Lost gas cap

[Jowe]

Earlier this ear I bought an original, very expensive , gas cap. One notice I made was that the cork gasket was very thin though. However, I fitted the cap on the car and felt very satisfied with this new gem . When I the other day took a short drive in the city, an individual knocked on my passenger door at a red light and told me that I was running without the gas gap and petrol was pouring out during my driving . I returned back home the same way, looking for the lost cap. Eventually, I found it in a roundabout close to my home - smashed of course , as seen on the pic below.

Now I wonder if I may have fitted the cap in a wrong way, i.e. not turning it hard enough or that the thin cork gasket could have been a cause? Anyone who has any clue on this?

[Rolf-Dieter ✝︎]

Sorry to read about your bad luck. I always spin my gas cup before I leave the filling station to make absolutely sure she is tight. Give the next one good tests to make sure (as I know you will) it does not happen again.

Dieter

[Paul & Dolly]

Hi Jowe,

I am sorry for you, they are not cheap, & there have been a few instances on this site , similar to yours.

I have found that a smear of vasoline on the cork gaskett helps the cap to seat, rotate, and lock properly.
Also check that the rubber grommet (gas tank filler to body) is not fouling the cap and hence preventing it rotating properly.

Best wishes
Paul

[Jowe]

Thanks Dieter and Paul. I now use my old cap (which has worked perfect all years) and started to fill the pig with dimes for a new one, again

[RAY]

Hi Johan,
I did exactly the same thing but was very fortunate because i had stopped to fill up with petrol and only drove a few hundred yards home to wash the car and noticed the cap was loose. I still remember now thinking how lucky i was.
Just prior to that i had noticed the cork had stretched and was no longer a good fit and i think that may have caused the cap not to seat properly and therefore lock correctly. I imeadiatly replaced the cork with rubber and have not had a problem since but always check it 2 or 3 times that the cap spins freely and i can't pull it off before i pull away.
Best wishes
Ray

[mbzse]

.../...I wonder if I may have fitted the cap in a wrong way, i.e. not turning it hard enough.../...

The two tabs "wings" on the cap grab the end of the filler neck (tube) which is swaged to a wedge ("ramp") shape, this ends with a slight cutout.
That is the secure, closed position for the cap (spring loaded).
I borrow a picture [from Flavio "watson" ]  to show the filler neck detail

One must twist the filler cap until the tabs go into that cutout (almost half a turn), it can be felt quite distinctively (IMHO)
and the twist should not go easy or have any free play at the end.

The metal in the cap is pot metal and (unfortunately) it wears so the free spin/locking function (with the key) of the cap may become dodgy

Achim has given some tips see
https://www.sl113.org/forums/index.php?topic=16809.msg117657#msg117657

[114015]

Hello Johan,

Very sad to hear about the loss of your (new) gas cap.
Now that you found it again, it's only good for parts.

As to your old gas cap (or perhaps once a new one coming along in the future),
always make sure that the gas cap's bayonet catch is properly locked.    Only then lock it with the key ! That's the solution to the problem of loosing gas caps while driving.

Second: replace that old (or new) cork seal/gasket with a modern type rubber seal/gasket,
the one with the W140 parts number (A140 471 00 79) and grease the gasket properly.
You should never face problems again.

You can also disassemble your old gas cap (see the Wiki or the BBB group 47 on how to do that) and get the outer chromed cap half freshly rechromed.
That's what I did.

Good luck!

Achim
(gascapaficionado)