4 replies to this topic

[simon2007]

ok this is really annoying me because everytime i go round a roundabout my petrolcap leaks petrol. what is wrong? do i need a new sponge thing on inside of my petrol cap, a new petrol cap or a filter in my tank? i havnt a clue but its really costing em money now as its my daily drive. many fanx simon

Edited by simon2007, 29 April 2008 - 05:17 PM.

[DannyTip]

I got an extra seal out of an old petrol cap to get mine to seal properly.

[carl68]

The rubber seal in the cap has probably perished and cracked, best thing to do is to get a new cap, they are cheap enough from all the mini spares places.

[simon2007]

went to minimod and they got me a secondhand one that leaks even more. not very impressed.

[dklawson]

You bought a used cap. Your car already had a used cap.

You can fix this if you want to invest some time and a little money. First you have to find a U.K. source for two bits of material. You need to find a supplier for nitrile rubber sheet (a.k.a. Buna or Buna-N). Buy about 1 square foot. If you're lucky you'll find a rubber vendor in your area from whom you can buy some scraps. You want the material somewhere between 1 to 1.5 mm thick. Next find a vendor who sells Teflon in sheet form. Perhaps you'll be lucky and find one vendor who sells both. You want very thin Teflon sheet, no more than 0.010" (1/4 mm) thick.

Measure the diameter of the male projection on the bottom side of your gas cap. Measure the diameter of the tank filler neck. Use a compass to draw two concentric circles on heavy paper. The inner circle should be the OD of the cap's male projection (PLUS a millimeter or two), the outer circle should be the diameter of the filler neck (plus a millimeter or two). Staple this paper template (through the center of the inner circle) to a piece of the rubber. Use a razor blade to trim the rubber and template perimeter to match the larger circle. Then use an X-acto or similar skinny razor knife to cut away the inner circle. This will leave you with a rubber doughnut. Repeat this on another piece of rubber and finally two pieces of Teflon. You now have 4 donuts.

Remove the old seal completely from your gas cap. Fit one of your rubber doughnuts then the two Teflon washers and finally the second rubber doughnut. What you have now created is a very thick rubber seal with a Teflon thrust bearing between the layers. When you go to put this on the filler neck you may find additional pressure and torque are required to seat the cap. However, the Teflon layer will allow the two compressed rubber disks to slide relative to each other so neither one tears or distorts.

I know this sounds like a lot of work... but it isn't, and it really does work. The hardest part of the process is finding the material. I rebuilt both of my car's original gas caps this way and haven't lost a drop of fuel out of them in 5 years.