2005 Pontiac Vibe wagon...over 300,000 no issues until recently. The temp gauge goes to overheat. Here is what has been done in the past two weeks. New thermostat, proper coolant, new radiator cap, sensor, and just installed a used gauge panel. Fan is plugged in....heat sensor gun shows normal temps. Help! I'm a single gal who doesn't want to be taken advantage of...any ideas? Thank you!

  • This could be as simple as a bad electrical connection between the temp sensor and the rest of the electrical system. Try unplugging the cable from the sensor. Does the gauge immediately rise to "hot" even when the engine is completely cold? If so, you still have to track down the problem, but you know what you are looking for! Note, the problem might not be at the temp sensor end of the wiring - it could be another connector, or a damaged wire.
    – alephzero
    Commented Jul 2, 2017 at 0:49
  • Connect a OBD2 scanner and see that the computer temp sensor (ECT) says.
    – Moab
    Commented Jul 2, 2017 at 1:30

4 Answers 4


I would make certain that the system is bled properly. A small air pocket around the sensor can have really erratic effects on the "gauge" temperature.

Especially if the sensor is in the very top of a housing, where air may accumulate. Some thermostat housings have a small bleed screw to make this easier.

In general, park the car on a slope such that the front wheels are slightly higher than the rear (driving "uphill').

Remove the radiator cap and leave it off. Set the HVAC temperature to full hot, with a middle fan speed.

Start the vehicle and fill the radiator with the proper coolant mix. Idle the vehicle for a length of time... this could be as much as 30 minutes or more with some vehicles.

Observe the coolant in the neck of the radiator fill. If there are small bubbles bursting, it isn't bled yet. Keep adding coolant mix to keep all radiator fins covered - just below the filler neck.

When the bubbles stop, cap the radiator BEFORE you turn the vehicle off.

Then you can observe your temperature gauge and see if the response has improved. It's a simple process that may not solve your problem, but can't hurt. A properly bled cooling system is essential and a bit of a lost art with some mechanics - especially because it's time consuming and doesn't make them any extra money really.

Good luck!


Change the temp sensor. You pretty much changed everything else already. Also you may want to find another mechanic.

  • Sorry...we did that to...I just looked at the receipt....any chance it's the pump? Commented Jun 30, 2017 at 22:26
  • If it's NOT overheating its not the pump. It's an electrical concern. Something between the gauge and where the signal comes from. Signal can go to the pm then to the gauge, it may go to a body module then to the gauge. Your mechanic needs to find this out and go from there. Hope this helps
    – cano
    Commented Jun 30, 2017 at 22:54
  • What is the pm? A friend of mine said something about a "sendor" to the coolant gauge??? By the way, I do really appreciate the help! At this point, is it worth going to a dealership for a diagnostic? Find out what it is and have my mechanic fix the issue as dealerships are expensive. Thank you again.. Commented Jul 1, 2017 at 14:21
  • Sorry, typo. It should have said pcm. Power train control module. How it works is. Assuming the cooling system is operating normal. The sender/temp sensor will send a signal to either the instrument cluster/temp gauge or to a module like a pcm/or another module then to the gauge. Your call if it worth going to a dealer.
    – cano
    Commented Jul 1, 2017 at 14:33

It's the radiator itself. I went through this with a Ford years ago . It kept overheating and I changed EVERYTHING. Except the radiator. Open the cap and shine flash light into the rsfiatpr. Is there anything that looks like calcium growing I in there, like coral almost ? That build up does not allow the heat to disperse as the water flows throw the radiator. What t o do? If you can ,take it out and break up the deposits inside by hitting the corner of the radiator on the ground. I ve seen that done in a shop. Or just get a new one..

  • If this was the case, wouldn't the heat gun show the engine over heating?
    – wesanyer
    Commented Oct 11, 2018 at 13:20
  • Welcome to Motor Vehicle Maintenance & Repair! :o) Commented Oct 11, 2018 at 17:34

Temp sender unit is faulty: Remove the sender unit wire and earth it against the bodywork and the gauge should go straight up to hot. This indicates that the gauge and wiring is fine and that the sender unit is faulty.

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