R0cketMan
Member
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.
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.