Diesel pouring out of the rear - PeachParts Mercedes-Benz Forum

CnnrJ · #1 10-31-2014, 03:18 PM

Hey there, so Im in a pickle and could really use some help! I got home from work and diesel was pouring out of this hose right here, I haven't the slightest idea what it goes to or why so much diesel is pouring out. Please help!

BillGrissom · #2 10-31-2014, 03:30 PM

I had to turn my head to view. I think that drain is from the overflow hole at the diesel fill door. Check that your fill cap is on. Perhaps you overflowed several times while filling, but the bottom of the drain was plugged with under-coating, and it finally dissolved in the diesel, so years of overflow all poured out at once. Diesel evaporates very slowly.

CnnrJ · #3 10-31-2014, 03:36 PM

Sorry I uploaded that from my phone. I stuck my finger in the hole and there was what felt like rubber blocking it. When I applied pressure diesel came pouring out. I think when I filled up this morning I didn't put my cap on all the way, there was diesel all over the rear of my car. Is that just a drain hole? Should I clear the rubber out of the way?

leathermang · #4 10-31-2014, 03:43 PM

Does your car have a rubber tube going from the filling cap to the actual tank ?
Mine does...and if that is leaking then diesel would travel to that drain in the floor of the trunk.....they can split.... be knocked off... the hose clamp loosen ....

MagicBus · #5 10-31-2014, 03:46 PM

I downloaded the photo and turned it upside down for a better view. It didn't help much.

What year and model is your car? That info would help greatly. The hole you're pointing to looks like a trunk drain. Normally, water could drain out of there, but diesel shouldn't.

For no reason, I'm assuming this is a W123 sedan. I would guess that your diesel tank sprung a leak inside the trunk. The best next step would be to remove the in-trunk access panel to see if you can determine the source of the leak.

CnnrJ · #6 10-31-2014, 03:56 PM

It's an '81 300D I see the rubber drain hose that runs right besides the metal tank fill. Should I clear that hose that's pictured? It is still stopped up with the rubber under coating I just don't want to poke through it if it's directly connected to the tank

MagicBus · #7 10-31-2014, 04:14 PM

It shouldn't be directly connected to the tank. That's just a trunk water drain. I would clear it. Nothing too sharp, mind you... just in case.

I would also, then, remove the access panel in the trunk and get a flashlight.

One word of caution - diesel can soften up an asphalt driveway and cause damage (ask how I know). I would put something under there to catch the spill if I were you.

CnnrJ · #8 10-31-2014, 04:23 PM

Okay, so I cleared everything out of the trunk, wiped everything down, turned the car on and had my flashlight handy. I'm not seeing anything leak, so I'm wondering if I didn't put my gas cap on correctly, would that let fuel spew out and get into the trunk?

leathermang · #9 10-31-2014, 04:35 PM

Open the filling door....and see where the drain from there goes... if you have one....
I do not think it will drain into the trunk... probably straight to the ground..
but if you have a leak of the tube which leads to the tank inside the trunk... a flaw there will put diesel to that drain you are dealing with...
How much diesel do you have IN your tank ?

MagicBus · #10 10-31-2014, 04:35 PM

Did you notice any fuel in the trunk itself?

Did you remove the bolt-in panel separating the fuel tank from the rest of the trunk? That's the only way to be sure you see what's going on.

There should be several possible points of leaks - There's an overflow hose for when you're filling the tank and it you overfill it. That drains from the fuel filler opening through a hose (I think) in the trunk and out the bottom. Those can get clogged over time. You may be lucky and there might not be any diesel in the trunk itself. I still think you need to remove the panel to see that hose.

There's a grommet between the tank and the fuel filler opening. If you overflowed when filling, and the grommet was bad, fuel could have gotten in the trunk. Though I doubt it would be enough to cause what you're seeing.

The tank itself could be leaking from some point. Once again, you'd need to remove that panel to see where.

MagicBus · #11 10-31-2014, 04:38 PM

Quote:

Originally Posted by leathermang

Does your car have a rubber tube going from the filling cap to the actual tank ?
Mine does...and if that is leaking then diesel would travel to that drain in the floor of the trunk.....they can split.... be knocked off... the hose clamp loosen ....

Are you SURE about that? I've removed a couple of W123 diesel tanks, plastic and metal, and none of them had a rubber tube as you describe. The filler tube, as I've seen it, has always been a part of the tank itself (metal or plastic). There is a grommet between the filler tube where it exits the body by the fuel filler door. There's also the drain hose I describe above, but not a rubber tube as you describe.

I can't account for every W123 on the road, but that's how I've seen 'em.

EDIT - I just looked at the photo again (turned 180 degrees). The leak you show seems to be coming from the driver's side of the car. That would rule out (most likely) anything near the tank filler.

leathermang · #12 10-31-2014, 04:42 PM

Whatever allows the tank to be removed from the car....
somewhere there is a rubber something... either a fill tube... or a couple of connectors to a metal tube.... I think with screw up hose clamps holding them in place...
In other words.. there is some kind of flexible connection which can leak between the filling cap and the tank....

uberwasser · #13 10-31-2014, 04:43 PM

If the seal around the filler neck is old and stiff (not sealing well) fuel could definitely have leaked down the neck in to the trunk, since you said you left the cap somewhat ajar.

uberwasser · #14 10-31-2014, 04:49 PM

Quote:

Originally Posted by leathermang

Whatever allows the tank to be removed from the car....
somewhere there is a rubber something... either a fill tube... or a couple of connectors to a metal tube.... I think with screw up hose clamps holding them in place...
In other words.. there is some kind of flexible connection which can leak between the filling cap and the tank....

This is probably the tank vent, the one with the somewhat bell-shaped check valve on the end that exits under the car.

leathermang · #15 10-31-2014, 04:53 PM

I am thinking of the actual route the diesel should take to get to the tank.... how is that managed ? or sealed...?
Are there not some seals which if faulty would put the diesel into the bottom of the trunk under the fuel tank ?