Help! Low Coolant light

[tcolyer]

Having an issue with my '86; started last fall the low coolant light would come on occasionally but the reservoir was ok and when removing cap the radiator seemed ok. Pressure tested and it did lose pressuer slightly. I replaced all hoses, water pump and flushed the coolant system and refilled and also addd barsleak. Last week it started again - check everything radiator was clean and full but reservor was very dirty, so I reflushed radiator and cleaned the reservoir, replaced the antifreeze but did not readd the barsleak. Now the low collant light is on most of the time

Have I not got all the air out or could I have leaking head gaskets??

 

[boomdriver]

Having an issue with my '86; started last fall the low coolant light would come on occasionally but the reservoir was ok and when removing cap the radiator seemed ok. Pressure tested and it did lose pressuer slightly. I replaced all hoses, water pump and flushed the coolant system and refilled and also addd barsleak. Last week it started again - check everything radiator was clean and full but reservor was very dirty, so I reflushed radiator and cleaned the reservoir, replaced the antifreeze but did not readd the barsleak. Now the low collant light is on most of the time

Have I not got all the air out or could I have leaking head gaskets??

Are you loosing coolant? is there foam on the dip-stick or the PCV valve? Is there foam or oil in the filler neck of the radiator? if no to all the above, then the sensor is just fouled.
What you might have is a partially clogged radiator and a coat of slime on the tip of the low coolant sensor.
NEVER use that BarsLeaks or any of those gasket in a can products.
Stop-leak products are the DEVIL ad

I did it a few years ago in an attempt to get a couple more days out of a leaking head gasket.
When the head was removed, I saw the rear coolant passage in the head CLOSED completely with the 'stop-leak' garbage. No coolant circulation in the rear of that cyl head. Fortunately I did'nt run it more than a few miles and it never got hot.
Not trying to be an ass, but trying to give you fair warning...that stuff does more damage than good.

The low coolant sensor is very easy. Its simply a circuit that gets complete when the water covers its tip. If the water level gets below the tip, the circuit is broken and the lite comes on. OR, when the tip is covered with a non-conductive layer of something, the circuit is broken.

If you pull the thing out and clean it, and stick it back in with a thin smear of silicone on the rubber, it'll probably be fine.Clean the hole with a pipe-cleaner or similar device. You DO risk breaking the rubber seal but if you do its an easy fix by drying the hole and plugging with silicone until a new sensor can be had. New ones are only a few dollars and you can even make one. Its just a single metal blade that is insulated from the radiator but can reach into the water.

 

[tcolyer]

Thanks, I think you are right - just started car in garage and low coolant light was on. Removed radiator cap - light still on and the radiator was completely full. So I must have a fouled sensor.

So now to decide to clean or replace - radiator and sensor is only 2 yrs old Delco radiator.

 

[vetteoz]

Have I not got all the air out

Did you " burp " the system correctly?
Just filling radiator is not the right way on these cars

 

[tcolyer]

Yes, I think I did. filled, waited till thermostat opened then ran car at high idle (2000)and added fluid, then quickly put cap on.

 

[boomdriver]

Did you " burp " the system correctly?
Just filling radiator is not the right way on these cars

For $12 you can add a nice little valve with a water-hose fitting to end the burping FOREVER ! fill with coolant, connect water hose to your flush valve, turn water on crack flush valve to on, start car and watch it over-fill out the res cap or the radiator overfill vent,...either way its full. Close valve, d/c hose. Good To Go.
Great system for flushing too.

 

[tonybabb]

Could be a design problem...

Believe it or not it could be a design problem.
I bought my 89 coupe new in 89 and it came with a paper insert from GM that said it was possible that the low coolant light would come on from time to time. It went on to say just monitor the coolant temp to be sure it's not overheating and the problem should go away in a few days - assuming you drive it daily. It tends to happen more frequently after I've changed the antifreeze, maybe several times over a period of a few months and then doesn't happen again for months or even years.

 

[tcolyer]

Thanks for your help -it seemed to be a fouled sensor. I removed the sensr and polished with scotch bright and it is now working perfectly.

Thanks again for the ideas.

 

[Bolisk]

Where is the sensor in an 1989? Have the same problem.

 

[tcolyer]

The sensor on an 89 is in same location as mine - look at radiator cap - then below the upper transmission line connection you should see a one wire conection.

 

[tcolyer]

Weird - light started coming on again immediately took oout sensor and it was discolored but nothing stuck on it. cleaned again and is working. What would make it turn off color so fasr - anitfreeze Prestone is new and clean - it is a little stronger than 50 / 50. The sensor end was yellow discolored not shiney Steel like the wire end

Any ideas

 

[boomdriver]

Weird - light started coming on again immediately took oout sensor and it was discolored but nothing stuck on it. cleaned again and is working. What would make it turn off color so fasr - anitfreeze Prestone is new and clean - it is a little stronger than 50 / 50. The sensor end was yellow discolored not shiney Steel like the wire end

Any ideas

Theres something circulating in there other than new prestone...

Sounds like some remaining stop leak .

Thats why I'll use the drill pump to suck out as much as possible, then connect the garden hose to the flush valve installed in the heater hose and flush & run the motor for several minutes to get ALL the stuff out.

Before doing this, I ruined new coolant several times. Because I like the 5/50k dex and its low risk to aluminum , I like to see that stuff as crystal clean orange as it was when poured from the jug.

Another note, I also use Water Wetter and have not had any adverse effects like the sensor fouling. If it helps with 2 degrees heat exchange, its worth adding.

 

[Bolisk]

how do you remove the sensor without damanging it?

 

[tcolyer]

Latest update

Thanks for your help -it seemed to be a fouled sensor. I removed the sensr and polished with scotch bright and it is now working perfectly.

Thanks again for the ideas.

They low coolant light is /was still giving me problems. Over the last few months every 5 - 6 wks I have to clean the sensor. So I decided to buy a spare sensor, I found someone with AC Delco parts on EBay. It was delivered yesterday and I replaced the one in the radiator. While doing so, I compared the two units. The one that came in the replacment radiator was 1/2 the size of the probe on the new AC Delco.
I am presuming that since it is conducting (or grounding thru the coolant) to keep the light off, that with a larger surface area to conduct I will not have this problem again.

Any comments appreciated.