Hi,

I have a 4.9L 6 in a 92 F150. I posted a couple weeks back about a possible cracked head or blown head gasket. My only symptom is the engine overheats very quickly. I am not getting white smoke out the tailpipe nor am I losing coolant under pressure out a crack in the engine compartment. I've been told that means exhaust gases are getting in the coolant and there would be bubbling in the coolant in the overflow. I checked and I am not getting any bubbling there. All I found was a thin film of white foam at the radiator cap. I removed the spark plugs one at a time and checked the coolant each time. There was no change. Any idea what is causing this? My thermostat and water pump are fine.
Thanks

 

You might also check for a clogged radiator preventing adequate water flow, a faulty fan clutch, and/or a restriction in air flow across the radiator fins. I have had debris build up between the radiator and the condenser coil shutting off the air flow.

 

I agree that I would flush the cooling system. I have seen many clogged radiators cause this exact problem.


I assume that when you say that both the thermostat and pump are good then you have either tested or replaced them?

 

The water pump having to be replaced is what started the whole mess for me. My sepentine belt broke while I was on the freeway. By the time I noticed the temperature spiking, I had driven 5 or 10 miles. The pump was trashed so I replaced it. It is still overheating very quickly. I took the thermostat out with the same result. A buddy of mine who is a mechanic is sure the head gasket blew or the head has a small crack. I want to try a sealant before I remove the head, but I've been told that they won't work if the crack is near any of the pistons

 

Personally I would flush the radiator a couple of times using a quality coolant flush before I would do anything else to it. If you do happen to use a sealant then I would bypass the heater core so you don't risk stopping it up in the process.