I searched but I could not find what I was looking for. I just installed a rebuilt 5.0 into a '91 Mustang and it's overheating. The water pump, radiator and thermostat are brand spankin' new and coolant is not leaking from anywhere. There does not appear to be any air in the system although there is the occasional bubble in the overflow tank.
There is a slight chance that the heater core hoses were installed in the reverse order, although I don't think that would cause overheating. The temperature dropped when the heater was switched on, but eventually overheated again. I was thinking that the heater core might be plugged but the hoses to it were pressurized. Otherwise I am stumped. Any help would be greatly appreciated.
I am relying on the factory gauge, but the engine is ticking like it's hot. It's not boiling over, although it was overflowing out the spout on the overflow until I replaced the (brand new) thermostat with a brand new thermostat. The newest t-stat made the overflow stop boiling (as if there was still air in the system), but did not quite correct the problem.
Before the t-stat replacement it was running cool at idle in park, but would overheat while moving (which is very backwards). I could get it to cool down on the move by putting it in neutral and revving up the engine or accelerating in gear.
And the fan is installed correctly (one of the threads I found said that people sometimes install it backwards).
if it isn't boiling over, you probably really need to confirm what your temperature gauge is telling you.
Factory guages are not reknown for thier accuracy, then you add a few years of wear on them......
A decent electronic thermometer or even guage would give you a better picture of whether you really have a problem or not.
We checked the head gasket, it is in correctly. We also torqued it on according to the Haynes book. I'm thinking it might be a clogged radiator, even though it's a new radiator. Thanks for the help guys.
Well, we figured it out. The head gaskets were cheap ones that allowed the exhaust to leak into the coolant. Then the heads got overheated and warped .004" which required a resurfacing job to fix them. Hopefully this might help someone in the future.
If only we had used FelPro gaskets from the start we wouldn't have had to waste so much time.
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