Found out where my coolant was going... 56K Stay Away!

[HeymyAudi]

RIGHT THROUGH THE DAMN CRACKS and burning off in my exhaust... Thats why it never mixed with the oil.... Well I took these and now its off to get it welded up and 2 new valve seats.. seals etc... etc... Good thing I had now bent valves or anything just the crack... Now the question is WHAT CAUSED THIS??? I know Winston had a similar crack in his head before his build...

[absolutegtr]

I thought it was your oil cooler? Hasnt this "leak" been going on for quite some time?

You should have upgraded to a AEB head...I could have one for sale

[MikTip]

The top picture is a very common problem with 'cast' aluminum heads. Not enough material gets in there, and or cyclic hot & cold eventually causes a crack there. Seen it many, many times over the years on many VW & Audi heads.

The second picture is from a foreign object getting inside your combustion chamber, and getting smashed into the head...

Hows the top of that piston look? The rings?

[HeymyAudi]

The top picture is a very common problem with 'cast' aluminum heads. Not enough material gets in there, and or cyclic hot & cold eventually causes a crack there. Seen it many, many times over the years on many VW & Audi heads.

The second picture is from a foreign object getting inside your combustion chamber, and getting smashed into the head...

Hows the top of that piston look? The rings?

Pistons and Rings are in perfect condition but that 2nd one is just a lil wierd...

[dougyfresh]

The top picture is a very common problem with 'cast' aluminum heads. Not enough material gets in there, and or cyclic hot & cold eventually causes a crack there. Seen it many, many times over the years on many VW & Audi heads.

The second picture is from a foreign object getting inside your combustion chamber, and getting smashed into the head...

Hows the top of that piston look? The rings?

Agreed!

[HeymyAudi]

I thought it was your oil cooler? Hasnt this "leak" been going on for quite some time?

You should have upgraded to a AEB head...I could have one for sale

Yeah the leak has been going on for some while... Thought it was fixed with the oil cooler but then it came back... So I decided to pull it and found this...

[diagnosticator]

Cracks between the valve seats are common as already mentioned before. However, the coolant loss isn't from the crack/s between the valve seats, there is no cooling jacket or liquid coolant circulation close enough behind the valve seat webs, to leak through the typcal valve seat web crack, like as exists in your head casting. The existance of the crack, is actually due to the high thermal stresses that develope, exactly because there is no nearby coolant jacket. The heat absorbtion rate of the metal at the valve web, is higher than the heat conduction rate pulling heat away from the web, and the heat flow path to coolant is far enough that the metal temps at the seat web are very hot compared to the surrounding metal. If the cooling jacket was closer to the seat web, close enough that coolant could leak from the crack shown, then the web cracks would not develope in the first place, because the web would run a lot cooler and the high thermal gradient and associated internal stresses that provoke the crack would not occur

Before any repair work is attempted on the valve seat web cracks, the head casting should be tested using low pressure water, to pressurize the casting cooling jackets, and is the correct method of testing a head casting for cracking that can cause coolant loss. The cracks in the valve seat webs are not a problem according to Audi, if the width of the crack is 1 mm or less, IIRC.

[HeymyAudi]

Cracks between the valve seats are common as already mentioned before. However, the coolant loss isn't from the crack/s between the valve seats, there is no cooling jacket or liquid coolant circulation close enough behind the valve seat webs, to leak through the typcal valve seat web crack, like as exists in your head casting. The existance of the crack, is actually due to the high thermal stresses that develope, exactly because there is no nearby coolant jacket. The heat absorbtion rate of the metal at the valve web, is higher than the heat conduction rate pulling heat away from the web, and the heat flow path to coolant is far enough that the metal temps at the seat web are very hot compared to the surrounding metal. If the cooling jacket was closer to the seat web, close enough that coolant could leak from the crack shown, then the web cracks would not develope in the first place, because the web would run a lot cooler and the high thermal gradient and associated internal stresses that provoke the crack would not occur

Before any repair work is attempted on the valve seat web cracks, the head casting should be tested using low pressure water, to pressurize the casting cooling jackets, and is the correct method of testing a head casting for cracking that can cause coolant loss. The cracks in the valve seat webs are not a problem according to Audi, if the width of the crack is 1 mm or less, IIRC.

Cool I had the head pressure tested and they didnt find any more cracks in it... Now what your saying makes sense....