Fuel cap rubber rejuvenation

[Duane Bolin]

I have a thermos style fuel cap that is not as tight as it was when new and I have heard that soaking in MEK or Lacquer thinner may help to swell the rubber and rejuvenate the rubber. Does anyone have experience with this procedure and if so which solvent did you use and how long did you let the fuel cap soak.

Thanks,
Duane

[Michael Bryant]

I have not done the procedure, but have seen it here and in the Tips pages.

Here, just do a search. I'd use MEK and thinner as search terms.

For the Tips pages, go to the home page and click on the Technical tab, then Comanche Tips, then Click Here to Read Online. Not as easy to find specific things, but it is searchable. I selected the Fuel System, then searched for both thinner and MEK and found reference to MEK for fuel cap repair.

[Donald Shaffer]

I do know that MEK will breakdown elastomers in rubber. I used to use it a long time ago until it was banned from use in semiconductor cleaning applications once it was proven to be a carcinogen. It would make latex gloves turn hard. No way I would use that on my plane.

[LeWayne Garrison]

I have done this with MEK and it works very well. Leave them soak for a couple of hours minimum (MEK will probably evaporate by then). Each time you do this, though, it does less good. Eventually you will have to replace. And yes MEK is a known carcinogen, but so is almost every other chemical. Use nitrile gloves and avoid ingestion.

[JIMICS2452]

MEK will attack the rubber and eventually make it too hard to rejuvenate. Lacquer thinner works better in the long term.