I have a 1998 Ford Taurus SE 6cyl 24 valve Duratec with about 135k miles on it. It has started to overheat. It has a closed system with the thermostat on the bottom passenger side. It isn’t leaking coolant but it does boil when it heats up and you can hear it whistle/pop around the overflow cap. I have drained the whole system using the petcock valve and have changed out the thermostat (which because of its location requires all the fluid to be changed or you get green rain). So, new thermostat, new coolant, still overheats. The defroster air is blowing cold. It has a belt driven water pump but I haven’t touched this. Both electric fans are working.
I don’t see anything in the oil. It is still a nice dark color, not milky or anything. I saw no oil in the coolant I drained. When it first starts, there is a few seconds of puffs of white/gray smoke but it is very light and goes away quickly. There is no water running out the tailpipes.
My question is, what is your guess on the cause? I’m at the point with the car, with its age and miles that I’m not willing to dump a lot of extra $$ into it – so there will be no head gasket change – but don’t want to junk it if its something simple. I do most of my own work on my cars.
Do you have any guess on the cause? How can I diagnose it further? Should I just change the water pump and if that doesn’t work then what? Or anything you can think of would be appreciated.