Antifreeze Spilling Out of Rad Cap

[Pat H.]

I just rebuilt my 59 283-230 engine and it seems to run fine. The problem is that antifreeze keeps coming out from the rad cap. I had the rad checked before installing it and have tried 3 different rad caps at 7#. I have the correct Harrison Copper rad. I thought this was the normal as "it will find its own level", but after a 150 miles it should have settled by now. I'm running a 160 degree Thermostat and a 50-50 mix of Peak antifreeze. So far the temp gauge has climbed to approx 190 degrees in traffic but normally runs at about 170. Any suggestions?

[Joe M.]

Re: Antifreeze Spilling Out of Rad Cap

Check to see if the neck of the radiator is smooth. If you had not tried 3 caps, I would say it was a bad cap, but not three. Something has changed about the radiator neck that is not allowing the caps to seat properly. Feel for a burr, a raised bump, or a dipped out place. the operating temps you describe should not force the fluid out of the caps.

[John H.]

Re: Antifreeze Spilling Out of Rad Cap

I just rebuilt my 59 283-230 engine and it seems to run fine. The problem is that antifreeze keeps coming out from the rad cap. I had the rad checked before installing it and have tried 3 different rad caps at 7#. I have the correct Harrison Copper rad. I thought this was the normal as "it will find its own level", but after a 150 miles it should have settled by now. I'm running a 160 degree Thermostat and a 50-50 mix of Peak antifreeze. So far the temp gauge has climbed to approx 190 degrees in traffic but normally runs at about 170. Any suggestions?

Pat -

Is the coolant coming out of the overflow hose, or from where the metal gasket in the top of the cap seals to the top edge of the filler neck? The primary pressure seal for the cap is where the black rubber gasket below the coil spring seals against the smaller-diameter surface about 1/2" down from the top of the filler neck.

[Pat H.]

Re: Antifreeze Spilling Out of Rad Cap

John,
Its appears to be coming out at the cap and not the overflow. I originally had a GM service part on my direct fit (thats a joke) rad and had no problem. Then I put a Dewitt repop on and it was okay. I'll check the neck to ensure it's smooth and has no dips in it

[John H.]

Re: Antifreeze Spilling Out of Rad Cap

John,
Its appears to be coming out at the cap and not the overflow. I originally had a GM service part on my direct fit (thats a joke) rad and had no problem. Then I put a Dewitt repop on and it was okay. I'll check the neck to ensure it's smooth and has no dips in it

Pat -

Photo below shows how the cap works in both pressure relief mode and in vacuum relief mode.


RadCapScan.jpg

[Pat H.]

Re: Antifreeze Spilling Out of Rad Cap

John,
I found a leak in the metal overflow tube. It appears that the solder/weld is cracked from being handled too many times. Can this be repaired on the car and what would you suggest to make the repair or does it have to come out and go to a rad shop?

[John H.]

Re: Antifreeze Spilling Out of Rad Cap

John,
I found a leak in the metal overflow tube. It appears that the solder/weld is cracked from being handled too many times. Can this be repaired on the car and what would you suggest to make the repair or does it have to come out and go to a rad shop?

Pat -

That should be a solder joint, and should be repairable on the car with a propane torch, flux, and solder after removing any paint from the joint area, assuming it's easily acccessible. Surround the area with wet rags and be careful.