jerome951

Everyone,
I could use some advice as I'm stumped.

I have combustion gasses (I assume) entering the cooling system. I pulled the head and it looks fine. Headgasket looks OK. No cracks in the bores. I'm stumped.

Background:
After the last race of a club race a couple weeks ago I noticed a bit of water coming from the reservoir overflow. Reservoir was also empty. Car ran fine and temp never wavered from normal.

A couple days later I refilled the cooling system (took a gallon to top up the system and fill the reservior ) til it was full then started the engine. After a couple seconds bubbles started entering the tank and pushing the water out. I pulled plugs from cylinders 1-3 and noticed #2 was a tad cleaner than the others and I saw a small puddle of water on the piston.

Assuming the headgasket had blown, I pulled the head this morning. But, the headgasket appears to be intact. I can't see any cracks in the head or coolant passages that would cause this, and no cracks in the cylinder bores, either. The head is flat across the combustion chambers though the material between the chambers are sunken slightly (by ~0.004"). Bore tops are also flat. I bought this head as a fresh rebuild a couple years ago but don't have that much track time on it.

No oil in coolant or water in the oil.

Not wanting to reassemble everything without knowing the root cause, I'm looking for advice on what else to check that could be causing this. All ideas are appreciated.

Below are pics of the gasket (both sides) and the valve pockets. No discoloration on the head or block which would indicate exhaust gas was passing over it.

Thanks in advance,
Jerome

67King

I'd have the head checked for cracks? I think they use dye and penetrant to check, but you likely won't be able to see it with the naked eye.

JohnKoaWood

+951, this was my first thought...

Call machine shops in your area, you can also call a hospital to ask about having it x-rayd..... This is what we used to do with aircraft wheels!

jerome951

Thanks Guys,

That is what I'm thinking but was hoping for something simpler. I was hoping to get it put back together this weekend. I'll call around to shops on Tuesday.

Tom M'Guinn

Tell us more about the motor...

What head studs and how old?
How did you torque the head nuts?
What kind of engine management -- stock, MAF, etc?
How much boost?
AFR under boost?
Knock counts under boost?
What octane gas?

I've had too many head gaskets leak under boost with virtually no sign of problems when removed. Cracks and such are always possible, but odds are in favor of a more basic HG sealing issue I'd say...

jerome951

Hey Tom,

Engine, boost, and engine management are stock. I always run 93 octane but don't measure AFRs or knocks. I know it runs somewhat rich (~11.0:1), though, based upon previous dyno pull. Head studs are stock (I think original) and have been through at least 2 head gasket changes that I know of.

When I replaced the head ~5 years ago from a burnt valve I used the 15 ft + 90 degrees + 90 degrees method, reusing the old studs. All head nuts felt about the same tightness when I removed them this morning.

Tom M'Guinn

Well, if it's a completely stock motor and you've been tracking it for last 5 years, I'd be inclined to just skim the head, check the valves, etc., and reassemble. Don't think it is not the HG just because there is no obvious deformations. I have half a dozen gaskets in the garage that were leaking and look the same. You can see in the picture that the #2 valves have been steam cleaned. If things get hot enough at the top of the cylinder the block and head can expand so much that they squish the gasket even more than normal. Then when things return to normal operating temp, you're left with a gasket that's too skinny. Try running a micrometer around the #2 fire-ring on the gasket and compare it to the others. No guarantees you'll see a difference, but you might. Either way, I'd try a new gasket before resorting to more exotic testing.

Oddjob

+1.

I have had a headgasket leak w/o an obvious gasket fire ring failure, and no other noticeable leak point.

jerome951

Well Tom, you were right.

#1,3, & 4 fire rings measured a consistent 0.050" while #2 varied between 0.050 and 0.045". I'll call some shops this week to see about having the head skimmed and cleaned up.

In this case would you recommend replacing the head studs as well? I'm sure mine are still the originals and have 125k on them and 13 years of tracking.

Tom M'Guinn

Well, the stock studs are most likely just fine, especially if you are running factory boost and chips. I'd probably change them, but I always lean toward overkill. If you opt to change them, get the snap-on collet style remover and a good/big T-handle breaker bar. Those tools make a nearly impossible job merely a huge pain. From what I can tell, they used about a quart of red loctite mixed with a tablespoon of JB Weld on each stud at the factory.

jerome951

Thanks for the advice, Tom, but considering you said they're likely just fine, the difficulty w/ the engine still in the car, and a race coming up in 3 weeks, I think I'll just leave well enough alone.

I'm looking at an engine rebuild in a few years so that will be a good time to replace them.