Originally Posted by bcomo
I wanted to add something about the purpose of a radiator cap.
The purpose of a radiator cap is to raise the boiling point of the water/antifreeze mix.
This is 100% correct. If one is concerned that the correct pressure cap will blow out the cooling system, it is time to perform a little service.
Additionally, the purpose of 7# caps was in the days of using either water or an alcohol based coolant. On this time period systems, it will not only cause spitting but will ingest air on the intake, creating air pockets and creating even more problems.
The AC radiator cap being correct for this period is interesting. I always cringed from anything not marked FOMOCO.