Low Coolent Level?

Ok first Hello to all you guys and I know there are some other coolent threads but I didnt want to jack their thread with my question so I thought I would start my own.

When I start my car my light is on (low coolent) but when it reaches temp the needle will drop and the light goes out. I checked my level in the radiator and it was full so and my reserve tank is at the full mark, also I tried to bleed the air out threw the thermostat screw on top. So im now kinda baffled and wanted to see if you guys think these symtoms sound familiar. Or if you have any ideas on what to check next? thanks ~joe

It sounds like the low coolant sensor is not making good contact and isn't reading correctly. You can pull it and clean it or replace it. The reason it is going off when the thermostat opens is due to the hot coolant. If the light isn't bothersome just leave it as is.

thanks alot GTPDAD..I thought maybe that too just because I replaced the t-stat and that was the last thing I could even remotly think of replacing..now, where is that sensor located? thanks again ~joe

I am pretty certain that it is located on the side of the radiator (passenger side). I don't have a book to give you the exact location.

Thanks alot, I found it. Ok I replaced it with a new one and started the car it was still on??? drove a bit and it went out, started car again and it was off. So i though it was fixed until i see it dimmly come on the 5 seconds later it dimmed off kinda faded off and on. Now im stumped, I checked fluid level put in a new thermostat, blead the air out through that nut on top of the thermo and now replaced this stupid sensor and Still this thing is comming on?? any other thoughts??

I too, share your frustration. I've replaced sensor, coolant, T-stat, and bled through T-stat housing on my '99 GTP. Light still come on, and usually goes off after 20 to 30 min. Radiator and revovery tank seems full and clean. This is quite annoying, huh?
Being an engineer, what really seems riduculous to me is that the sensor's "logic" is reverse; when you unplug the sensor, the light goes OFF.
I may try to clean the old sensor, and put that one back in. Just to see what happens.

I too, share your frustration. I've replaced sensor, coolant, T-stat, and bled through T-stat housing on my '99 GTP. Light still come on, and usually goes off after 20 to 30 min. Radiator and revovery tank seems full and clean. This is quite annoying, huh?
Being an engineer, what really seems riduculous to me is that the sensor's "logic" is reverse; when you unplug the sensor, the light goes OFF.
I may try to clean the old sensor, and put that one back in. Just to see what happens.


Isn't it wierd? I had the same problem last fall. I took my sensor out and cleaned it, and when I put it back in it worked great for two weeks. Then it came on constantly. By this time its starting to get cold outside, and I'm getting sick of staring at "Low Coolant" so I just unplugged it. Still is like that. Some time I will replace it, but I hope by replacing it, the problem gets solved.

Coincidently at the same time I started to have problems with my light, I had just gotten done changing my t-stat and coolant. I believe I still had dex-cool in it from the factory, and I replaced it with prestone dex-cool. Maybe prestone brand has a problem completing the circuit at the sensor? Worth looking into maybe.

Alot of us use the Prestone 5/150 extended life green anti-freeze (yellow bottle) and don't have level sensor issues so I don't know if that is the case although worth looking into. :dunno:

Try a conductivity test with a DMM on low dc volts scale. With ignition to off, meter negative probe to battery ground stud and dip the positive probe into the coolant the the filler neck. I believe the reading should be well below 1 volt. I get around .2-.3 volts.

So...that many people have moved off Dex-Cool? Interesting. What are some of the main reasons?
I've been running with Prestone's Dex-Cool. I changed coolant at 50k miles and at 100k miles. Both times coolant looked pristine, but I guess I'll consider the change-over.
I always thought (other than environmental reasons) that if/when ethylene glycol comes into contact with any fuel or products of combustion, highly corrosive compounds are formed; especially corrosive to aluminum. I thought this was the main reason for the switch to propylene glycol, no?
Anyway, thanks for the advice/info. I'll do the multi-meter check.

So...that many people have moved off Dex-Cool? Interesting. What are some of the main reasons?
I've been running with Prestone's Dex-Cool. I changed coolant at 50k miles and at 100k miles. Both times coolant looked pristine, but I guess I'll consider the change-over.
I always thought (other than environmental reasons) that if/when ethylene glycol comes into contact with any fuel or products of combustion, highly corrosive compounds are formed; especially corrosive to aluminum. I thought this was the main reason for the switch to propylene glycol, no?
Anyway, thanks for the advice/info. I'll do the multi-meter check.

I switched a few years back in my GTP because it was less expensive and easier to come by. Plus I replace coolant at tighter intervals like around 36K miles and always do a thorough flush. Not because I had any problems like sludge. However, I still run GM's Dex-cool in all my other GM cars.

Prestone claims the 5/150 extended life green does not damage any aluminum engine components or radiators but helps protect and from what I understand it is still OAT (Organic Acid Technology) based like Dex-cool. Now as far as GM's Dex-cool technically it is an ethylene glycol based product just without silicates and phosphates. It says so right on the front and back labels.

http://i5.photobucket.com/albums/y186/lizzywiz/DSC08894.jpg