Does anybody know a "rule of thumb" for realistic cooling system leak rates on 300-ish CI v8 engines?
Tested with compressed air, the cooling system drops about a quarter PSI per minute at 9 PSI. There's an audible leak at the water pump shaft, which changes when the shaft is turned. Bearings feel good, no noise, bind or play.
The longer story is that the car very slowly lost coolant through visible weeps in the (20 year old!) radiator. I did a final pressure test before pulling the radiator, finding no leaks except the radiator and an insignificant leakdown rate, convincing me that radiator was the only problem. A bench test confirmed the repaired radiator is tight
Now that it's back together, a final (air, not coolant-filled) system test shows what seems like a larger leak. Cooling systems are far from perfect, but several PSI per hour seems like a lot. The Stant pressure test instructions suggest a "steady" reading for two minutes is acceptable, but that is with coolant, not air.
Thanks for reading, and any thoughts....
bob prohaska
Anybody been through this sort of drill?