Overflow tank not refilling cooling system
Thread Starter
Melting Slicks
Joined: Jan 2002
Posts: 3,293
Likes: 79
From: Jackson MI
Overflow tank not refilling cooling system
Guys,
My overflow tank is full to the brim, but this weekend my car was well low on coolant. It wasn't bone dry but low enough that the car was having problems cooling. What causes the coolant to flow backwards back into the cooling system from the overflow tank???? or is it not going to? This is on a '93 LT1. Any suggestions would help. Thanks guys.
My overflow tank is full to the brim, but this weekend my car was well low on coolant. It wasn't bone dry but low enough that the car was having problems cooling. What causes the coolant to flow backwards back into the cooling system from the overflow tank???? or is it not going to? This is on a '93 LT1. Any suggestions would help. Thanks guys.
Burning Brakes
Joined: Nov 2005
Posts: 848
Likes: 1
From: 1992 LT1 6 speed Cayman Islands
This problem is usually caused bt a bad rubber seal in the radiator cap. Replace the cap with a new 16 Lb one and it should suck the water into the radiator as it cools.
The way it works is that when there is air in the cooling system, this air is heated by the engine, expands and is released by the spring vent in the radiator cap, to the overflow bottle. As the engine cools and the water and air in the radiator contracts, it will pull the liquid from the overflow tank if there are no air leaks at the cap, otherwise it will pull air.
The way it works is that when there is air in the cooling system, this air is heated by the engine, expands and is released by the spring vent in the radiator cap, to the overflow bottle. As the engine cools and the water and air in the radiator contracts, it will pull the liquid from the overflow tank if there are no air leaks at the cap, otherwise it will pull air.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
First, that is a very slow and inefficient way to fill your radiator. Fill, burp and bleed the radiator and cooling system. Make sure the coolant recovery tank is at the proper level. A thorough system flush preceding this is never a bad idea. As the cooling system heats up and the coolant expands, the radiator cap allows the coolant to flow into the recovery tank. When the engine cools and the pressure drops in the cooling system, the higher atmospheric pressure will overcome the valve in the radiator cap, and allow the radiator to refill. If your radiator is low, you want to know why. You may have a leak, that eventually, the recovery tank can't make up for. Or you may have a defective radiator cap that won't allow coolant to be drawn back into the cooling system. Test for leaks and test the cap.
RACE ON!!!
RACE ON!!!
Thread Starter
Melting Slicks
Joined: Jan 2002
Posts: 3,293
Likes: 79
From: Jackson MI
Thanks for the advice guys. I checked the upper radiator cap seal and it was torn. Bought a new one last night I'll keep an eye on it . Thanks a bunch, I would never have thought to check out the radiator cap. 
