My 1988 5.0 F-150 (160,000 miles)will boil coolant out of my o/flow tank after I stop and turn off engine? I changed my thermostat, my rebuilt water pump is less than a year old, I put a new radiator in 3 years ago and I had my system flushed about a month ago. Also it only overflows when I run my ac which works fine.Anybody have any idea as to why it gurgles and runs out of my overflow bottle. The engine always runs with a good low range temperature, it has never overheated, even when I lose coolant. Any ideas?

 

head gasket is probably shot. Have someone put an exhaust/gas analyzer into the opening of the overflow tank and check the CO reading. If you get any reading at all it is a blown head gasket.

good luck-

 

Another way to check for a blown head gasket is when the motor is cold. Remove the rad cap and start the motor. If you see bubbles, it's a good sign you're blown.......

It could be that the cylinder pressure doesn't make it into the cooling system until after it warms up. If you find you can't even come close to opening the rad cap when it's hot, that's another sign. One thing to do is keep the cap off or just loose and let the motor reach full temp. Once the 'stat opens, give the motor some RPM's and watch the coolent flow. If it's really "froothy" looking, you're probably blown. Actually, if the later is the case, you 'could' have a cracked head.......

My wifes car did this and it was a cracked head........

 

Thanks hcmg & Mitch F-150, I really appreciate your prompt replies. Looks like a head gasket problem, from what you both have indicated. I'll bite the bullet $$$$, and have it checked ASAP.
Thanks again, Jim