1928 -29 Radiator Cap

[Elcastor]

My radiator cap does not tighten down on the radiator threads. Is this a problem with reproduction radiator caps? Anyone else experience this problem

[Chris Haynes]

It doesn't need to be tight. It isn't a pressure system.

[BILL WILLIAMSON]

Originally Posted by Chris Haynes

It doesn't need to be tight. It isn't a pressure system.

The cap MUST be TIGHT & LEAK FREE, why else would they put a GASKET in it? Since it's NOT a pressurized system, why not just throw the cap away & use RAIN-X------------------
Bill W.

[700rpm]

Ben, yes, there are some that do not have the proper thread, and often the profile on the lower rim is wrong. The Vintique caps are like this. I got a good one from Bratton's. Unfortunately, all repros are chrome plated, not nickel. Why do they do this to us?

[Tom Wesenberg]

I've seen some original radiators with threads that are worn and don't grab more than the last 2 or 3 threads. My original 28 is somewhat worn, but still grabs enough threads to tighten and seal.

Have you inspected the cap threads or tried a good original cap?

[dave in australia]

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To further Bill's comments, if the cap is not tight, or has no gasket, then as the water expands due to heat, some drops will come out and put rusty water stains on your nice shiny paint, and windscreen. There won't be enough to block you vision, but then you still have to clean it. Not all the water will go out the drain tube, some will take the path of least resistance, or is that path of best convenience??

[Mitch//pa]

agree with post 3-4-5-6 the cap should be tight to prevent any spill over or even steam vapor to escape out the top...

[jimalabam]

Post two = left field FOWL...

[Elcastor]

My guess is that it was purchased from a very reputable dealer, as that is all I ever use. I think I will order another one, and also try screwing on an original once I get back "home".

[BILL WILLIAMSON]

In a pinch, IF you CAN'T get your cap sealed perfectly, use a REALLY BIG, tapered CORK PLUG. It would also look "COOL'' with a meat thermometer stuck in it. A friend sweated a 1/8"NPT X 1/8" ferrule adapter into his top tank & put a meat thermometer in it, for quick temp monitoring, while workin' under the hood.
Bill W.
Bill W.

[26Tguy]

I had this same problem so I cut a gasket from 1/8" rubber and added it to the cork gasket for it to seal.

However, on my repro cap, the threads were welded in on an angle that pitched the threads an 1/8" off from the outer "shell" of the cap. It's very difficult to screw on and when it is on, it is crooked. UGH! Guess I got taken on that purchase! THANKS Mac's!!!!

[Fred K-OR]

Ben, I am sure you checked this but could your radiator shell be sticking up to far and the cap hits it? I had one of my rigs do that with an aftermarket shell and I had to grind the shell down a bit.