The Stovebolt Site Forums The Shop Area Engine Shop Radiator Blues

Hi Stovebolters. I am the new guy. I need help with a recuring radiator problem on my 48, 3/4 ton with a 235 and 4 speed. I searched on the archives and could not find anything that would help. My 48 3/4 is a daily driver and every once in a while, it just throws all the fluid out of the radiator through the overflow. I am not overfilling the radiator, have changed the cap and thermostat, flushed, etc. The hoses are old, but I do not think I am getting air into the system unless the weep hole on the pump is letting some in. I did have probs with the overflow tube sticking into the opening where the cap goes in and not letting it set against the seat. Is the lip that the radiator cap seats against on your machines flat? Mine seems to have an uneven lip. Any help is appreciated. Ths site is great. As soon as I found it, I have read every post. Thanks everybody

Ralph -
Here's what I did to slove the same problem you have. Remove your thermostat and drill a very small hall in the flat part of the thermostat. This hole will act as an air vent to allow trapped air to escape from your cooling system even if the thermostat is closed. Be sure the hole is away from anything that would block it when installed. The lip that the radiator cap seals against does need to be straight enough for the cap rubber to seal. Be sure you have a good (new) cap and that it is the right cap for your application. I also installed an after market overflow tank to catch any discharge as the engines warms. It will pull the fluid back into the radiator as it cools (just like new cars of today). This seems to have solved my problem. Hope it works for you. Good luck!

Thanks for your help 6cylinders. I will give that a try. I have a plastic overflow tank, but did not want to change too much as my truck is all original except for the 235. I am looking for something more period. I will try the small hole in the thermo tonight. It was cold here yesterday and I dont have a garage. Thanks again!!

Ralph

Ralph, is your truck's radiator the original unpressurerized design?If so, the overflow tank won't work properly.You need a modern type cap with the one way valve built in,which requires the over flow to be in the cap neck on the radiator. Is this what you have or are you using the stock sealed cap and have attached the catch tank to the original overflow tube?

An overflow tank will work on an unpressurized system if the overflow tank always has enough coolant mix in it to keep the hose going into the overflow tank submerged in the liquid. I've got a 37 radiator that is not pressurized and the overflow tube actually runs out of the top of the radiator tank. The system works fine. To keep a stock appearence I hid my overflow tank down under the front of the truck. It has been working great for about 12 years!! Let the hose coil around in the bottom of the overflow tank and be sure to keep a couple of inches of coolant in the bottom of it and you got it!