QuestionQUESTION: I've had a problem for sometime now in my 99 STS with the Northstar 4.6 I replaced the waier pump about 6 mos. ago because it was leaking and thought that would take care of it. now that it is warmer, its always on the virge of overheating, and sometimes does. I thought maybe the rad tubes were pluged, as spraying water through the condenser seemed to help, and now I am cleaning the inside with Zerex Cleaner. Now I have doubts that is going to help, and was wondering how to tell if the flow is ample. The fans are coming on at presumably the correct time, and go into high mode ok. I've replaced the pressure cap on the expansion tank, as there is no rad cap. It seems it has to be either plugged rad, or not flowing enough. What are your thoughts ?
ANSWER: Small head gasket leaks leaking combustion pressure into the coolant chambers thus causing a coolant flow restriction.
Very common fault.
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QUESTION: Unbelievable they would make such an expensive car, so vulnerable to this problem ! I guess my next step is to ck for sure by pressurizing each cylinder to specifically locate the problem cylinder. I guess Napa has an additive that would show the gases present in the coolant, but to me, I'd rather know exactly where the problem is. Would that be your approach ? My ability to repair this problem has been hampered by a physical disability, but that has also hampered my financial ability to have someone else do the repair, so I'm more than likely going to tackle this myself. From your experience, can this be done with the engine in the car? The rear head seems awful tight to access.
AnswerYes it can be done with the engine in the car.
The easiest way that I found to do it is to remove the pressure gage from your pressure tester long hose and put an air fitting on this end and remove the check valve from the bottom side of the hose that goes into the cylinder and this makes it simple to put air into the cylinders.
