Fuel cap leak

[jeff10049]

So my fuel cap leaks down the side of the car and leaves a nice stain on the new paint.
I cleaned it off with rubbing compound but would like to stop this from happening every time the car is driven.

To make matters worse some was leaking past the filler neck grommit into the boot without me knowing and ate the paint off my freshly painted spare wheel and boot floor I thought most 2k paints were fuel resistant but I guess fairly new paint with fuel sitting on it long term will fail.

The cap is vented and I think its the vent hole that leaks fuel as the gasket seems fine cap is new. The tank also has a vent, is there any reason to have a vented cap with a vented tank? I would like to block off the vent holes in the cap.

Anyone else have this leak problem? suggestions?

Jeff

[MiniDave]

Where does the fuel tank vent go? Is this a late model car with a charcoal canister?

[MPlayle]

Also, make sure the tank vent is not clogged/blocked.  When filling the tank, leave a little room for expansion as well.  That should give enough room to minimize any sloshing from driving being "burped" out the tank vent and/or cap vent.

Most of the "experts" seem to agree that you should not fill into the neck of the tank, but stop just before the fuel reaches the tank neck.

[MiniDave]

Yep, I made the mistake of filling up the tank on my Clubby one morning then parked it on the curb while I worked on other cars in the shop......the back was downhill and it got hot that day. I came out a few hours later to see gas dribbling down the side of the car - the paint was bubbling up there - it still looks like shit.

[MPlayle]

Van and Pickup tanks are not vented, so even more prone to dribbles when full and let sit in warm sunshine.

[MiniDave]

Yep, I'm well aware, it was the combination of being ass down and parking in the hot sun that did it.....

You don't want to overfill a modern car either, cause you don't want to introduce liquid fuel into the charcoal canister....

[jeff10049]

Dave, my tank vent is just a small hose window washer size that comes off the top of the tank and is routed out of the boot floor. Seems like that would be enough of a vent not sure I need the cap vent also.

The car was/is doing this at 3/4 - 1/2 tank only when driving I have never filled it up to the neck. Im lucky enough that it has not bubbled or damaged the paint on the car yet Id like to keep it that way. The boot floor is bad enough.

I'm still thinking I should block the vented cap holes and just have the tank vent unless someone knows of a reason I should have a vented cap and tank. I guess this was not much of a concern back when the cars were made? seems like there must of been lots of minis running around with no paint below the gas cap considering they were painted with lacquer back in 60.

Mplayle, the vent is open I checked it.

Jeff

[MtyMous]

So is there an over-engineered solution to this yet? haha. I'm only half joking though. I'd like to completely eliminate the chance of fuel spills on Tink and I'm willing to do something slightly over the top to ensure it doesn't happen.

I would think a good sealed cap should do the trick. Especially if the tank already has a top mounted vent like mine does. I want it to seal well and fit under my monza cap.

[Willie_B]

Not my fix.  The extra rubber keeps the sloshing gas away from the gas cap so it does not leak out. Just make sure the rubber you cut the piece from is gas friendly.

[94touring]

I'd buy a new cap with a new rubber seal assuming the seal is failing or just get a new non vented cap.  You have the tank vent which is enough.  As far as paint goes, fuel shouldn't be eating it up.  Perhaps if it pools up and sits long enough it will though. 

[jeff10049]

Thats what happened Dan, the paint on the side of the car is fine its in the boot where it sat around the spare wheel that it ate the boot and wheel paint. My cap is the new polished one so i'm going to try blocking the vent holes with a little bit of fuel tank sealer. The only non vented caps I found fit a different filler neck or were locking do you sell a non vented/non locking cap for the early filler neck?

Jeff

[94touring]

I don't.  Keep the paint below the cap freshly waxed in the meantime.  Must be really gushing out to pool up.  Somewhat surprising to me. 

[MPlayle]

Could there be a leak around the sender unit?

[94touring]

I was wondering about a leak too.  Half full it should be virtually impossible to leak out of the cap.  Unless you're doing barrel rolls in it!

[jeff10049]

I thought that too but its been sitting two weeks almost full and dry as a bone around the sender, no barrel rolls not even hard driving as I just got the car together only about 50 miles on it so far. 

Update on problem I think the gasket on the cap may be squeezing out of place when fully tightened I may glue it to the cap to help keep it in place I can't see it leaking as bad as it is out of the little vent holes.

[geoO]

Here's what solved the issue for me, after a suggestion from another Mini owner. I made two washer shaped disks out of nominal 1/16" thick Buna-N (Nitrile) rubber sheet and two disks out of thin (0.005"-0.010") Teflon sheet.  I placed one Buna disk on the cap, then the two Teflon disks and finally the second Buna disk.  This created roughly 1/8" thick seal with a lot of downward pressure against the filler neck.  However, the paired Teflon disks act like thrust washers which allow the two rubber seals to slide/rotate relative to each other so the rubber doesn't twist or tear when tightening the cap. 

[94touring]

Here's what solved the issue for me, after a suggestion from another Mini owner. I made two washer shaped disks out of nominal 1/16" thick Buna-N (Nitrile) rubber sheet and two disks out of thin (0.005"-0.010") Teflon sheet.  I placed one Buna disk on the cap, then the two Teflon disks and finally the second Buna disk.  This created roughly 1/8" thick seal with a lot of downward pressure against the filler neck.  However, the paired Teflon disks act like thrust washers which allow the two rubber seals to slide/rotate relative to each other so the rubber doesn't twist or tear when tightening the cap.

Do you have pics of this? 

[jeff10049]

That could work my problem was the gasket getting twisted out when tightening the cap I glued the gasket to the cap and carefully tightened it no more leak. The Teflon would be even better as the single rubber gasket does bind on the filler neck when turning.

[MtyMous]

I second what Dan said. I want to get this right before I even put any gas in the car. Can't be ruining this fancy paint job Dan gave me. lol

[94touring]

Your paint won't peel due to fuel, though I'm tempted to test out fuel sitting on the paint I use for extended periods of time.  I'd like pics for a diy link, plus my fuel leaks too!

[94touring]

Also fiy Cameron my blue mini was painted with Dupont croma 12+ years ago, sat unattended collecting dust inside and outside, and shows no sign of failure. 

[MtyMous]

Well that certainly makes me feel better about it all. But no one likes to waste gas. lol. If you get that DIY link up, I'll be on it to make my own quickly. I've got a monza style cap in the garage waiting to go on (Gotta subdue the chrome first) but that means my choices on fuel caps are limited to the ones that fit under it. Gotta have a good seal on it.

[jeff10049]

my paint was fine where the fuel just ran down it. Only got screwed where it sat in a puddle on the boot floor. That might have survived had the paint not been so new. I used diamont a top shelf product.

jeff