Antifreeze backflow bubbling
Thread Starter
1st Gear
Joined: Sep 2018
Posts: 1
Likes: 0
From: Colorado
Antifreeze backflow bubbling
1977 Corvette
We had the radiator flushed, added antifreeze/coolant, and when the car is warm, the antifreeze coolant is backing up into the overflow reservoir and bubbling. The temperature is staying steady around 195 to 200 degrees. Some of the forums say it could be an air pocket that needs to be purged. So we took off the radiator cap and run the car. It appears that the thermostat is opening ok because the antifreeze coolant in the radiator is going down, but then it fills up again and regurgitates the coolant in large amounts. It continues to do this until we put the cap back on. This doesn't fix the bubbling problem. Any thoughts or ideas? We checked the oil and there's no water in it.
We had the radiator flushed, added antifreeze/coolant, and when the car is warm, the antifreeze coolant is backing up into the overflow reservoir and bubbling. The temperature is staying steady around 195 to 200 degrees. Some of the forums say it could be an air pocket that needs to be purged. So we took off the radiator cap and run the car. It appears that the thermostat is opening ok because the antifreeze coolant in the radiator is going down, but then it fills up again and regurgitates the coolant in large amounts. It continues to do this until we put the cap back on. This doesn't fix the bubbling problem. Any thoughts or ideas? We checked the oil and there's no water in it.
Last edited by Perry_janet; Sep 3, 2018 at 11:15 AM. Reason: Adding the year model
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
When "purging or burping" the cooling system, leave the coolant level WELL below the filler neck for several minutes. Maybe even five inches. You have to allow a space for the air pockets / bubbles to escape out of the cap-less radiator. And it will take several minutes to complete the procedure. Then when it appears the air pockets have been removed and the coolant level is constant, then add coolant to the necessary level and cap it.
It also helps to have the front end up on ramps. The bubbles will seek the highest point which will then be the filler-neck.
It also helps to have the front end up on ramps. The bubbles will seek the highest point which will then be the filler-neck.
Last edited by HeadsU.P.; Sep 3, 2018 at 06:58 PM.
Safety Car
Joined: Mar 2014
Posts: 3,558
Likes: 548
From: Round Rock Texas
Make sure you have a good seal around your radiator and fan shroud. Also make sure your fan clutch is working as well. I just installed a new air dam as our '72 didn't have one when we bought it. Good luck and welcome to the forum.
Last edited by Jstan2014; Sep 3, 2018 at 04:54 PM.
