Hi all, On my 62 c10 with sbc 350 my coolant is boiling over around the fill cap of the 2 year old radiator. It bypasses the overflow tank. All the while I'm watching the temp guage and it doesn't increase at all. Normal operating temp. I can't remember exactly, but it's either a 13 or 16lb cap. Any ideas why its boiling over but temp not rising? Guage is a cheaper unit, but it seems to be working correctly. Any help is appreciated. Adam
Do you fill the radiator all the way to the top when it's cold? Does the cap have the extra rubber seal around the outer rim, on the bottom, that is needed to work with a recovery tank?
Will have to check all that at lunch. Drove it to work today and all this steam started coming frow under all sides of hood. Was kinda embarrassing but thats life! Adam
I treat the older radiators like we always did before they invented coolant recovery tanks...I fill them so the tank is about half full when it's cold, then when the coolant expands it will not quite come up to the cap. You might also have a cracked flange where the cap goes on.
Are the hoses to and from the overflow tank clogged or crimped? A hand held non-contact infrared thermometer can be useful in determining whether your gauge is accurate, among other things.
Filled to top of top row to allow for expansion. Maybe I filled a little too high. Still gonna check that cap and make sure its right. New radiator didn't come with a cap, So I probably just grabbed first one I came to and didn't look for extra gasket. Adam
Look at it this way, if everything is operating normally and it overheats the coolant should come out the overflow. It should not be spewing at the cap! Either the cap is bad, the flange on the radiator fill is damaged, or the hose is plugged leaving the coolant no place else to go. Get a new closed system radiator cap, check the overflow hose, make sure the hose is immersed in coolant in the tank (or attaches to the tank near the bottom), and make sure there is an overflow hose coming off the top of the tank and directing the overflow to the ground. When the engine is stone cold the radiator should be full and the overflow bottle should have enough coolant in it to cover the hose going to the radiator. ~Alden
Haven't checked that cap yet, but you seem to be describing all that I've checked. I'm betting money I don't have the closed system cap. Adam
I have a 16lb cap and there are two gaskets. One at the plate at bottom of spring where it would mate inside filler neck, and one that is up in the cap where it mates to filler flange. The coolant level is not visible right now with the engine cold. Which cap is this? Not sure I'm understanding.
After some thinking on it, am I right to assume the open cap is the one that only has one seal with no spring? And the closed one has the spring that seals off radiator core in bottom of filler neck. The open cap is what I need if I just run the overflow down to ground? Thanks for helping me understand this. Adam
They all have the spring and seal at the bottom, and the closed system caps also have a rubber seal at the top, so it will seal the very top of the radiator opening. This lets it suck the coolant from the recovery tank, back into the radiator, as it cools.
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