Mini Fuel Cap Seal Replacement

If you’ve got a first or I think even second generation BMW Mini, it’ll look something like this, you should check the fuel cap seal. It’s a pretty common failure, and beyond your fuel being able to literally evaporate away it’s also somewhat obviously a rather big safety concern. Petrol is most volatile as a gas, so it’s best not to play with fire (literally) and at least check.

Our Mini’s seal is completely shot – if you open the fuel filler flap and unscrew the cap you’ll see the black rubber seal just behind the bronze coloured lip, tucked into the plastic cap housing. As should be pretty obvious by the fact it looks like someone has gone round the whole thing with a scalpel and slashed it at fairly regular intervals, this is not much more than useless. The vapours can escape through those cracks, and worse because the nitrile rubber this is made from is clearly striff and degraded, hence the cracking, it’s also likely not making a perfect seal between the cap and the filler neck letting even more vapour out.

So, what do you do about that? You might consider just buying a new cap, and especially if the rubber line that ties the cap to the car has snapped or is completely missing, that might make sense to swap out. If that’s the case, remove any last bits of the line from the clip on the curved arm of the fuel door – it’s a little buried so a mix of smaller hands and patience is beneficial (although not required). Then clip the new line in, screw the new cap in and that’s it.

If, however, it’s only the seal itself that is worn it’s worth just replacing that rather than the whole cap and not only save yourself a bit of cash since the replacement seal is well under £10 on ebay, but it’s also pretty wasteful to throw away an otherwise functional item just because one easily replaceable part is broken.

So, how do you replace it? It’s really easy. If you’ve got a set of picks like these then you can carefully feed the pick in and under that bronze lip and lift the old seal up over the lip all the way around until it’s free. If you don’t have a pick, to be honest a butter knife would probably work about as well, or a pen knife, or if you really can’t be bothered you can just cut the old seal so it’ll slide right off. Actually, if yours is as bad as this you could probably snap the thing by hand, no tools required.

Fitting the new seal is super easy too, it helps if you’ve got any silicone based lubricant or grease – O-rings should never go on dry – but it’s so easy that it’s not exactly a problem. Just place the new seal over the green section and over the bronze lip, then gently work it over the lip evenly on both sides until it’s fully seated under the lip. 

Nice and easy right? Plus, these seals can be found for as little as £5, so to keep you save, potentially save you money on fuel, and to help pass your MOT, it’s a worthwhile thing to check and replace.