Running Hot

[BamaHeel]

So I got my oil changed at the dealer yesterday 137,000 no issue of note to date. Have had no issue leaving. Drive around rest of day problem free.

Today drive about 15 highway miles to destination, stay for an hour and on return trip AC goes Luke warm, look at temp gauge on interstate and just below red.

Slow from 75 mph to 60mph and temp starts dropping with rpm's.

Approach a hill with a steady, slow, uphill climb and temp shoots up to red.

First thing I checked was the radiator and overfill level and I'm good.

Get home, search, and after conferring with Bamachem decide it's the fan clutch which spins freely. Get a new one, install; try same hill after new fan clutch installed and temp shoots up. AC heats up.

I haven't puked fluid so mechanical water pump working so only thing left is thermostat, correct?

Any other ideas?

 

[Sandroad]

If the fan clutch and water pump are working and the coolant level is ok, I'd agree with new thermostat next.

 

[TXLX100]

I'm a big fan of preventative maintenance thermostat replacement. Seems like when it goes bad, it usually blows up the radiator.

 

[scottryana]

Radiator is going bad. Usually the sign when can't cool at speed.

 

[TeCKis300]

I would not suspect the fan/fan related parts if it's overheating at speed. The fan only really comes in at idle/low speeds.

If you're not losing coolant...

Thermostat would be a good one to check.

Have you been mudding lately? It's possible your radiator is gunked up and unable to shed heat.

 

[BamaHeel]

I haven't been in the mud in a while. I'm doubting thermostat because the fluid in the radiator is very hot. I thought bad thermostat equals hot engine and cold radiator?

Is it possible for the water pump to fail with no outward signs of failure? I. E. Not puking fluid?

Not sure.

 

[BamaHeel]

New idea on thermostat. What if it's stuck open instead of closed and not slowing water down to cool off so it's just circulating hot water?

 

[SWUtah]

Only thing left is thermostat. I would also put on a new radiator cap and over flow cap.

 

[BamaHeel]

New thermostat installed and back to normal. Drove around for a while with ac on COLD on interstate and up and down hills never got above mid way on temp.

Thanks to everyone for their input.

 

[TXLX100]

I haven't been in the mud in a while. I'm doubting thermostat because the fluid in the radiator is very hot. I thought bad thermostat equals hot engine and cold radiator?

Is it possible for the water pump to fail with no outward signs of failure? I. E. Not puking fluid?

Not sure.

Glad you got it fixed. Nearly ever catastrophic radiator failure I've seen on a 100 was due to a failed thermostat. So it would have to build some heat and pressure somehow. I'm guessing it stays closed stopping the coolant flow causing engine temps to rise and heat and pressure to build up in the radiator.

 

[SWUtah]

Stuck open is not a problem other then it takes longer for it to heat up. Only one or to members with bad thermostats on the 100 forum.

 

[looking4lc]

planning to replace thero as preventative maintenance, middle east is twice hotter than US