I agree that some pressure in the cooling system is a good thing. I have no idea what the original system called for, and since this car has the B20 engine and a mis-matched radiator, it will take some figuring to come up with a cap that hold the right pressure for this particular system.

The PO's problem was that she was using a 15-lb. cap and was blowing out new radiators and heater cores. Going with no system pressure cured that problem, but of course the cooling system is no longer as efficient as it could be.

The big overflow tank keeps me from losing coolant onto the road, but it may become passé with a correct thermostat and radiator cap.

Luckily, I don't have to depend on the car for transportation, so I have the opportunity to take things apart for several days at a time.

Lately, even in summer heat, the car is running in the middle of the heat gauge. I probably won't fiddle with the cooling system very much until I have finished up some more pressing jobs.