My stock '89 w/L98 has recently been displaying the low coolant light. The coolant is not low, I have topped it off with the technique of raising the front up and pouring extra coolant in while idle is high. It's temp is good. It seems to come on only five minutes after starting and then goes off at times with no relation to temp. I have pulled the wire off the radiator hookup and cleaned it, but it still keeps coming on! This is a daily driver that is out in the winter weather everyday.
Any thoughts?
Thanks

 

Engine temp has to be above the thermostat opening temp and engine rpm raised. Looking into the filler, you will see the coolant drop out of sight, THEN fill it to the neck, replace the filler cap and let the rpm back down to idle. You still have air in the system, that is why your low coolant light comes on.

 

I also have had this light. it usually comes on on the freeway when accelerating past some loafer on the road.
The answer I found for me is to take the recovery hose off the radiator, cut an inch off the hose and reinstall it with a spring clip type clamp.
The spring type clamp self adjusts with the hose when it shrinks and expands with temp where the worm drive type clamp just is set, If the hose expands with temp, it lets in air instead of drawing coolant back into the radiator when the engine cools.
Even though you have filled the radiator at a high idle, when the pressure kicks the coolant down to the reservoir, with a loose clamp or a split in the hose, or a split tube on the reservoir, it cannot draw in the cooled coolant back into the radiator, and as more and more coolant is expelled into the reservoir, eventually the light comes on for a few seconds, then goes out until it is on all the time.
2. Also, change the radiator cap. if the light check-valve spring in the cap is bad, it can't draw it in either through the cap.

 

Repeat for the next couple of days to ensure all air bubbles have been purged. It can take more than one time to get all the bubbles out the system and have the cooling system packed. Squeeze the upper radiator hose with a rag, and when the hose is not rock hard, the thermostat has opened. This is the time to raise idle, top off the radiator, install cap, and lower the idle. Fill your overflow tank to the proper mark on dipstick also.

Either not all the air bubbles in your system have been purged, or you have an intermittent short to ground along the low coolant sensor circuit.


1. Remove the wire form the low coolant sensor mounted on radiator just below the upper hose. Now check the Low Coolant light inside the car. If it went out, the sensor is bad and a replacement will fix your problem.

2. If the Low Coolant light still stays on even with the plug removed from the low coolant sensor on the radiator, unplug the Low Coolant Module. It's located under the passenger side hush panel. Remove the hush panel, stick your head under the dash, and look straight up.

Low Coolant Module looks like this with a 4 wire connector:

http://forums.corvetteforum.com/atta...5&d=1199287370
http://forums.corvetteforum.com/atta...6&d=1199287370

3. If the Low Coolant Light now goes out, check that Dark Green wire from the sensor on the radiator, (terminal F on the Low Coolant Module) is not grounded. To do this, connect an ohm meter from the Green wire to ground. There should be no continuity or change on the meter's scale display. If there is, there is a short to ground along this wire. Trace it and fix it. Start under the hood at the sensor on the radiator and work back.

4. If the Low Coolant light still stays on, test the Gray wire (terminal E) of the Low Coolant Module connector for a short to ground. If it's grounded, trace that wire and fix it. It should not be grounded.