Any ideas on how to handle the radiator overflow? I'm using a zero pressure cap and ran a hose into empty gal coolant jug resting on the lower radiator splash guard, but it doesn't seem to want to siphon back into the radiator.
In order to siphon, the radiator cap needs to have a gasket built in that will seal the top of the filler to the cap. I doubt a zero pressure cap has one.
Did the trucks come with one? I cant rember but I do rember replacing an AD radiator abont 1964. I was gathering corn in the corn field and backed up. A stalk of corn hit the fan and cut a 360 deg circle. Dad made me replace it by myself. The truck was abont 10-yrs old at the time.
In order for the fluid to go back into the radiator, there needs to be a vacuum created by the fluid cooling. It can't do that if the system is open, as with a zero pressure cap. It needs to have a built in gasket and valve. Normally these types of systems seem to find a happy spot as to how full the radiator needs to be without purging the extra. Mine likes it about 1 1/2 inches from the top. I don't know if you can use an overflow system on a stock radiator without a pressurized cap. Hopefully someone can chime in..Mike
Nate - What do you think? Should I keep the zero pressure cap and plug the overflow coming off the radiator neck or get a low pressure cap?
Get a low pressure cap. If your radiator/hoses/heater can't take 4 PSI you shouldn't be driving your truck anyway. And if you want to siphon the overflow back into the radiator when it cools the cap needs to seal tightly against the top of the filler. I put one on my '57 with a 7 PSI cap and a catch can. Siphon works great, keeps the radiator full and keeps air (and therefore corrosion) out of the cooling system. Maintains 185 degrees using a stock radiator in Houston's rush hour traffic with the AC on.
Well ; If it's puking coolant , you're prolly overfilling it , if you just drive it a while , it'll self level and be happy . Or , you can hang a puke tank up on the firewall high so the coolant will run back down into the radiator even with a zero pressure cap . As long as there's no plumes of steam coming out the radiator , it's not overheating ! .
Thanks Nate. I guess I was premature in my concern. The zero pressure cap seals and works. I finally had time to check things on the truck last night and the overflow "puke" tank had syphoned itself back into the radiator. Thanks to everyone for their input.
Yes & No Although it's true GMC's came with a pressurized cooling system , your Chevy's system should be able to hold 4 # without any problems .
