When I run my 93 prelude the pressure valve on the radiator cap opens and all the coolant eventually fills the overflow tank and then spills out causing the car to eventually over heat. I changed the cap thinking it might just be old but the problem still occurs. I know the themastat can cause the pressure to rise to high and cause the valve on the cap to give way but before I start changing parts I wanted to know what else can cause this and how I should go about trouble shooting it.

 

Have you recetly put a new headgasket on?

 

Like 20K miles ago

 

its either a blown headgasket or bad radiator cap

 

i would check your thermostat while you're at it, they aren't terribly expensive.