I think I know the answer, but does this appear to be residual coolant weeping out at my exhaust? Might be time for the dreaded head gasket job, along with all of the "WYIT" stuff. Been chasing coolant loss of unknown origin for quite a while. Looks like I may have found it... Found similar evidence on the header at #2 near the head.

 

Do you have any other HG symptoms? I'd pressure test the cooling system before doing anything else. The kits sold at Sears and other places are fairly cheap and very easy to use -- every 944 owner should have one.

 

I've pressurized the system on multiple occasions looking for a leak somewhere, but found nothing... Can't imagine any other source for evidence of fluid getting pushed out of my exhaust system, both at the head and further down stream. The evidence at the head is coming from only one cylinder.

 

If coolant is leaking out the headers, then you'd think exhaust would leak too with the usual black soot marking the leak? Sounds like your fairly convinced but if still in doubt you could get a fluid tracer and confirm it's coolant coming from the head to deck joint -- and not just trickling there from some more common leak location. What head gasket do you have - stock? I've never seen a stock head gasket leak coolant externally, but have read reports here from people who said it happened to them -- though it's usually when trying an MLS gasket. If you pull all the plugs, do any of them look unusually clean and soot-free -- suggesting they've been steam cleaned by the hot coolant?

 

Haven't seen any soot corresponding to a leak that would let the coolant out, but there is no evidence of the fluid running down from a different origin either. The residue at the head appears to be almost certainly coming from direct from the cylinder.

Will pull the plugs and have a look as soon as I have the time. Will also try to have a look into the cylinders to the extent possible while I have the plugs out to check for residual liquid on the piston.

Thanks for the help, Tom. I appreciate the inputs.