I am having an issue with an 06 4.0. So far no external coolant leaks, oil level not growing car does not steam out of exhaust. If you fill the coolant car run smooth, cool no issues, occasional whiff of antifreeze. The last trip was 2 hours all ok didn't heat up,then when the car was turned off thecoolant blew past theradiator cap out onto the ground. I have replaced the rediator cap just a cheap easy start didn't help. I don't have a radiator pressure tester and no access to one yet.

Thank you, Paul

 

tstat? waterpump leaking? whats the oil look like? whats the coolant look like?

 

There are no external leaks.The oil is clean and clear no bubbles, etc.
the coolant is clear no mixed fluids etc.I don't think the tstat is bad, but it hasn't been replaced yet. The car doesn't warm up fast or get hot like a stuck thermostat.

 

some tstats will get stuck in the open position to prevent the vehcile from overheating