Got that right. 
Only the 92-96 LT1/4s have the coolant bleeder screws. 
Cooling system air bubble
Thread Starter
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Joined: Jan 2007
Posts: 83
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From: CT
Cooling system air bubble
I must have tried to purge my cooling system a half dozen times and I still get the Low Coolant light.
If I open the radiator cap when cold the radiator is always full to the top.
When I open the cap at 165 Deg. the tank is still full, but will drop a bit when the motor is revved. I'll add about a pint or so and put the cap back on before letting the motor idle. The recovery tank is always pretty full. There are no leaks and the car does not blow white smoke or smell like antifreeze. The low coolant light is intermittant after warmup.
Am I missing something?
If I open the radiator cap when cold the radiator is always full to the top.
When I open the cap at 165 Deg. the tank is still full, but will drop a bit when the motor is revved. I'll add about a pint or so and put the cap back on before letting the motor idle. The recovery tank is always pretty full. There are no leaks and the car does not blow white smoke or smell like antifreeze. The low coolant light is intermittant after warmup.
Am I missing something?
Burning Brakes
Joined: Nov 2005
Posts: 848
Likes: 1
From: 1992 LT1 6 speed Cayman Islands
Sounds like a bad gasket on the radiator cap that breaks the vacium created when the coolants cools down therefore not allowing the coolant from the overflow tank to be drawn into the radiator.
It is a cheap fix requireing a new radiator cap. This may not be the problem but at least it wont cost you an arm and a leg and is a good place to start
It is a cheap fix requireing a new radiator cap. This may not be the problem but at least it wont cost you an arm and a leg and is a good place to start
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Run the car with radiator cap off. Some water will overflow as it warms up and expands.
Wait till it warms up to around the thermostat temperature. When the thermostat opens, the coolant level will drop a bunch, start filling it.
Once it's full, pull the throttle open. (Don't be a ***** either, bring it up to 3500 rpm or something. Make some noise!) Top it off during this and put the cap back on then let it back down to idle.
Now fill the expansion tank up to the hot level. If the expansion tank is too low, the system can suck air in when it cools. If you overfill it, and the system is purged, the expansion tank will overflow the first time you get it reallly hot, this is normal and is getting the rest out of the system. But after a few heats cycles, small amounts of air will leave the system, forced out by thermal expansion, and it will draw coolant back in when it cools if there's any in the exp tank.
Wait till it warms up to around the thermostat temperature. When the thermostat opens, the coolant level will drop a bunch, start filling it.
Once it's full, pull the throttle open. (Don't be a ***** either, bring it up to 3500 rpm or something. Make some noise!) Top it off during this and put the cap back on then let it back down to idle.
Now fill the expansion tank up to the hot level. If the expansion tank is too low, the system can suck air in when it cools. If you overfill it, and the system is purged, the expansion tank will overflow the first time you get it reallly hot, this is normal and is getting the rest out of the system. But after a few heats cycles, small amounts of air will leave the system, forced out by thermal expansion, and it will draw coolant back in when it cools if there's any in the exp tank.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Also the hose to the overflow tank has to be in good shape. It's possible for it to never leak coolant, but to allow air to be sucked into the system when it cools off.
If this was happening, you'd notice the level on the overflow tank dipstick wouldn't change much from hot to cold.
Mine moves exactly between the cold and hot marks on there.
If this was happening, you'd notice the level on the overflow tank dipstick wouldn't change much from hot to cold.
Mine moves exactly between the cold and hot marks on there.
Le Mans Master
Joined: Jan 2006
Posts: 6,564
Likes: 6
From: Woodstock Georgia
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Le Mans Master
Joined: Feb 2000
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From: Kempner Texas
Like CentralCoaster said, get the RPMs up and keep them there while you top-off the radiator AND KEEP THEM THERE UNTIL THE RADIATOR CAP IS TIGHTENED BACK IN PLACE. DON'T LET THE RPMs DROP BACK TO IDLE!
Unless you have drilled holes in the thermostat, the stat MUST be open for any air to purge to the radiator cap area. So we're talking 180 degrees f or higher. It's at the radiator cap area of the radiator that any air is expelled from the engine, so the thermostat has to be open to allow any air to travel to the cap area and out.
Depending on the temp of the stat opening, the coolant WILL BE HOT, so be careful not to get burned. If you happen to close the throttle by accident, HOT coolant will back flow right onto your hand.
Hope this helps.
Jake
Unless you have drilled holes in the thermostat, the stat MUST be open for any air to purge to the radiator cap area. So we're talking 180 degrees f or higher. It's at the radiator cap area of the radiator that any air is expelled from the engine, so the thermostat has to be open to allow any air to travel to the cap area and out.
Depending on the temp of the stat opening, the coolant WILL BE HOT, so be careful not to get burned. If you happen to close the throttle by accident, HOT coolant will back flow right onto your hand.
Hope this helps.
Jake
