I have a 98 Jeep Wrangler v6 that loves to overpressurize the radiator cap during driving and it coats the under side of the hood with antifreeze. I have replace the rad cap with an 18psi cap and replaced the thermostat with a 109 degree thermostat with no result. I have flushed and filled and burped the system with no result. The system does not overheat and temp stay109 degrees. Any further ideas?
First off 109 degrees is way to cold. Typo, twice?
That would be correct. 190 instead of the 212 typical of the motor.
There is a possibility that you have a blown head gasket and that exhaust gasses are over pressurizing the cooling system. A blown head gasket does not always exhibit obvious symptoms so don’t count it out. The cooling system can easily be checked for the presence of exhaust gases at any shop.
That would make sense of the murky brown film on the rad cap. A blown head gasket would probably also allow slight amounts of oil into the antifreeze or vice versa right?
Absolutely. Is your oil milky looking? If so, don’t start the engine until the problem is fixed.