2000 GTP coolant level sensor problem.....

Hey guys, 2000 Grand Prix GTP, supercharged 3800 V6, 80,000 Miles (no mods.....Yet). About a week ago as preventative maintanance before winter i changed my thermostat. To do this, I drained all the coolant in my radiator by opening the petcock. Once the change was done I filled it with coolant and bled it from air. Seemed ok, no overheating. So a few days ago, leaving my job, my low coolant light came on. Thinking it was just low from a little air left in it, i pulled into the gas station, turned it off, grabbed my dex cool 50/50 mix from the trunk, popped the hood and took the radiator cap off. It was completly full. Thinking maybe the sensor was in the overflow, i popped that cap off and noticed it was alsoa little above the cold mark. Since my car was cold, i figured this was ok. Got back in the car, started it up, light was still lit. So it was late (11pm) and since it wasnt a hard fault, i decided to drive it home. Once back on the highway about a mile, the light went off. And stayed off the whole way home. (Fixed it.... Yeah right)

Next day about 9am got in my car to go mail some bills. Started it up, light was on. Turned it off, checked coolant, it was full. Halfway up to the post office it shut off. What the f&$k? Its happening more frequent now to the point i dont even check my coolant level. It also seems to be only happening when the car is first cold started when the temp is below 70 degrees, and seems to stay on untill the car warms up to operating temperature.

My question's.

---Is this sensor just simply a thermister that varies resistance with temperature? Because thats almost what it seems like to me, but that doesnt make sense to use as a level sensor.

---Where is this sensor located? Maybe did i possably bump something reaching the petcock from the top of the radiator?

---What should i do? Its getting quite annoying and now that the temp here is getting lower at night it seems to stay on longer when i leave from work. I would like it to work just fro piece of mind. Any ideas?

THANK YOU!!!!!!!!!!!!!!1

Possibility you may still have air in the system or maybe the sensor is just acting up. Try bleeding again or you can remove the sensor and clean it out as a first step. Located on the right hand side of the radiator about 3 inches below the filler neck.

http://i5.photobucket.com/albums/y186/lizzywiz/coolantsensor.jpg

Great thank you. I will try that!!!!!!!!!11

Today I had to cut the grass and go straigt to work after. But i did have a few minutes to mess with the sensor. This morning i checked the level in the radiator. Full. Started it. Low Coolant light was on. I shut it off, and unplugged the sensor. When i started it the light was off. I then jumpered the terminals of the connector with a paperclip and started it again. The light was now lit. This tells me that the wiring and PCM is doing its job correctly. I guess maybe tomorrow before work i will take the sonsor out and clean it up, maybe its just dirty or maybe its bad. Tonight the light stayed on the whole way home. Its getting evry annoying.

One more quick question... how does this sensor come off. It appears the battery has to be taken out. I dont see any bolts or screws. Thanks!!!!!!!!!

That is correct Tblake. Battery should be removed since it is in the way. The sensor retainer is a clip.

Ok, this morning i got out to my car and started it. "Low Coolant" was lit. Pulled it up to the garage and removed the sensor. It was full of some brown gunk. So i just cleaned it up and put it back in. When i refilled the radiator and started the car, the light wasnt on. Nor did it come on when i left for work tonight. It looks like problem solved. Thanks so much or the help bnaylor

Did you have to remove the battery to remove the sensor? I was replacing my passenger-side side-marker bulb this weekend and while the headlamp assembly was out, I thought that I have full access to the coolant level sensor (and as well as the horns). I don't know if it is easier this way and not having to remove the battery.

BTW, my coolant level light has been staying on for like 5-20 seconds longer than other lights after my car is started the past weeks. I think my coolant level sensor is due for cleaning.

I never thought of that. I'm sure it would have been easier to remover two bolts instead of the rad overflow, fuse box, and then battery. Might be worth a shot. Wish I'd have thought of that.

The coolant level sensor is on the backside of the radiator tank, between the radiator and battery, so removing the headlamp wouldn't help.

I agree there is only about two inches clearance to get the sensor out so IMO battery removal is still the best route. Also, easier to get to the level sensor electrical connector located underneath. Doesn't take that long anyways.

00' GP SE
Miles: 120+Km

Question: How can I check my coolant level?
How can I check to see if it is good?
If my temp. gauge is not reading on my dash, how can I fix the problem? Is it the coolant temp. sensor? or something else?

Any advice would be helpful!


I agree there is only about two inches clearance to get the sensor out so IMO battery removal is still the best route. Also, easier to get to the level sensor electrical connector located underneath. Doesn't take that long anyways.

Question: How can I check my coolant level?
You can check your coolant level when the car is cool by taking off the radiator cap and seeing if the coolant is right up to the neck (checking the reservoir level is not very accurate).
How can I check to see if it is good?
There are commercial test strips that you can buy ($3-$4 for a vial of 25) that will test the acidity of the coolant.

If my temp. gauge is not reading on my dash, how can I fix the problem? Is it the coolant temp. sensor? or something else?
The temp guage is controlled by the PCM (Powertrian Control Module) via the CTS (Coolant Temp Sensor). Normally, if the CTS is bad, it will also trip a check engine light, so there may be a problem with the wiring between the PCM and the cluster.

Indeed, the check engine light is not on, but how can I locate the PCM to check the wiring?

You can check your coolant level when the car is cool by taking off the radiator cap and seeing if the coolant is right up to the neck (checking the reservoir level is not very accurate).

There are commercial test strips that you can buy ($3-$4 for a vial of 25) that will test the acidity of the coolant.


The temp guage is controlled by the PCM (Powertrian Control Module) via the CTS (Coolant Temp Sensor). Normally, if the CTS is bad, it will also trip a check engine light, so there may be a problem with the wiring between the PCM and the cluster.

Are you indicating I need to locate this particular part and remove it then clean it and after reinstall it?


Possibility you may still have air in the system or maybe the sensor is just acting up. Try bleeding again or you can remove the sensor and clean it out as a first step. Located on the right hand side of the radiator about 3 inches below the filler neck.

http://i5.photobucket.com/albums/y186/lizzywiz/coolantsensor.jpg

Are you indicating I need to locate this particular part and remove it then clean it and after reinstall it?

Only if you are experiencing coolant level indicator problems or if applicable to your problem.

I agree there is only about two inches clearance to get the sensor out so IMO battery removal is still the best route. Also, easier to get to the level sensor electrical connector located underneath. Doesn't take that long anyways.

FYI, I am not sure how much a difference between my 2001 GT vs the GTP or any other model year. I removed and cleaned my coolant level sensor by pulling the headlamp only. Pretty easy and only tool I used is a narrow screwdriver to pop the metal wire-retainer... I also replaced my lower coolant hose which turned out a lot more difficult as I was unable to remove "GM hose clamp".

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