Low Coolant Lights keeps coming on!
Thread Starter
Le Mans Master
Joined: Mar 2001
Posts: 9,464
Likes: 1
From: Modesto CA
Low Coolant Lights keeps coming on!
The Low Coolant light keeps coming on in my 87. It just comes on and goes off at random. I filled the cooling system up completely just the other day. My friend suggested that it may be my radiator cap not holding pressure. Could this be? The coolant temps are PERFECT, haven't gotten above 200º. Any ideas?
Le Mans Master
Joined: Jul 2001
Posts: 8,181
Likes: 2
From: Santa Maria, CA
Re: Low Coolant Lights keeps coming on! (TIMSPEED)
You burped your system? As it comes up to op temp, make sure to turn on heater to max and fill again.
Also, I think that sensor "measures" the ph or something of the coolant. It may be signalling a weak mix?
BTW, mine does this like crazy also.
Also, I think that sensor "measures" the ph or something of the coolant. It may be signalling a weak mix?
BTW, mine does this like crazy also.
Burning Brakes
Joined: Dec 1999
Posts: 765
Likes: 11
Cruise-In I Veteran
Re: Low Coolant Lights keeps coming on! (TIMSPEED)
On mine, the overflow hose was swelled and/or the little clamp went bad, and it was siphoning air into the radiator when it was cooling down, thus setting off the sensor. Eventually, it would pull coolant in from the expansion tank and it would turn the coolant light off. If you can pull the overflow hose off the rad fitting, reclamp it with a gear clamp or replace it. It might work for you. Could also be a bad sensor. Good luck.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Low Coolant Lights keeps coming on! (TIMSPEED)
Two things immediately come to mind.
One is a factory defect which GM finally recognized and now offers a replacement sensor to correct the problem. I don't recall the specific year cars involved though but the problem came out in a GM Tech Bulletin some time back.
Two is what was already mentioned. That there is air in the system and when the engine revs, coolant level drops in the radiator, exposing the sensor to air causing the light to illuminate.
Assuming no leaks, bad cap or hose(s), burping's the answer.
Set the heater controls to fullblast and with the engine idling at about 100 degrees F, carefully removed the radiator cap. Let the engine continue to idle until the coolant temp get high enough to allow the thermostat to fully open.
Have you bottle of antifreeze/water mix at the ready. Now reach over and bring the engine up to about 2000 RPMs and HOLD IT THERE.
FROM THIS POINT ON, WITH THE CAP OFF, DON'T LET THE ENGINE SPEED DROP OR YOU'LL GET A HOT COOLANT BATH.
While holding it at 2000, pour in you mix until the radiator is completely full and air bubbles in the mix disappear. Replace the radiator cap, align cap arrow with over-flow hose, and allow the engine to return to idle.
The coolant system is now as full as you can get it and any excess will be expelled to the over-flow bottle.
Hope this helps.
Jake
[Modified by JAKE, 5:17 PM 1/6/2002]
One is a factory defect which GM finally recognized and now offers a replacement sensor to correct the problem. I don't recall the specific year cars involved though but the problem came out in a GM Tech Bulletin some time back.
Two is what was already mentioned. That there is air in the system and when the engine revs, coolant level drops in the radiator, exposing the sensor to air causing the light to illuminate.
Assuming no leaks, bad cap or hose(s), burping's the answer.
Set the heater controls to fullblast and with the engine idling at about 100 degrees F, carefully removed the radiator cap. Let the engine continue to idle until the coolant temp get high enough to allow the thermostat to fully open.
Have you bottle of antifreeze/water mix at the ready. Now reach over and bring the engine up to about 2000 RPMs and HOLD IT THERE.
FROM THIS POINT ON, WITH THE CAP OFF, DON'T LET THE ENGINE SPEED DROP OR YOU'LL GET A HOT COOLANT BATH.
While holding it at 2000, pour in you mix until the radiator is completely full and air bubbles in the mix disappear. Replace the radiator cap, align cap arrow with over-flow hose, and allow the engine to return to idle.
The coolant system is now as full as you can get it and any excess will be expelled to the over-flow bottle.
Hope this helps.
Jake
[Modified by JAKE, 5:17 PM 1/6/2002]
Race Director
Joined: Sep 2000
Posts: 12,182
Likes: 1
From: Partying with the Cowboys cheerleaders in Mt. Olive, New Jersey
Re: Low Coolant Lights keeps coming on! (JAKE)
Jake is absolutely right. My '86 had this problem a couple years back and it took a while to figure it out. By the way, do check the connecting hose from the top of the radiator and the overflow tank. Make sure the connection is air tight. Very important! :yesnod:
