L98 Cooling System Issues
Thread Starter
1st Gear
Joined: Nov 2010
Posts: 1
Likes: 0
From: Melbourne Victoria
L98 Cooling System Issues
Having some issues with the cooling system in my 1989 c4 L98:
Every morning i start the i get the "Low Coolant" warning, but when the coolant temp hits about 185*F the warning turns off and never appears again till next start-up. Coolant level in radiator is fine when checked before start-up.
-bypassed leaking throttle body and pressure checked hoses - no leaks detected.
-oil had no signs of coolant
-new thermostat installed
-new coolant sensor installed
anyone had this problem before?
cheers
young45a
Every morning i start the i get the "Low Coolant" warning, but when the coolant temp hits about 185*F the warning turns off and never appears again till next start-up. Coolant level in radiator is fine when checked before start-up.
-bypassed leaking throttle body and pressure checked hoses - no leaks detected.
-oil had no signs of coolant
-new thermostat installed
-new coolant sensor installed
anyone had this problem before?
cheers
young45a
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
You can't tell the coolant level by looking into the filler with the engine cold or not running! You can only tell visually if the coolant level is low when the thermostat opens and coolant begins to circulate. If it is low, when coolant begins circulating it will go out of sight when looking into the filler. You fill the coolant by racing the engine slightly when the thermostat is open and filling to the neck of the filler and then closing the radiator cap and let the engine rpm back down to idle. This is called, "burping". The engine sits lower than the radiator, so the coolant stays high when cold and it looks like you have a full system.
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
MY 86 does this occasionally. I installed a blade connector on the frame rail adjacent to the level sensor on the rad. When the light starts to become a problem and I know the coolant level is correct, the connector is unplugged, then plugged into the grounded blade. It'll stay there for the remainder of the run or day, then returned to its original position later.
Safety Car
Joined: Jan 2004
Posts: 3,759
Likes: 8
Sounds like you need to burp the coolant. A quick search you will find the burp procedure. Make sure you have the heater on when burping it.
What you could check is start the car. Then pull the radiator cap and check the level. I bet it'll be low. Also make sure you have enough coolant in the overflow bucket when cold.
What you could check is start the car. Then pull the radiator cap and check the level. I bet it'll be low. Also make sure you have enough coolant in the overflow bucket when cold.
Racer
Joined: Apr 2001
Posts: 302
Likes: 0
From: South Haven Michigan
I had the low coolant light showing up after I had changed coolant and burped the system and it turned out to be the radiator cap. All I can think of is it wasn't quite sealing 100% when it cooled down and wasn't sucking coolant back into the radiator from the overflow. Anyway, that fixed it.
Safety Car
Joined: Jan 2004
Posts: 3,759
Likes: 8
I had the low coolant light showing up after I had changed coolant and burped the system and it turned out to be the radiator cap. All I can think of is it wasn't quite sealing 100% when it cooled down and wasn't sucking coolant back into the radiator from the overflow. Anyway, that fixed it.
On another car, I found the cap to be bad. But I didn't know it as it ran fine and didn't overheat. I found out it was bad when the car was over 200*, and the upper radiator hose could be squeezed when it should have been hard. A new cap fixed that.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
Having some issues with the cooling system in my 1989 c4 L98:
Every morning i start the i get the "Low Coolant" warning, but when the coolant temp hits about 185*F the warning turns off and never appears again till next start-up. Coolant level in radiator is fine when checked before start-up. Anyone had this problem before?
cheers
young45a
Every morning i start the i get the "Low Coolant" warning, but when the coolant temp hits about 185*F the warning turns off and never appears again till next start-up. Coolant level in radiator is fine when checked before start-up. Anyone had this problem before?
cheers
young45a
Your problem is you have air trapped in your cooling system. Air is typically trapped under the thremostat. As Josh Wilson said, you need to drill two small holes in your thermostat and properly purp your cooling system. Here is a how to write-up.
P.
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
Safety Car
Joined: Nov 2008
Posts: 4,328
Likes: 15
From: Jacksonville FL
The low coolant light in my Silverado came on when it was a pint low, not a serious issue. If your light goes out after the car warms up, I would say its probly a minor amount of coolant missing. Do as suggested above and burp your car to solve the issue.
