1997 ford f-150 overheating

I have a 97 f-150 with a 4.6 engine 4x4, just recently i have been having intermittent problems with it overheating. I will be driving along the temp. gauge will read normal, than out of nowhere the needle will spike all the way up to the red and the overflow will bubble over. I can stop the truck and turn it off and turn it back on and the needle will read normal and everything will be fine. I had the mechanic flush the system, install a new water pump tstat and even added blue devil head gasket sealer. It didnt seem to work because I drove it for 8 miles and it did it again but drove it the same distance three more times with no problem. Could it be as simple as needing a new radiator cap?

It is possible it is a radiator cap. Try it and see.

The cap can cause the loss of coolant which will cause overheating but as long as the system has sufficient coolant and no air pockets develop a faulty cap will not cause overheating. But as cheap as a cap is I just replace them whenever there is an overheating problem because caps often fail soon after some other problem caused overheating and is corrected.

Is your coolant tank pressurized and it fact there is no radiator cap, just a special cap that seals the recovery tank? In a Crown Vic, these engines have some pretty strange plumbing…

While a blown head gasket is very rare in these engines, it’s possible and it matches your symptoms…'Blue devil" will not repair a blown head gasket. A simple sniffer test will confirm a blown gasket or rule it out…

I’m having the same problem w/my '97 4.6.Wouldn’t there be water in the oil if the head gasket was blown? Someone told me that a piece of gasket material from the heater core my be floating around and intermittently lodging in the system. Could that be it? Also, what is a sniffer test?