Packard Forum Index » Pre-War (1899-1942)

I just pulled and inspected my water pump and flushed the radiator and engine block. Putting things back together I realized that I need to know more about the radiator cap itself. Not the figure on the top but what the cap looks like underneath. I have two caps and they both are different. The one I'm guessing is more correct is configured in the following way. If you turn the cap over and remove the central bolt, next comes the metal piece with the three stubs that fit into the slots in the top of the radiator. Next is a fiberous gasket, thin, almost like very firm paper. Finally there is a metal (brass ?) convex washer. It seems like the metal washer pushing the gasket onto the ring of the radiator opening forms the seal. But, inside the radiator opening is the top of an overflow tube that sits far enough below the gasket that nothing appears to seal it off. So my questions are:
1. What is the underside of the cap supposed to be configured like?
2. Is this a sealed system?

Nothing should seal off either end of the overflow tube, that would negate its function - it's there to allow excess coolant to drain away should it rise to that point. Obviously it's preferable to have excess coolant drain away thru the tube to beneath the car than to have it overflow the top of the radiator onto the paint and plating.

Your system is a simple gravity system, pressurized systems on Packard began about 1941 or so - your is just open to the atmosphere. Other than ornamentation the function of the cap is simply to prevent coolant sloshing or overflow if boiling and to keep debris out of the system.

I guess you want some pictures.

Here are two. The metal Belleville washer is what keeps the thing from turning around on the road.

So here you see the sealing fiber washer in the first picture. In the second you can faintly see the belleville washer which installed concave (or curving down).

Incidentally, the overflow tube should not be near the top of the radiator neck. If it is, you will get spray onto the hood. Also, the adequate coolant level is high enough to cover the core tubes. Too high and it will spray.

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Owen and Tim, thank you both for taking the time to get me the information and the pictures. Very helpful and clarifying.

Bill