1999 E300D W210 - Leaking gas cap problem?
 

I can't seem to stop my gas cap from leaking.

Fuel leaks and runs down the side of the quarterpanel when driving around....and with diesel at $5.35/gal in CA...every drop is important.

1st - I replaced the rubber gasket in my existing cap. No joy.

2nd - I had a spare cap from a W124. It has a cork seal, instead of rubber, like the later model cap...but seemed to fit and it's very tight. It also leaks, even though it's tight enough to leave an impression of the filler rim around the gasket.

3rd- Guess I'll have to buy a whole new cap from the dealer.....


But seems like the cap may not be the problem. ???? Perhaps something wrong in the filler neck. Can't see any dings or impressions in the rim of the filler neck.

Any ideas ??....or anyone with similar problem and a fix??

Warren C

New cap from Phil is ~$10 IIRC. I replaced mine for a different reason.

Possible your filler neck is tweaked or that the 124 cap seals differently.

That's weird and definitely sucks with diesel prices so high.

If I'm in your shoes, I don't fill it up to the brim til I get it figured out. Hopefully it is not leaking w/the tank 1/2 full.

I've no personal experience with this, but I've heard some rather nasty accounts about the filler neck being tweaked. Some fellow even had his tank replaced to fis the problem. Darned sad if that's what it comes to.

I'm with the idea of only keeping the tank around 3/4 or 1/2 and just fueling to that point when "filling up" in order to keep from sloshing out any fuel.

Preventative measures for this problem are to simply hold onto the filler nozzle and not let it hang on the filler tube when fueling. A little late for that advice now though.

If you are able to get this problem fixed, please post the fix. I have the exact same problem on my 96. Thing seems to seal good, but there is always diesel down the right rear.

Could it be that you have accidentally gotten an oil cap instead of a fuel cap? I remember reading something about that here -- the caps will interchange but not work correctly. The oil caps are usually labeled "OEL" and the fuel caps are unlabeled.

New gas (fuel) cap !
 

I bought a new cap from the dealer today....(same price as Phil w/ shipping).

The parts guy replaced the black (rubber ?) seal that came on the cap with a blue one (think he said it was neoprene)...said it was an "updated" seal.

I'll see if this is a fix and post results. Have to wash the car first.

By the way...just to note.....I've been trying various mixes of biodiesel, from B20 to B99....sometimes 50/50. Don't think this has anything to do with the leak at the filler neck though...as all the previous cap seals seem in good shape.....and the one on the w124 cap is cork???

But every time I look there's fuel standing in the crevice of the filler area underneath the filler neck and I do notice that the black drain tube in the fill area looks a bit funky....??

Does that tube drain back into the tank ...as I expect?

Car runs fine on all biodiesel mixes....and no clogged filter so far .....but keeping an eye on misc hoses/ F.I. pump area for leaks.

Warren

If Bio has been leaking down the overflow tube it may have deterioated it.

I've not had any issues with B99 in mine. I did have leaky orings shortly after the change over to ULSD occured and with old orings you might expirience the same eventually.

Filler neck is tweaked.
 

I have been down that road with new caps etc. Then spent an hour with various tools that were never designed to be placed down a fuel filler neck.

Let me see if I ever posted the solution and will put a link in. But this solved my problem well over a year ago.

http://www.peachparts.com/shopforum/showthread.php?t=174078

If your cap does not click that is clearly a problem.

Also look at the upper part of the flange inside the filler neck you will find that it is not at the same angle as the one on the bottom. The one on the bottom is wrong.

That will fix the problem. When I did this the various tools, ultra small "crowbar", talking 6" one, I clamped a pair of vise grips on them. Do not want to drop anything into the tank.

Please post the "successful" repair.

No, that drain does not go back to the tank, it lets go under the car. You would not want rainwater that gets blown past the fuel door going in the tank and that is there primarily to prevent water from pooling, but when you overfill or splash fuel it will also go down there. Maybe your drain is clogged and when you see "fuel" down the side of your car it is really just water that pooled washed out all of the crud out of there when you turned left. Did you notice the stains after it rained? Make sure that little drain is clear...check it and flush it out if need be. It may be the cause of your staining.

Don't think so
 

I live in N. CA where it hasn't rained for over a month ...and the stains down the side of the quarter panel are greasy and collect dirt......definitely fuel. Also I can see the amber color of the fuel in the crevice below the filler neck.

The outer edge of the drain tube looks swollen up a bit (from biodiesel ???) around the edges ...creating a raised lip around the tube so that anything spilled in there doesn't all drain out...

Warren C.

Is the drain clogged or clear? Try pouring some water in there and see how it flows. Maybe it is clogged and backs up from expansion once you are underway and spills out the side. Do you have a feeling for how much fuel you're losing? Is it just a little streak or a huge stain?

Don't know if it's clogged...what's the best way to check it out?

Big stain down the quarter panel.

WC

Like I said above, try pouring some water in it and see if it drains out the bottom. If not you can snake a coat hanger or similar wire carefully down it and clean it out.

Why not check the fuel filler neck. I was abosultely convinced mine was fine. Well it was not. If you check my original post the time from discovery of the problem, to fixed and test driven, back here and posted was less than an hour. I suffered with this for a couple of years and this could be done this afternoon.

What happens is over time the fuel nozzle bends the fuel filler neck down on the inside. Just to humor ourselves please take a look compairing the upper tab to the lower tab.

Does your fuel cap click when you install it?

Mine was deflected less than 1/8", but we are talking gaskets sealing here and that is all it takes for the giant splash of fuel down the side.

Please take the time for a thorough comparision of the two tabs inside the fuel filler neck.