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Low coolant light

2002 montecarlo ss 3.8low coolant light came on the last few days.and went checked the hose from the radiator to resivor no coolant came out.added some coolant light went out.marked the coolant level.staying on the mark.if i am leaking coolant into the engine were would it external leaks.even with the coolant in the resivor the light still comes on and goes out.even with the coolant in the radiator and resivor.what can i do to see what the problem is.dominic


It sounds like the sensor in the resevoir. Try unplugin and plugin it back in to clean the contacts.

Make sure that your radiator hoses are not colapsing.

If it is leaking into the engine,you will see it on the oil dip stick. The oil will have a milky look to it. But if you say it is not using any, then your oil should look as usual. All cars have to be topped off every once in a while.

checked the oil it is clean.i flushed and filled radiator 2 months ago.were are the contacts on this car.the hoses are fine.should i bleed the air out again.

sensor float can also get stuck inside resivoir. wash out the resivoir (off the car) with soap and water. rinse WELL let dry , replace on car. refill wnd see how it does.

It Is Possible That When You Checked The Coolant Level In The Reservoir And Added Coolant …

… that the radiator was not filled right to the top and sucked the reservoir coolant level down. Or your mark is too low. The reservoir has “Full hot” and “Full Cold” lines on it, sometimes hard to see. Where is your mark? Is it at least above “Full Cold” when the engine is cold? It needs to be. The engine may not be using coolant. As Wizard pointed out this level needs to be checked and replenished (normally, infrequently) periodically. If the coolant was ever changed, it could have burped out some trapped air that was displacing coolant.

I believe these engine cooling systems just have a plastic cap on the reservoir and the tank is not a pressure tank. There is an overflow, if you look closely, near the top, you will see it. I would try filling the tank to “full hot” when its cold and try it. Don’t be alarmed if the tank discharges a little coolant (usually after you park). The tank will seek it’s own full level. Put your new mark there, after it cools.

Follow Simplex’s advice and clean that reservoir! Have someone do it or help if you’re not sure what you’re doing. I had to work at mine with detergent (reservoir taken out of the car!) and a bent coat hanger with a sponge attached to the end to get all the nooks and crannies. Rinse well. Reinstall, Refill.
Good luck!

P.S. How’s that new intermediate steering shaft working for you? Smooth as silk?

put the coolant in the resivor to the full hot you light came on for about 2 to 3 minutes and went off.and stayed off for know.will clean the resivor out and made a new are correct.their is just a plactic cap on resvior not pressurised. flushed and changed coolant 2 months ago.and bleed the air out of the system. will keep you informed of this low coolant light coming on and off.thanks for all the great advice.also i have learned alot about this issue.really helpfull.dominic ps.had the iss replaced on monday what a difference.the car is handling better also.that noise was annoying. had the car inspected at the same time smooth as silk.dont have to hear clicking noise.learned alot about the iss on this site also. still learning want to get to a point were i can do most of the work on the car myself

Dominic, Good Plan.

If I remember, that coolant reservoir is skinny and in kind of a tight spot. I’m not sure how hard it is to get to the fasteners (nuts). If it looks like you can get it out, you might have to raise it a bit in order to disconnect the rubber hose. Keep the hose up to keep coolant in.

Keep checking the coolant level mark and see if the light stays out. Let us know how it’s doing. You’re welcome for the help. Keep learning.