Oldsmobile/Buick Repair: oldsmobile radiator cap, 1995 oldsmobile ciera, oldsmobile ciera

Question
I have a 1995 Oldsmobile Ciera with a 3.1 L V6. The car has recently been experiencing overheating problems. There are no leaks, the thermostat is OK as is the water pump. The issue I can see is the radiator cap does not seal off the overflow bottle. Squeezing on the upper or lower radiator hose causes the level in the bottle to bounce even when the engine is cold. The same problems exist even after putting on 2 seperate new radiator caps.  

Answer
Hello David,
Along with the radiator cap, there are two sealing surfaces for it.
One is the top lip of the neck, which seals against the gasket under the top edge of the cap.
The other is the little ledge down inside that top part of the neck. The gasket on the bottom surface of the cap is supposed to seal there.
Possibly it is bent.

At any rate, just the fact that coolant is free to circulate to the coolant recovery tank, shouldn't cause overheating.
it should actually run normal with the complete bottom check valve removed from the cap, it just wouldn't be under pressure, so severe service would cause overheating sooner.

If it is really running hot, make sure the fan is coming on.

And check that neck area.

Van