c6 ls3 coolant overflow
Thread Starter
5th Gear
Joined: Oct 2015
Posts: 5
Likes: 0
c6 ls3 coolant overflow
i have a c6 LS3 vette with about 37,000 miles on it the previous owner didnt drive it hard, anyway the coolant started coming out the overflow tube. Dont tell me i have blown head gaskets the oil was just changed and it wasnt a milkshake, so ive come down to 2 things the pressure cap wasnt on correct, or theres a bubble in the system somewhere... anyone else have the same thing happen... could it be something else
Race Director
Joined: Dec 2013
Posts: 12,502
Likes: 3,629
Could be that the fan did not come on to cool the engine down to start with.
Start the car, turn on the A/C with the rec button pushed (light on, on the button), and make sure that the fan comes on. If the fan does not come on, chances are you have a burn fan connector from a tune that is pushing the fan too hard.
Next, get under the car firstly to check the front of the radiator to make sure that you did suck up a garage back and have the front flow to it blocked. If not blocked there, then remove the radiator top cover to look between the front of the motor radiator and A/C radiator for crap packed between the two instead.
From there, drive the car and kick the DIC over to rad temp so you can keep a close eye on it to make sure that the engine temp sensor it working correctly.
Start the car, turn on the A/C with the rec button pushed (light on, on the button), and make sure that the fan comes on. If the fan does not come on, chances are you have a burn fan connector from a tune that is pushing the fan too hard.
Next, get under the car firstly to check the front of the radiator to make sure that you did suck up a garage back and have the front flow to it blocked. If not blocked there, then remove the radiator top cover to look between the front of the motor radiator and A/C radiator for crap packed between the two instead.
From there, drive the car and kick the DIC over to rad temp so you can keep a close eye on it to make sure that the engine temp sensor it working correctly.
Race Director
Joined: Sep 2009
Posts: 11,338
Likes: 2,438
From: Eastern
One cause of an overflowing coolant reservoir is a reservoir cap that isn't sealing properly. This prevents the coolant from being drawn back into the radiator as the engine cools when the engine is turned off.
There has been threads about the cap on some LS2 and LS3's not sealing properly. Try a new cap, and hopefully this will solve your issues.
Have you checked to make sure the Radiator fan is coming on?
It could be a bad Coolant sensor if the fan is not starting.
Some issues have also occurred with the electrical connector at the fan.
Normal coolant temps with a factory thermostat should be 200-210 F at highway speeds. 220 F seems a little high, although it could go that high in the heat of the summer while idling at a stop light.
Good Luck
There has been threads about the cap on some LS2 and LS3's not sealing properly. Try a new cap, and hopefully this will solve your issues.
Have you checked to make sure the Radiator fan is coming on?
It could be a bad Coolant sensor if the fan is not starting.
Some issues have also occurred with the electrical connector at the fan.
Normal coolant temps with a factory thermostat should be 200-210 F at highway speeds. 220 F seems a little high, although it could go that high in the heat of the summer while idling at a stop light.
Good Luck
Thread Starter
5th Gear
Joined: Oct 2015
Posts: 5
Likes: 0
One cause of an overflowing coolant reservoir is a reservoir cap that isn't sealing properly. This prevents the coolant from being drawn back into the radiator as the engine cools when the engine is turned off.
There has been threads about the cap on some LS2 and LS3's not sealing properly. Try a new cap, and hopefully this will solve your issues.
Have you checked to make sure the Radiator fan is coming on?
It could be a bad Coolant sensor if the fan is not starting.
Some issues have also occurred with the electrical connector at the fan.
Normal coolant temps with a factory thermostat should be 200-210 F at highway speeds. 220 F seems a little high, although it could go that high in the heat of the summer while idling at a stop light.
Good Luck
There has been threads about the cap on some LS2 and LS3's not sealing properly. Try a new cap, and hopefully this will solve your issues.
Have you checked to make sure the Radiator fan is coming on?
It could be a bad Coolant sensor if the fan is not starting.
Some issues have also occurred with the electrical connector at the fan.
Normal coolant temps with a factory thermostat should be 200-210 F at highway speeds. 220 F seems a little high, although it could go that high in the heat of the summer while idling at a stop light.
Good Luck
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Race Director
Joined: Sep 2009
Posts: 11,338
Likes: 2,438
From: Eastern
If coolant has been changed/flushed and not purged of air, then it may take awhile before all the air pockets are dissipated.
The best way to find out if you have air in the system is to start a car when it's cold with the Reservoir cap removed and take notice if air bubbles start to appear in the tank. If there is air, it will go to the tank and shrink the fluid level. Add Antifreeze as needed if the level drops.
Once the engine gets to operating temp, turn your heat up in the car to max, and put the fan on high. This will allow coolant to flow through the heater core and extract any air trapped in there as well.
Good Luck
Le Mans Master
Joined: Dec 2004
Posts: 5,492
Likes: 807
From: West coast CA
Air in the system is not a common phenomenon if a coolant change or flush has never been performed.
If coolant has been changed/flushed and not purged of air, then it may take awhile before all the air pockets are dissipated.
The best way to find out if you have air in the system is to start a car when it's cold with the Reservoir cap removed and take notice if air bubbles start to appear in the tank. If there is air, it will go to the tank and shrink the fluid level. Add Antifreeze as needed if the level drops.
Once the engine gets to operating temp, turn your heat up in the car to max, and put the fan on high. This will allow coolant to flow through the heater core and extract any air trapped in there as well.
Good Luck
If coolant has been changed/flushed and not purged of air, then it may take awhile before all the air pockets are dissipated.
The best way to find out if you have air in the system is to start a car when it's cold with the Reservoir cap removed and take notice if air bubbles start to appear in the tank. If there is air, it will go to the tank and shrink the fluid level. Add Antifreeze as needed if the level drops.
Once the engine gets to operating temp, turn your heat up in the car to max, and put the fan on high. This will allow coolant to flow through the heater core and extract any air trapped in there as well.
Good Luck
In my experience these cars will burp out all the air they've got in one warmup following a coolant change.
