I have trouble with my 91 Sport overheating in the summer. Replaced the tstat and housing. Would an 18 psi cap help my boiling point?

 

An 18 lb psi cap will increase the boiling point of a 16 lb psi cap by only 6*. Nothing is really gained by doing so. The radiator is the only cooling system component who's sole function is to dissipate heat. How old is your radiator? What other cooling system maintenance have u done?

 

Subscribing..will need cooling done soon

 

It will help to blow hoses, heater core, or radiator. Where ever the weakest point is.

Find and fix the problem. Don't try to band-aid it.

 

You have to provide a little more info like when idling, running 140 down the highway, stop & go traffic? Other than the thermostat any cooling system maintenance in the past 23 years?

 

THIS^^^^

Run the correct lb cap, and start tracing down the conditions when its happening.

 

16 pound cap works fine. But, it has to be functional. They don't last forever.