Here the story.... I noticed that i had a rough idle when I was pulling a heavy load or when it would get up to operating temp. In the morning, smooth as can be. I also noticed a little foam in the radiator. I just pulled a trailer from arizona to florida, when i got to florida, my overflow was overflowing, and my radiator has nothing but fizz. No water in the oil, no vapor at the tailpipe, absolutely no blowby anywhere, just a rough idle and fizz. Sounds like a head gasket or a cracked head to me. Please, any suggestions would be great. also engine does not overheat. just a little when pulling hills with a trailer.... 220 degrees. Around town... fine. thanks yall in advance.:help:

Are you running 50/50 or higher antifreeze? Only reason I ask is that if you run all water you will get similair symptoms, if you do have antifreeze, then it pretty much means the heads got to come off.

do your rad hoses get hard pressureised instantly when engine is started cold? does it blow bubbles in the overflow when cold ?

nope it doesn't pressurize instantly nor does bubbles come in the overflow tank, but there are bubbles when idling in the radiator. I have more antifreeze than water in the system. thanks for the sugg. guys

Is your harmonic balancer ok?

It does sound like compression pressure is seeping into the coolant. If you let it idle with the cap off does the coolant start to rise after awhile?

PS mine does the same thing but I do run pure water. I'm just about ready to pull the heads and port,drill,paint and put headstuds.

Bubbles in the radiator when idling is almost always sign of failed head gasket(s);)