Not wanting it to be a head gasket

[R0cketMan]

I had an old 1991 Ford Explorer with a 4.0l v6. It ran well for a while then the temperatures started creeping up. It eventually got so bad, I could drive maybe 10 minutes or so before having to "burp" the coolant system by opening the radiator cap, and quickly, before the temperature pegged the gauge. Other than this extreme condition which caused me to put the vehicle down for service, the vehicle operated a bit warmer, but it was never a problem. The expedition has a surge bottle with a pressure release cap that could be releasing gasses being built up from localized boiling, etc.

Long story short, the shop found BOTH heads were cracked in the exhaust ports of the cylinders closest to the firewall. There was no oil in the coolant or vice versa, and no carbon in the coolant at this time either, just the exhaust gasses creating air pockets in the coolant system. If you suspect ANYTHING wrong and the repair requires the cylinder head to be removed, have the cylinder head "Magna-fluxed", or checked for cracks. Had I not asked the mechanic to do this with my Explorer, I would have paid him for replacing gaskets unnecessarily while the issue remained unfixed.

 

[tekrsq]

Long story short, the shop found BOTH heads were cracked in the exhaust ports of the cylinders closest to the firewall. There was no oil in the coolant or vice versa, and no carbon in the coolant at this time either, just the exhaust gasses creating air pockets in the coolant system. If you suspect ANYTHING wrong and the repair requires the cylinder head to be removed, have the cylinder head "Magna-fluxed", or checked for cracks. Had I not asked the mechanic to do this with my Explorer, I would have paid him for replacing gaskets unnecessarily while the issue remained unfixed.

Yeah, honestly, I'm learning more towards cracked heads than a cracked head gasket. Anytime a head comes off my vehicles, it gets magna fluxed and x-rayed. It's stupid not to.

 

[tekrsq]

Try running the truck at load (the point where you see higher temps) with both the front and rear heat set on on high temp and high fan and all windows open. This will essentially expand the size of your radiator. First take note if the both heaters are putting out very hot air, indicating good coolant flow and then if this helps control the engine temp. If you get a lot of hot air and it lowers engine temp, it would indicate not enough enough coolant flow moving through the primary flow circuit. If you don't get very hot air, that would indicate not enough coolant moving through the system at all.

Besides a cooling system pressure test, you can also do a static compression and leak down test to get a better feel for the status of the head gasket, head and block.

Tried playing with the heater this weekend. Heat was normal, and didn't see any changes in engine temp one way or the other.