Radiator Cap Spewing Coolant
Thread Starter
Heel & Toe
Joined: Dec 2021
Posts: 24
Likes: 3
From: California
Radiator Cap Spewing Coolant
I recently replaced the heater core. On the first drive today about 10 miles out, running at around 3k RPM (No Overdrve,yet) I began seeing coolant spewing out between the hood and fender where the radiator cap is. I replaced the radiator cap, topped off the coolant and continued on with my journey. A few miles down the road and it began to spew again. The car did not overheat and I did not have this problem prior to the heater core replacement. Any sugestion? The car is a 72 SB.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
Good Belch. Not you, the car.
I suspect that because the coolant was drained for the heater core, the entire system was never belched.
You had air pockets everywhere. When you refill the system, always leave the coolant level 2 -3 inches below the Rad neck. With car idling, watch for coolant movement across the Rad.
A common mistake is to install the Rad Cap immediately. All that does is trap air. Let it idle for several minutes. Be ready with additional coolant. Once the thermo opens the coolant will drop and a big belch will follow.
Having the front end up on ramps or even some 1 X 10s will help immensely. You want the Rad neck at the highest point.
Leave the Rad Cap off until you are satisfied all the air is out.
I suspect that because the coolant was drained for the heater core, the entire system was never belched.
You had air pockets everywhere. When you refill the system, always leave the coolant level 2 -3 inches below the Rad neck. With car idling, watch for coolant movement across the Rad.
A common mistake is to install the Rad Cap immediately. All that does is trap air. Let it idle for several minutes. Be ready with additional coolant. Once the thermo opens the coolant will drop and a big belch will follow.
Having the front end up on ramps or even some 1 X 10s will help immensely. You want the Rad neck at the highest point.
Leave the Rad Cap off until you are satisfied all the air is out.
Thread Starter
Heel & Toe
Joined: Dec 2021
Posts: 24
Likes: 3
From: California
Thanks for the replies. Come to find out it was not the rad cap. The project began with replacing the missing factory A/C compressor, installing new A/C hoses. That led to pulling the dash apart to fix blend door issues and while I had it apart might as well replace the leaking heater core. Anyway what happened was one of the heater core hoses found its way to rub itself on the A/C compressor pulley till it wore thru, lucky for me I had extra hose. Thought I’d go ahead and jack the front up, top off the coolant and let it belch itself while I was at it.
