low coolant light
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Joined: May 2013
Posts: 84
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From: Fort Bragg NC
low coolant light
So I am back to work on my '86. My low coolant light first came on after I did a drain and refill but not a true flush. At that time I was low and have ensured several times that the coolant was not low from then on...which it is now clearly visible when I take off the radiator cap. So now the light comes on and turns off while I am driving as if it is a bad reading. My question is, how the hell do I get the light to stay off? I looked into how the thermostat opens and closes but I don't understand what could make the light come and go.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
Does not mean system is completely full and air free
You most likely still have air pockets in the system.
Need to "burp ' the system to get the correct fill level.
Warm engine to stat open temp .Remove the rad cap , raise revs to 2k , you will see the coolant level in the radiator drop.
Add more coolant while holding the revs up , replace cap before dropping back to idle.
Need to "burp ' the system to get the correct fill level.
Warm engine to stat open temp .Remove the rad cap , raise revs to 2k , you will see the coolant level in the radiator drop.
Add more coolant while holding the revs up , replace cap before dropping back to idle.
Team Owner
Joined: Sep 2003
Posts: 20,179
Likes: 673
From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
That is to remove the sensor without breaking the plastic clips on the sensor?
The clips that become brittle and break easy when removed?
And if either clip is broken the sensor must be replaced with new?
The OP needs to know this procedure can leave him stranded until a part is available.
Last edited by JrRifleCoach; Jan 8, 2014 at 01:29 AM.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I fixed that problem on my car by replacing the radiator cap.
If it's not working correctly it won't let the system purge the air out of itself. Also you need to make sure to keep enough coolant in the overflow tank for the system to suck back in coolant after it pushes out the excess air.
If it's not working correctly it won't let the system purge the air out of itself. Also you need to make sure to keep enough coolant in the overflow tank for the system to suck back in coolant after it pushes out the excess air.
Melting Slicks
Joined: Aug 2008
Posts: 2,082
Likes: 50
From: Palmdale CA
If the cooling system is full, and free from air, then there is a problem with the level probe/circuit. This is what CC calls out for a probe.
Item [244165 probe] [664491 connector] reference.
http://www.parts123.com/parts123/yb....rt~A2~cadefibF
Item [244165 probe] [664491 connector] reference.
http://www.parts123.com/parts123/yb....rt~A2~cadefibF
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
The problem is most likely what everyone is telling you, there are air pockets still in the system.. You can either burp the system to get the air out. If you have a thermostat with the hole in it like the Stant Super stat or drill your own holes in your thermostat, then you can run the car through a few heat cycles and it most likely will purge itself...This has been a problem with the C4s since they started making them in 84. I had so much trouble getting my 89 to purge that I spent $117.00 on a Airlift System so I could fill my cooling system with just coolant and not have to worry about air getting in the system....
...WW
Read about my Airlift Coolant Refill System....
http://forums.corvetteforum.com/c4-t...ere-it-is.html.
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...WWRead about my Airlift Coolant Refill System....
http://forums.corvetteforum.com/c4-t...ere-it-is.html.
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Last edited by WW7; Jan 8, 2014 at 07:31 AM.
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
[QUOTE=JrRifleCoach]...Just curious, have you ever accomplished this task?
That is to remove the sensor without breaking the plastic clips on the sensor?
The clips that become brittle and break easy when removed?
And if either clip is broken the sensor must be replaced with new?
The OP needs to know this procedure can leave him stranded until a part is available./QUOTE]
Yes, have replaced many sensors on C4s without breaking any clips.
If a sensor is damaged during removal, I think you will find that the replacement cost of a sensor is quite inexpensive, and they are readily available
My post was just to convey what OTHERS had posted to remedy their 'low coolant' light, not a cure-all suggestion.
That is to remove the sensor without breaking the plastic clips on the sensor?
The clips that become brittle and break easy when removed?
And if either clip is broken the sensor must be replaced with new?
The OP needs to know this procedure can leave him stranded until a part is available./QUOTE]
Yes, have replaced many sensors on C4s without breaking any clips.
If a sensor is damaged during removal, I think you will find that the replacement cost of a sensor is quite inexpensive, and they are readily available
My post was just to convey what OTHERS had posted to remedy their 'low coolant' light, not a cure-all suggestion.
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Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
[QUOTE=seabright;1585863922]
The OP said the light was going on and off as he was driving around... If the sensor were bad it should either stay on all the time, or stay off all the time..A few times when my cooling system had air in it, the light would come on when I hit the gas , and go off when I let off the gas.......Because of the way it's acting, I doubt it's the sensor..JrRiflecoach is right when he says it's real hard to get the sensor out without breaking the prongs, I have never been able to remove one of the original ( 20+ year old) sensors without breaking off a prong or two...
...WW
Originally Posted by JrRifleCoach
...Just curious, have you ever accomplished this task?
That is to remove the sensor without breaking the plastic clips on the sensor?
The clips that become brittle and break easy when removed?
And if either clip is broken the sensor must be replaced with new?
The OP needs to know this procedure can leave him stranded until a part is available./QUOTE]
Yes, have replaced many sensors on C4s without breaking any clips.
If a sensor is damaged during removal, I think you will find that the replacement cost of a sensor is quite inexpensive, and they are readily available
My post was just to convey what OTHERS had posted to remedy their 'low coolant' light, not a cure-all suggestion.
That is to remove the sensor without breaking the plastic clips on the sensor?
The clips that become brittle and break easy when removed?
And if either clip is broken the sensor must be replaced with new?
The OP needs to know this procedure can leave him stranded until a part is available./QUOTE]
Yes, have replaced many sensors on C4s without breaking any clips.
If a sensor is damaged during removal, I think you will find that the replacement cost of a sensor is quite inexpensive, and they are readily available
My post was just to convey what OTHERS had posted to remedy their 'low coolant' light, not a cure-all suggestion.
...WW
Last edited by WW7; Jan 8, 2014 at 09:45 PM.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
I believe it is a problem we all had as newby owners.
We filled the radiator up the same as every other car we owned , then had the low coolant light come on having us go WTF; it is full to the top.
Only coming here gave us the correct info on how to remedy ( one of the 1st questions I asked 10 years ago )
Thread Starter
Advanced
Joined: May 2013
Posts: 84
Likes: 0
From: Fort Bragg NC
Does not mean system is completely full and air free
You most likely still have air pockets in the system.
Need to "burp ' the system to get the correct fill level.
Warm engine to stat open temp .Remove the rad cap , raise revs to 2k , you will see the coolant level in the radiator drop.
Add more coolant while holding the revs up , replace cap before dropping back to idle.
You most likely still have air pockets in the system.
Need to "burp ' the system to get the correct fill level.
Warm engine to stat open temp .Remove the rad cap , raise revs to 2k , you will see the coolant level in the radiator drop.
Add more coolant while holding the revs up , replace cap before dropping back to idle.
Thread Starter
Advanced
Joined: May 2013
Posts: 84
Likes: 0
From: Fort Bragg NC
Okay, so thanks for the term "burping" guys. I YouTube's a couple videos and I think I got it. I saw one that had this spill free funnel thing so I am going to make me something like that so I don't make another mess. And then I am done once it stops going down and I don't see any bubbles. Thanks everyone!
Team Owner
Joined: Sep 2003
Posts: 20,179
Likes: 673
From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Its a fact that purging/burping the C4 L98 water system is absolutely necessary.
I always drill a hole in the t-stat to help purge off the air in any engine.
Burping includes running the engine speed up to 2000-2500 RPM and continue pouring in water. As the stat opens there may be rush of water out the neck so crank up the engine to ensure there is nothing but water in there and quickly tighten the cap before dropping the engine speed. Fill the water catcher up to the top or close and take her for a nice drive and park overnite. Check the catch bottle in the morning and see how much the system has sucked it down. You might want to take another short drive and park until cool before you go for a cruise.
Yes it will be messy! And you might be seeing that light again.
The light can be disabled temporarily by jumping the connector to ground.
It's better to ignore the light until it extinguishes on its own.
I always drill a hole in the t-stat to help purge off the air in any engine.
Burping includes running the engine speed up to 2000-2500 RPM and continue pouring in water. As the stat opens there may be rush of water out the neck so crank up the engine to ensure there is nothing but water in there and quickly tighten the cap before dropping the engine speed. Fill the water catcher up to the top or close and take her for a nice drive and park overnite. Check the catch bottle in the morning and see how much the system has sucked it down. You might want to take another short drive and park until cool before you go for a cruise.
Yes it will be messy! And you might be seeing that light again.
The light can be disabled temporarily by jumping the connector to ground.
It's better to ignore the light until it extinguishes on its own.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
Never had a problem
The radiator appears full , raising and holding the revs lowers the level.
Add coolant required to fill, replace cap , drop revs.
NO mess
Not sure what videos you are whatching
Did you read what has been posted above?
Burping a C4 is adding coolant to completely fill the system and get rid of air pockets ;
not looking for bubbles
The radiator appears full , raising and holding the revs lowers the level.
Add coolant required to fill, replace cap , drop revs.
NO mess
Not sure what videos you are whatching
Did you read what has been posted above?
Burping a C4 is adding coolant to completely fill the system and get rid of air pockets ;
not looking for bubbles
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
You mentioned having someone else to rev the engine for you... I just take a small piece of cardboard and stick it between the idle adjustment screw and the arm on the throttle body, then push the arm in against the cardboard until the rpms go down to around 2000 rpms, then when your finished filling the radiator just remove the cardboard....It also helps to get the front of the car up about a foot off the ground using jackstands, this makes burping the system alot easier "sometimes".......... .WW
..... .WW
Last edited by WW7; Jan 9, 2014 at 11:32 AM.