My 88 5.0 keeps "overheating" according to the temp gauge. I've replaced the entire cooling system trying to hunt down the problem. (thermostat 4 times, radiator, hoses, fan clutch, guages, radiator cap.) Gauge will go into the red but car acts totally normal. It dosen't spew coolant, dosen't drive act or sound different at all. Any ideas?

 

check temp with a thermometer gun (sorry i don't know exactly what its called). this should show you if your gauge is working properly. so the gauge starts atcold and moves to hot?

 

INFRARED THERMOMETER
http://www.harborfreight.com/cpi/cta...emnumber=96451

I have heard of the head light switch causing false readings as well.

 

As always I'd recommend getting an aftermarket mechanical water temp gauge (& if possible a mech oil psi gauge), the stock gauges are pretty stupid. I know it says you checked the gauge, but what about the sending unit? Parts stores generally carry a mech water temp gauge with everything you need to hook it up for $15-20

Take your radiator cap off & turn the car on, rev it up, if coolant flies out you have a blown headgasket. This can cause the car to run alot hotter than normal, but drive like it normally does.
If it's not either of those then you probably have something clogging it somewhere.

 

the ivr may be bad in the instrument cluster I'd verify your overheat condition with a mechanical gauge or infared ray gun

 

try the sending unit

 

I've tried replacing the gauge with a mechanical one and nothing changed. I also changed the sending unit and checked it with an infared gun and the gun says the temp isn't changing. I forgot to mention that I also replaced the water pump. The car will warm up to normal operating temperature and stay there for a while (sometimes 2 minutes, sometimes 20 minutes) but then the gauge jumps up to the red and stays there anywhere from 10 to 60 seconds and then cool back down to normal. Thanks for your help!

 

sounds like an air bubble

 

MIne was doing the same dang thing and after replacing numerous parts, it ended up being a heater core, it leaked all over my passenger floor board, nowit runs as cool as Napoline Dynomite!