Blown head gasket. With respect to the other responders, with the symptoms you have It is not a pressure test you want but a 'Combustion Gas Test'. This is a chemical test and very quick and cheap, it detects combustion gases' in the cooling system. If the test is positive the head gasket is blowing, if it is negative then it is a different fault, maybe stuck thermostat or failed water pump. With a compression test there is always some risk of damaging the radiator particularly if it is an old one.
Hi first thing is to buy a new radiator cap as over time the spring becomes weak.
If the 15 PSI cap is blowing, it's time for a cooling system pressure test to see if you have a blown head gasket.
Basically, if the cylinder compression pressure is breaching the head gasket into the cooling jacket it will pop the cooling system pressure cap.
change your thermostat most diffidently first. Check you hoses and make sure none of them have collapsed. A blown head gasket will make your car blow out a lot of white smoke and idle erratically. The process of elimination when working on anything is to start with the most simplest , cheapest and most often main cause of trouble shooting . It will save you a lot of money in the long run.
Needs a pressure test done on the cooling system, could be the head gasket, could be something else. Any garage can do the job.
Thermostat is stuck in "closed" position.
Blown head gasket
BLOWN HEADGASKET
sprinter 2005
