Low Coolant Light on this Spring
Thread Starter
Instructor
Joined: Apr 2004
Posts: 115
Likes: 2
From: Kissimmee, FL
Low Coolant Light on this Spring
My 86 has been showing the Low Coolant Light on recently, and the levels, both in the Radiator and Overfill are correct. Hasn't been changed in over 2 years. It only does it when the engine is warm and goes off when going up or down a hill. The Temp is normal at around 180. Any ideas why it is on ? Puzzled !
Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
The engine is lower than the radiator in C4's and with the engine off and the radiator cap removed, the coolant looks full but there is an air bubble in the block and when the water pump starts moving the coolant, the coolant level drops and turns on the low coolant light. I agree with Vader86, fill your radiator with the engine slightly racing and up to the opening temp of the thermostat, then put the radiator cap back on and let the idle speed back down.
Team Owner
Joined: Dec 1999
Posts: 34,873
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
It depends on the amount of coolant in the system. I've had the coolant level in my 87 be a good 5" below the filler neck and I never saw temps much above what the car usually runs at. As long as there is coolant flow and the radiator can effectively cool the liquid, it should be OK.
Cooluing systems probably have more than enough coolant to keep an engine at the correct operating temps.
Cooluing systems probably have more than enough coolant to keep an engine at the correct operating temps.
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Drifting
Joined: Mar 2004
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From: Grand Rapids Mi
After a dozen+ years of early style C-4's [overflow ahead of front wheel] I'm resigned to fact that occassionally if car hasn't been driven for awhile I'm going to have coolant warning light! 
Have tried new sensor and a few other recommends. Never seem to hear this complaint once overflow tank went back to cowl upper right hand side. 
Have tried new sensor and a few other recommends. Never seem to hear this complaint once overflow tank went back to cowl upper right hand side.
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Joined: Sep 2001
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From: Athens AL
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Originally Posted by RRT vette
If the coolent system had air in it, wouldn't the temps run hotter than 180*?
Melting Slicks
Joined: Feb 2006
Posts: 2,753
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From: backwoods upstate ny
every time i drop the coolant to service something, it takes about a week of adding a tiny amount of coolant to a ''full'' system before the low coolant lite gets tired of the game....normal,irritating,but normal.
coolant 2 years old is about ready to be replaced anyway...it turns acidic and begins to digest things,especially aluminum things like radiators and cylinder heads
coolant 2 years old is about ready to be replaced anyway...it turns acidic and begins to digest things,especially aluminum things like radiators and cylinder heads
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Originally Posted by C-4 Now
After a dozen+ years of early style C-4's [overflow ahead of front wheel] I'm resigned to fact that occassionally if car hasn't been driven for awhile I'm going to have coolant warning light!
Originally Posted by redrose
every time i drop the coolant to service something, it takes about a week of adding a tiny amount of coolant to a ''full'' system before the low coolant lite gets tired of the game....normal,irritating,but normal.
Originally Posted by c4cruiser
It depends on the amount of coolant in the system. I've had the coolant level in my 87 be a good 5" below the filler neck and I never saw temps much above what the car usually runs at.
Thread Starter
Instructor
Joined: Apr 2004
Posts: 115
Likes: 2
From: Kissimmee, FL
Light still on
The light still goes on and I have noticed after I shut off the engine, there is a small puddle of Coolant that is leaking from the Rad. Cap. Going to replace it and see if the light stays off. Otherwise, got to be a Sensor problem.
Thread Starter
Instructor
Joined: Apr 2004
Posts: 115
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From: Kissimmee, FL
No leak - light still on
Well a new Cap fixed the leak, but the light still goes on but randomly. Doesn't always stay on, only every once in a while. I am thinking the Sensor. But, since the coolant will need changing soon, should I change it first and then see if the problem goes away ?
Do you nedd to remove the Knock Plugs when changing the coolant on an 86 ? I have been told not to use a Flush treatment and only use water to flush clean.
Do you nedd to remove the Knock Plugs when changing the coolant on an 86 ? I have been told not to use a Flush treatment and only use water to flush clean.
Drifting
Joined: May 1999
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From: Sacramento, CA Money can't buy happiness - but it's more comfortable to cry in a Corvette than a Yugo.
Sometimes the coolant sensor gets crud around where it plugs into the radiator under the cap, or just gets a coating on the sensor itself. Notice that it has only one wire, so it is very sensitive to proper ground issues. I'd try pulling it out and cleaning off the sensor and the area where it screws into the radiator real well. Make sure it is clean and tight when you put it back into the radiator housing. Easy 10 minute job and often fixes this type of issue. Then be sure you properly purge/burp the system again as you will allow air into the radiator doing this.
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From: North Yorkshire, England
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John, The guys have already covered this in detail, but just for your reference, here is the TSB (Technical Service Bulletin):Low Coolant Warning Light
The clamps on the hoses to the recovery tank are important as when the engine cools, it tries to draw the coolant expelled into the recovery tank back into the radiator. If the clamps aren't good and tight, the system will suck air into the system, but not leak coolant. The results are the same, LOW COOLANT light.
Good Luck.
The clamps on the hoses to the recovery tank are important as when the engine cools, it tries to draw the coolant expelled into the recovery tank back into the radiator. If the clamps aren't good and tight, the system will suck air into the system, but not leak coolant. The results are the same, LOW COOLANT light.
Good Luck.