I have a 1997 Ford Explorer. About 3 weeks ago I took it in for an oil change and they found a leak on my water pump. After changing the pump, I drove to Arkansas on vacation (about 7 hours). During my vacation, on a short drive, my explorer overheated. We noticed a boiling sound and opened the hood. A little coolant spilled from the reservoir. The next day I took it to a shop and we couldn?t make it overheat. We drove back to Houston with no incident. This week it happened again, this time even more coolant came out. I took it back to the shop that did the water pump and they changed the thermostat. Then it happened again. This time I was across town and noticed the temperature gauge approaching the red. I turned off the AC and turned on the heater and the temp went down instantly. We stopped to pick up my son and while the SUV was idling, I turned the AC back on high and the temp did not come back up. We went on our way and the temp never got over normal. I?m perplexed.
Sounds like they never got all the air purged out of the system after the water punp repair. Some of these Fords have a pretty complex cooling system with coolant hoses going everywhere. Some don’t have a radiator cap, so purging out all the air can be difficult. By turning on the heater, maybe you “burped” yours. Check that reservoir tank daily when it’s cold and be sure it is staying full…
If you have a pressure cap, replace it. You are losing pressure, or else there is air in the system creating too much pressure and foaming. The route you describe has been unreasonably hot over the past month, and I guess the A/C had been on full time.
It was a good move to turn off the A/C and turn on the heat when the engine overheated. By turning on the heater, nothing was burped but you gave the engine another method to lose heat. It was enough to get you where you were going. Maybe this vehicle just cannot handle 120 F heat with the A/C blasting.