Temperature - one more time

[bobweiser]

So I've done a search on thermostats and cooling issue and :eek:

Sounds like one of the biggest gremlins in these trucks.

 

Anyways, '89 MJ 4.0l, had been sitting for a few years, but back in action now. I installed the guages over idiot lights and replaced the sensors. Quick drive over to the gas station, the guage went to the red line after a few minutes. Same on the way home. Didn't boil over and my cheapy laser thermometer only showed 175 max at the plastic tank. I could grap the radiator hoses with my hands, hot and flowing.

 

Is it still worth a new thermostat or are these guages that bad?

If a thermostat, which one?

Thanks guys.

[BLHTAZ]

From your description...it sounds like yours is just a guage issue. I would make sure that your laser is accurate and check temps on the head, block & t-stat housing just to be sure.

[bobweiser]

Thanks Brent. That's my thought. I am going to borrow a good IR gun from the paper mill and double check everything.

 

How much is a new guage? Also if I do buy a thermostat, parts store ones ok or does it need to be an OEM?

[BLHTAZ]

Guage would cost you $50 shipped.

 

The t-stat is OK from aftermarket as long as it has the little pass through hole in it with the check ball that goes in the 12:00 position...otherwise get OE.

[500 MJ]

Lol, my "operating temp" is around 130...

 

I just use the gauge to tell me when things aren't normal...

[Eagle]

I think the OP has air in the system. If there's air, the coolant won't flow to the surge tank, and the temp sensor for the gauge will read hot because it's at one of the hottest points on the engine (which is why they put it there) and tends to attract steam pockets if the system isn't full.

 

Another cute trick is, when the system isn't properly filled there won't be any heat, because the coolant level is too low to flow through the heater core.