If you added coolant, how much? If it hasn't overheated, then the theory of a stuck closed thermostat is not necessarily fact. If it was low on coolant, and you pressure test it and find no external leaks, monitor it and if it gets low again, it may be going internal. A few common places for leaks are the water pump, water pump cover, water pump housing(aka crossover), hose connections, the radiators can leak as well. If it has a black(phenolic) water pump cover, that has been updated to an aluminum one, because of the possibility of leaks. But like I say, I would not spend a bunch of money trying to fix coolant loss without having it block tested. Head gaskets, or more specifically the head bolt threads that degrade, are real common problems on a Northstar. To have that repaired professionally, it can run in the neighborhood of $3000.
Saturday, June 26th, 2010 AT 5:25 PM