Radiator cap not fit, anyone have similar problem?

[Purdy Swoft]

Originally Posted by Drive Shaft Dave

Purdy, I am having trouble picturing in my mind about the concave spacer that solders between the upper tank and radiator neck. Do you have a photo or diagram of this. Thanks , Dave

Dave, I don't have a picture. I'm sure that I have one somewhere in my stuff but it would take a massive search to find it. I don't see it listed in any of my parts books . Its been a while since I replaced a radiator cap neck on a 30-31 radiator and my description may be off , It is like a big washer that acts like a shim that would slightly raise the neck. I remember this on the last one that I did . They may not all use this part. Maybe someone else that has recently replaced a neck on a 30-31 radiator will remember this.

[Pfuerst1]

This is what I have found out trying to get the damn radiator cap to fit on my 28-29 AA:

1 The treaded portion or height of a Model A radiator neck can vary up to 1/2"
2 Reproduction/after market radiators seem to have a shorter neck than an original and are "curled over" on top rather than being a straight threaded pipe. The curled over top can be difficult to thread a correct radiator cap on.
3 The neck height on some reproduction radiator shells maybe "taller" or higher on the radiator neck than with an original shell.
4 If you look at an original gas cap there are about 1/2" of threads and a 1/4" lip below them. An original radiator cap has about 5/16" of threads and a 3/16 lip. There is also a height difference, 1 1/16" for the gas cap vs. 15/16" for the radiator cap.
If you look at a gas cap there are usually three vent slots along the beginning of the threads and a vent hole in the center of the cap.
5 There are reproduction radiator caps out there which are basically an unvented gas cap. If you look closely, the three vent slots are still there but no center hole in the top of the cap. The cap is too tall and if you try to screw in onto the radiator neck it will grab a few threads and then the lip of the cap will bottom out on the top of the radiator shell and will not seal.
6 The radiator cap may use a thin neoprene gasket that is also used in the gas cap rather than the thick gasket material that should be used in the radiator cap.

So, bottom line is that one or more of these conditions can be the problem.

[Drive Shaft Dave]

Originally Posted by Purdy Swoft

Dave, I don't have a picture. I'm sure that I have one somewhere in my stuff but it would take a massive search to find it. I don't see it listed in any of my parts books . Its been a while since I replaced a radiator cap neck on a 30-31 radiator and my description may be off , It is like a big washer that acts like a shim that would slightly raise the neck. I remember this on the last one that I did . They may not all use this part. Maybe someone else that has recently replaced a neck on a 30-31 radiator will remember this.

Thanks Purdy for the info, this is something that I would never have thought of.

[P.S.]

OK, so here is a comparison of the original radiator cap (that was drilled out for a motometer) and the Vintique repro I bought from Brattons.

Look how much taller the repro on the left is than the original on the right. Even the 'knurled' part is taller on the repro. The lip at the bottom of the original is rolled over and ends up at about the middle of the flat part of the repro.

The repro won't even begin to thread onto the radiator. The original fits perfect and bottoms out on the shell at exactly the same time it gets snug on the washer.

Any ideas?

[Pfuerst1]

The radiator cap for a 28-29 from Vinitque is basically an unvented gas cap with a wimpy neoprene gasket in it. It will not seat down and seal the radiator because it is about a 1/4" taller than a real radiator cap so it bottoms out on the radiator shell. Another good example of where reproduction parts aren't. Anyone know of a supplier that makes a real radiator cap??

[Tom Wesenberg]

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Try Bert's for the real cap. Even if it's a bit rough, at least it will fit and work. I install my rough cap for normal use. No reason to let a thief have my good cap.

[Steves46]

I know this is an old thread but I just received my A8100C Cap(not the B series) from Mikes A Fordable Parts and it will not fit and seal properly.

[BORN2L8]

When I got my new cap it wouldn't fit either. First strike for me was an older aftermarket honeycomb radiator. The neck on the radiator was too low and the rim at the shell hole wouldn't allow the cap to go in far enough to seat. I measured the distance from the radiator neck seat area to the bottom of the shell hole then transfered that measurement to the new cap. This was from the seat area on the cap down. I then measured that distance to figure how much shorter to cut the cap marking that on the outside. I used masking tape to mark the cut on both sides of the line to protect the surface. I slowly cut the new cap bottom short with a hacksaw. I cleaned up the edges with a file and sanding. Worked fine and you can't notice the cap was shortened when its on.

[Kit Foster]

I had this same problem with a restored 30 Standard Roadster I bought about 18 months ago. It came with a Ford script MotoMeter, which I disliked (ruins the looks, I think and the car never overheated), so I removed it and bought a repro cap (Macs 28-24548-1, if it matters). Would not "snick" into place and remained loose. All of the possibilities mentioned in this thread seemed plausible. I did not have complete knowledge about the parts and processes used in the restoration. The radiator mounting looked right - don't know if the radiator is original. However, I have a nearly identical unrestored car (bought the "new" roadster because I realized I would probably not live long enough nor have enough money to finish the old one), so I tried its old cap on the new car. Fits a treat, and snicks properly into place.

In comparing the two, I find the "ears" on the original cap are a thin-ish spring steel, with give to them. The repro cap has thick, immovable ears, with no give. Does anyone make repro caps with spring steel ears?