89 E-150 300 straight 6, C-6 automatic, overheating problem. Bought the rig about two years ago and it has always run borderline hot - usually noticeable in hot weather. Changed out thermostat (185 vice specified 195 degree), waterpump, temp sending unit and fan clutch about 6 months ago. It seemed to fix the problem for while. Then it popped back up. Changed out radiator and two more thermostats... but the evil pig still over heated in 10(f) degree weather. Flushed the entire cooling system when replaced the radiator and am running proper 60/40 coolant/water mixture.

Pulled thermostat and she runs okay but obviously cold. without thermostat, I can get it to warm up by placing cardboard over radiator.

I figure one (or more) of the parts I replaced is bad: fan clutch or water pump. Any ideas?

By the way, it over heats quicker when the heater is turned on.

Supplementary info: oil pressure gage goes higher as temp increases. Oil gage reaches max before temp gage leaves normal range. I believe this is a coincidental shorting problem, but it may be related. I dont believe the oil pressure is changing that drastically, but just this evening I put a direct pressure gage on it and will run it on the highway in the morning.

 

YOu will probably need to drill a small hole in the thermostat so that water/coolant will circulate through the system when you first start it. Drill it in the bottom if the thermostat. Also check your heater core as it could be forming a block.

 

The Oil pressure going up and temp going up is unusual.. If anything the oil pressure should go down as the engine temp heats up...

I know on my 91 when I run the heat the temp gauge does go a little high but, it never boils over.

if it doesnt boil over then i wouldnt worry about it these thin wall engines will run close to 220.

 

Are you reading this on a factory gauge or on an aftermarket one? Mine turned out the factory gauge was reading alot higher then the actual temp. was.

 

There is no calibration to the stock gauges, some read hotter, some colder. As long as it's not in the red you are fine. When it shows hot, feel the radiator and the hoses connected to it. They should be hot, if the top hose is just warm check the bottom as the thermostat may be stuck shut.