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cbman 09-15-2010 09:09 AM

Head Gasket Leak
Like the title says I have a head gasket leak on my Turbocharged Zetec Cougar. Oil film in coolant reservior, Coolant in oil pan, moisture in cylinders, and pressurized coolant system are all of the tell tale signs I have. It got to the point where the car wouldn't start, which I think was caused by the moisture in the cylinders.

So, I wanted to ask if anyone has any suggestions as to what might have caused the leak or what I could do to help prevent it. I am running about 16psi max boost on a 8.5:1 C/R engine with a Cometic gasket and ARP Head Studs. The head studs were never "re-torqued". I received an email response from ARP saying that depending on the head gasket I may be required to do a re-torque after the engine has been brought up to temp and cooled down, and they definately recommend re-torquing anyway.

There was only about a tablespoon worth of coolant in the engine oil, so at this point I think I am going to just try re-torquing the studs. In the email the ARP rep said to torque to 60ft-lb with ARP lube and 70ft-lb with 30wt oil. These numbers don't seem entirely consistent with what I have seen on here and the jet.

Mother Focus 09-15-2010 10:51 AM

Did your engine heated some time before the leak? Or the block shaved for the build?

Obocecha 09-15-2010 11:11 AM

I used ARP studs in my '85 Supra turbo build. I don't remember them ever saying to re-torque the studs but that was 8 years ago. You have to remember that studs have significantly more holding power then bolts and therefore don't require as much torque. But I would certainly check to see if they have loosened at all. You might be able to get away with a re-torque.

WD40 09-15-2010 11:46 AM

Moved to the Forced Induction Chat forums. [;)]

redZX300 09-15-2010 12:03 PM

I never retorqued mine, and have not had a problem at about 7000miles boosted 22lbs. I believe it was moly lube we used on mine. not sure if that's what it was, but supposedly requires no retorquing if you use it.

Have you taken the head off to see if they loosed or if maybe your head gasket actually blew?

Always let the engine warm up to temp before boosting?

cbman 09-15-2010 12:29 PM

I have not taken the head off yet. I was planning on re-torquing, putting in new fluids, and seeing what happens.

Can an MLS head gasket necessarily "blow"? Could it leak but not be blown?

redZX300 09-15-2010 12:45 PM

Someone else will have to answer that one.

Peregrine 09-15-2010 02:22 PM


Originally Posted by cbman (Post 3408105)
I have not taken the head off yet. I was planning on re-torquing, putting in new fluids, and seeing what happens.

Can an MLS head gasket necessarily "blow"? Could it leak but not be blown?

How clean was the surfaces of the head and bottom block before you sandwiched them together?

bradshsi 09-15-2010 02:37 PM

A few points:

Retorquing is required if some of the preload in the head/gasket stud assembly has been lost. The whole goal is to have the assembly under sufficient preload so that the gasket stays in contact with the block and head while in operation. If you have insufficient preload, you will get leakage.

There is no harm in checking the torque on your studs after reassembly and cycling the engine a few times. A new gasket will relax to some extent as will new studs. Both these things will result in a loss of preload (which will exhibit itself as a loss of torque). The amount the gasket relaxes will depend on the gasket design and how hard you run the car.

The type of lubricant used on the studs has no influence on whether you will need to retorque. The stud lubricant only influences the coefficient of friction between the threads which in turn determines how much of your torque is turned into preload.

For similar geometry (length, diameter) and material, there is no difference in the "holding" power of a stud vs a bolt. Each will have the same spring rate and yield characteristics. Each will require a similar torque to seat it since in both cases you need to torque against the thread friction and the surface contact between either the underside of the nut or the underside of the bolt.

cbman 09-15-2010 03:37 PM

Thanks, you must be an engineer.

As for the surfaces, the head was milled/surfaced and the block deck was just cleaned to a smooth surface.

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