1998.5 Cummins Diesel 2500 4x4.

Has anyone ever had to replace their temp sending unit or temp guage switch. Could one of these make my temp guage act erractic. Everything else has been changed; thermostat, water pump, fan clutch, flushed raditor, and replaced temp sensor, (the one right beside the thermostat housing.)

My guage still goes back and forth from 190 - 220.

I guess my question is; will the temp guage sensor make my guage act erratic.

Part Numbers: Sending Unit 50118052AA Temp Sensor: 4720314

Thanks

 

Anyone have any suggestions?

 

Does it do it at idle? only when warm? Please give more info.

 

Yes, it does it at idle and when driving. I let it idle for about an hour last night to watch the guage and still fluctuates more than I think it should.
It will idle at about 185 and then go to around 210 and then back down. It also does this when I'm driving. I can be at a stoplight and it will idle around 185-190, when I take off it goes to around 210 and then back down.

I flushed the radiator and had no heat. A friend of mine said I had air in the system. I tried to bleed the best I knew how and some heat returned. He said air in the system could cause the guage to act funny to. Have you ever heard of this, and if so what's the best way to to get all of the air out.

Thanks,
Chris

 

The first thing I would do is confirm that the coolant is actually making those fluctuations. Try to find some way to measure the temp to confirm. If you don't have access to an external probe, tape a thermometer to the upper hose and insulate it. If it holds pretty steady, suspect the gauge sender or getting air at the tip. I'm just an amatuer mechanic, but I'm stuck in a hotel room in N.J. and would like to help ifpossible.