Engine temp needle works fine at idle but jumps around like crazy when I tap on the accelerator. Started after I drained and refilled the antifreeze to fiz a leak. Help!


gdenham@copper.net

 

Most likely you have air in the system. If you have a 6.5TD, there is a bleeder on top of the thermostat housing if I remember correctly. Im in Afghanistan right now and haven't seen my Hummer in 5 months. But to get the air out of the system, this is what I do.
- Ensure your coolant reservoir is up to the full line.
- Start the truck and let it warm up.
- Carefully loosen the bolt that is on the top of the thermostat housing you should either get coolant or air coming out. Do not take the plug all the way out. Only loosen it until you have fluid running out or air hissing.
- once your satisfied that most of the air is out of the system, tighten the plug back up.
- You may have to do this several times to ensure that all the air is out. When I did mine, I got a good bit of air out just by letting it warm up at idle. I took it for about a 15 min drive and watched the temp gauge closely to see if it acted funny. It danced just a tiny bit so I did it again. Havent had any issues since.
- Another possibility is a bad sending unit, but I highly doubt that if it worked fine before you drained the coolant

 

I haven't had a chance to try that yet, but I will let you know how it works. Thanks for your service, be careful over there.