2000 GMC Jimmy Temperature Gauge Reads 1000
 

Ok, it would read 1000+ if the dial was numbered that high.

Stuck in traffic the temp gauge headed to right....service engine, check gauges light illuminate. I head for the freeway exit at 10mph and temp heads down a bit but too high. I pull off and find no coolant in the reservoir. I foolishly didn't check the coolant level (6 months) after a new radiator was installed. No leaks noted.

I added coolant and the temp was still elevated but if I kept moving, no problem (never moved over the half way point). This morning I started the vehicle and let it run (parked) with no problems, no lights. I replaced the battery I had purchased last week. Then I noticed the temp needle buried to the right (what would be 1000+ degrees). Other gauges are fine.

Any idea what may be wrong?

Possibly the water pump is failing. There is a weep hole on the bottom of the pump if it looks like there fluid coming out the hole then pump going bad.

If the coolant temperature sensor, or the wiring, has an open circuit, the needle will peg past full hot. Might be the connector came off, or the sensor went bad.

It sounds like you have a coolant leak as well, leaky lower intake manifold gaskets are a very common problem on 4.3's. A cooling system pressure check will locate the leak.

Thanks Bowtie and Cap Hook.
I drove the Jimmy for about 10 minutes and the temp gauge returned to normal. I've run it down the highway, stopped while it was hot and no problem.
Looks like I need to followup on the leak.
Thanks for the help.
Doug
Native Michigander

Lower intake gaskets can and do leak. Many times they leak onto the hot exhaust manifold or cylinder head at the rear of the engine. When this happens, the coolant instantly vaporizes so you may or may not see signs of a leak.... maybe a little white or orange residue, but that's about it.

Thanks Captain!