Is my Audi A4 head cracked? What to do?, Last update. 10/13. Spewing coolant. Options

[jk76.914]

I may be in a pickle. My daughter's 2004 Audi A4 1.8T, 105,000 miles, was using some coolant. I looked and looked and looked, there was no evidence of a leak. It used about a pint every 500-1000 miles, so I thought there should be some visible sign, but no. There's no symptom at all. Nothing wet, driveway dry, no smoke, starts good, runs fine....

But then yesterday, after topping it off again, I changed the plugs. The threads on the #4 plug were wet. The other three not. I'm guessing a crack from the plug to the water jacket somehow, and it probably opens up at temperature, seeping coolant into the combustion chamber.

What do you guy's think? The wet threads seem to confirm the diagnosis... Any other ideas? Anybody know if these things are prone to cracking?

Any danger in trying a Bars Leaks sealant? They're pretty well regarded, I think, and they have four products for cracks, head gaskets, etc... I'm thinking of trying the mildest first.

She commutes from Boston to Rhode Island daily, putting about 400 miles on the car every week.

Here's a picture of the 5 valve combustion chamber I found on line. Lots of opportunities here for cracks... Help!

[HAM Inc]

It is more likely that you have a head gasket failure than a cracked head.

In my 27years of cylinder head work the situation where a crack would open and leak coolant at operating temperature, but not leak at ambient temp has been so rare that I can't recall a specific incidence of it. When castings relieve themselves and crack, the crack will usually leak all of the time.

Your head may cracked, but it might be such a small crack that when the engine is cold and not running (with no coolant system pressure) that it is not detected.

It sounds like the head needs to come off. Have it pressure tested and resurface.

[r_towle]

It is more likely that you have a head gasket failure than a cracked head.

In my 27years of cylinder head work the situation where a crack would open and leak coolant at operating temperature, but not leak at ambient temp has been so rare that I can't recall a specific incidence of it. When castings relieve themselves and crack, the crack will usually leak all of the time.

Your head may cracked, but it might be such a small crack that when the engine is cold and not running (with no coolant system pressure) that it is not detected.

It sounds like the head needs to come off. Have it pressure tested and resurface.

I guess BMW 6 cylinder heads are left out of this thought...they all leak once cracked, but only at hot temps...

I agree, pull it off and spend a few bucks to have it pressure tested.

I found that you can shop around and find a head that is ready to bolt on faster than getting yours fixed...and typically its cheaper.

There is a guy in Alabama that wll ship you a head and wait for your core head.
The classic BMW crack is between the water jacket channel and the exhaust port.
It opens up at high temps and all the coolant gets burned up...so there is almost no trace of the leak till you do a pressure test on the head.

Rich