will eventually totally fail and damage the block. Occasional, fluid seepage from the head to the outside of the motor. Once, coolant seeping into a cylinder and exhaust gasses in the coolant.
 
If you've got a compression/combustion leak between two cylinders, you'll probably notice the loss of power first. If you have emissions testing, you'll also notice an increase in HC and CO, since combustion efficiency tends to increase with CR (and HC and CO are signs of inefficient/incompleat combustion. NOx has to do with combustion temperature, not combustion efficiency.)

Mud - I know what you're talking about with the "crush ring" in cylinder head gaskets, but it's not much. Hell, it's usually either sheet aluminum or thin sheet CRES - if it's too solid, it won't crush. It's mainly there to protect the organic gasket composition - but once it starts to burn through, the gasket isn't far behind. I've seen "inter-cylinder" compression leaks before, so I'm quite sure it can happen. I think it would be caused by a small particle of carbon being wedged between the cylinder head deck and the block deck, then held to a "red heat" for some time (I've seen it a couple of times - interestingly, it happened on engines with EGR valves. I never did like the idea of the EGR...)

Hydrolocking damage has a simple cause - gasses compress, liquids do not. Since the engine is trying to compress water, you get the "irresistable force meets immovable object" problem - and something's got to give way. I actually saw (only once, and it wasn't an engine I was working on at the time...) where an engine was hydrolocked - and the head gasket was on the way out. We found bits of the head gasket in the oil drainback path, and chunks were in the two cylinders also affected when we pulled the head and drained the engine. That failed head gasket, upon inspection, was the total damage - the rest of the engine simply needed "clean-up" work. Now that was an oddity...

Everything in the universe has a fifty-fifty chance of happening - it either will or it won't. Period.
 
Ecomike said:
Where did you hear that poor compression in 2 cylinders would cause a rough idle? On the poor running/loss of power, would that be at idle, low end power loss, and or high end power loss, can you be more specific. Would it cause rough running at all speads and loads, or just a rough idle????
In automotive theory class, they devoted a hundred hours to engine harmonics and balance. A significant problem in most motor designs, less so in the in line six.
All those counter weights on the crank shaft, the thicker main bearings at certain spots om the crank (max thrust) and even the firing order is designed to minimize vibration.
Having two cylinders firing weakly or not at all has to have some noticeable effects. Likely much the same as disconnecting two spark plug cables and going for a drive.

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Running a motor with (undesigned) vibrations, causes bad things to happen. Like uneven thrust to the mains.

Gas is designed with additives than leave a glaze on the cylinder walls, the rings (or piston slap) in cylinders not firing, will eventually wear the glaze away, likely causing excessive cylinder wall wear.

I just took a Chev engine apart with (very) low compression in one cylinder, the glaze was mostly worn away in splotches (piston slap?) and would likely have eventually caused excessive cylinder wall wear.
 
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Well we finally got around to pulling the head off. WAPIA(B) to pull the head and manifolds all once. Luckily I had two strong helpers.

Sure enough the head gasket was blown directly between cylinder #4 & #5, and no where else. Found no other signs of damage or problems.

We also found huge 1/2 inch thick layers of dry carbon deposits in the valve rocker arm low areas on top of the head.

And we found oily sludge deposits just above the lifters on the front half of the engine, but the rear lifter area and lifters were clean!!

Now the question is why did the head gasket fail there?
 
Note what I said above about carbon particles - that probably had quite a bit to do with it.

The reason for more sludge at the front of the engine is much simpler - note how the engine "leans back" as installed. Therefore, there is more oil circulation, flushing, and drainback on the aft half of the head. Ergo, it gets rinsed more.

Wasn't that easy?:lecture:
 
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