Austin09

This is causing me a headache now.

The machine shop called me back. It has been pressure tested and although there is a crack, the location of it doesn't matter and its not causing any water loss.
He said the head was good, could do with a skim just probably isn't causing the water loss since its such a small tolerance just under 3 thou.

So in short the head isn't the source of my water loss.

It is definitely not an external leak. There is no overheating. I've pressure tested the expansion tank, the the coolant system topside of the thermostat is all good including the cap.

So, where do I look for water loss? One of the exhuast vales was red, so water is getting into cyclinder 2. There is no scoring on this cyclinder, slightly on #3 and i haven't inspected 1 or 4 yet.
Any thoughts? I'll inspect the block this weekend and may just skim and fill the crack and stick it back on with a new HG. Perhaps a thicker HG would help?

Tom M'Guinn

Not my "p.s." in post 8. You had a HG leak. Very common failure.

Ask the machine shop to show you this non-important crack. Sounds like something someone would say just to save face honestly.

Austin09

I could see the crack it is between a bolt hole and a water jacket. No idea how far it goes down, hence why I had it pressure tested. He said its not the cause of water loss.
The rest of the head pressure tested fine, and there is only slight distortion which needs skimming. Don't know if the ceramic coating in the exhaust valve can cause an issue?

Austin09

Pictures here.
Head was pressure tested as mentioned previously. I'm wondering if because it only happens on the turbo whether the head is fine under normal driving but draws in water under turbo load?

Voith

Crack is at 7'o clock on cyl #1?

Interesting, never seen cracked 944 8v head before..

Austin09

Crack is the bottom on cyclinder 2/3 - the middle head bolt hole and water jacket at the bottom.
Machine shop said its not causing water loss but I find it hard to believe because I have to be losing water somewhere!

Need to decide whether to skim this or buy a s/h one.

Tom M'Guinn

I can't see a crack, but compressed jpegs don't always show that sort of thing. When you say bottom, do you mean the exhaust side or intake side? Can you circle it or take a close up? If it's cracked, keep in mind that most machine shops can't test heads at high pressure. Did you ask how much pressure they used to test? A crack can often hold up to 15psi without problems, yet leak like a dirty politician under combustion pressures. If the head gasket is leaking or the crack gets into the combustion chamber (note the one mis-colored valve) then the cooling jackets in that area will see way more pressure than the shop probably used to test. I'd want to really see the crack before making a decision on the head...

lart951

I can save you the headache, 10% off any of my rebuilt heads

http://stores.ebay.com/Larts-Perform...&_sid=68335296

Austin09

I've seeked a second opinion from a machine shop. I'm wondering whether the crack opens up enough under turbo pressure to cause the water loss.

It isn't economical to repair it, however a skim may solve my problem.

Regarding the pressure testing they are phoning back today and I'll ask what psi was used. I assume you'd want 30 psi minimum?

Tom M'Guinn

Those are the types of pressures a machine shop will normally use -- something above 15psi anyway, since the cooling system is only designed to hold that much pressure. The problem is if the crack is exposed to the combustion chamber pressures for any reason then testing the crack at low pressures like that is of almost no help.

I would still be interested in seeing a picture of the crack. Have you seen it with your own eyes? If so, I give serious thought to replacing the head. Cracks only get worse on their own, never better.