Diagnosing Overtemp....Culprit Found?.......

[nosliw]

Looks like my temp gauge is grossly inaccurate.

I installed a cheap-o Summit Racing mechanical gauge along side of the factory sending unit, and wedged it in the dash between the front axle switch and the heater controls.

The OE unit is reading 200 degrees, while the Summit one reads around 160.

I installed a new thermostat just as a safe measure, but really dont think it would have made a difference, once I opened the box and looked at the new thermostat. It look like a "coolant resistor". I really don't see how, mechanically, this thing would or could open and close.

In the process of looking at the wiring for the temp gauge, I managed to short out the entire electrical system, melting what looks to be a fusible link between the main wiring harness and the alternator, right at the alternator itself...No start, no fuel pump, no gauges, no nothing.

Figured that out and now the deuce is outside idling, I'll post back up when I return from hauling water to say "yea" or "nay" on my overtemp diagnosis.

Thanks to SteelSoldiers for once again, saving the day with wiring diagrams, and other information.

 

[taylordc15]

I was having overheating problems, and put a new thermostat in, after trying everything else it ended up being the thermostat. The new one I bought was packaged wrong, it opened at a higher temp than advertised. I had even pulled it and tested it but I didn't have a thermometer so I saw it worked and assumed it was good but it was opening at the wrong temp.

 

[Jake0147]

The thermostat does not fully open and fully close as you are thinking of, but it does direct 100 percent of the coolant flow through the radiator when it's "open" and directs 100 percent of the coolant flow to bypass the radiator when it's "closed", or any balance in between the two. There is always 100 percent coolant flow within the engine it's self so that hot spots do not develop when minimal or no radiator cooling is desired. I studied that for a bit before it hit me. You really have to look at the housing too, the thermostat by it's self does not tell the whole story.

If your gauge is outta whack, it's pretty simple. Power to the gauge, through the gauge, out to the sender, and the sender is a variable resistance to ground. When the summit gauge says 180 (straight up on your factory gauge) plug the factory gauge wire into another electric gauge. (Fuel level, oil level... I'm not sure about the volt gauge). The scales are printed differently, but the needle should still point straight upwards. If this test makes the needle on your test gauge point the correct direction, (again, don't read the scale), then the sender is good. If the test gauge points the same direction as the factory gauge did, then I'd suspect the sender.

 

[nosliw]

made a good trip hauling water with no overtemp issues. (but now have electrical problems) the stock gauge read 220 and the summit never got above 170. I've got a pretty big military surplus place right down the street and he may have a sending unit. if it's cheap enough, i'm going to go ahead and replace it and see if the factory gauge lines itself out.