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TR4/4A TR4 Gas Cap

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Miles64

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I have had a 64 TR 4 about four months and would like to know if there is a gasket of some kind that fits inside the gas filler cap. My other LBC is a 1952 MG TD and it has a cork seal that fits under the rim of the cap. I have looked in the Moss catalogue, but did not see a part.
Any help would be appreciated.
 
There should be a groove (about 1/8" wide) in the lower half of the cap that the springy inner cap fit against/into. That groove would have had a rubber seal that may have dried out, shrunk or plain disappeared.

I renewed mine with a piece of square-profile o-ring. The ring was too big a diameter so I just cut it down to a suitable length and jammed it into that groove. I think I used a leftover gasket from when I still had the canister oil filter though any old o-ring of the right profile should suit. It doesn't get soaked with fuel so I don't think it has to be fuel-proof to do the job of holding in vapors and keeping the cap tight.
 
Moss sells this part# 680-575 for $5.55 and TRF sells part 650247 for $5.50 but the oil filter o-ring works just as good and there are usually extras that come with the filter. Much easier to clip and fit a ring than changing the entire part too.
 
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Moss sells this part# 680-575 for $5.55

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Thanks for that part number (and the tip on making one). I have been looking for something like that for years. My TR3 seems to smell like gas when in the garage and I have not been able to find a leak. So I have suspected the cap for years. The question I have is how did you find this part (number). The cataloge does not seem to show this part in the diagram. Doing a search of the PDF catalog does bring it up though. What am I doing wrong when looking for this sort of part.
 
I'm not sure that 680-575 is the same part I was referring to... Miles was asking about a gasket that fits inside the gas cap which I took to be the one the inner lip of the cap presses against. That part is the same on TR3s and 4s whether they have the later one-piece gas cap (integral neck) or earlier multi piece gas cap (threaded).

680-575 appears to be unique to the later cap and seals the neck to the body... but then I haven't actually ordered one to see just what is supplied nor have I taken my TR4 cap off to see what is under there.
 
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I'm not sure that 680-575 is the same part I was referring to... 680-575 appears to be unique to the later cap and seals the neck to the body... but then I haven't actually ordered one to see just what is supplied nor have I taken my TR4 cap off to see what is under there.

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That is correct. I ordered one of those for my TR4A and it is a giant grommet as best I can describe it with words. I am trying to find the one under the cap or the pressure one as you describe it. I looked under my spare cap and it seems to be some sort of fibre one (though over the years a lot of materials can end up looking like fibre. So who knows what it was to begine with.

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