Dear Geniuses,

My 1984 300D has leaked lots of fuel into the trunk. I am completely clueless as to why. It leaked gallons, not just little bits. It all started one day when I topped off the tank at the gas station. I parked the car, and then a few hours later, I noticed gallons of fuel leaking out of the vents in the trunk wells.

Since then, I've let the car sit. Now that I'm getting back into fixing it again, I opened the trunk and noticed that the breather tube next to the filler was disconnected and the cap to the filler neck is also somewhat old.

Do I have a leak in the tank that appears to be very sturdy? Or do I have a leak in a line somewhere? Mind you, the fuel was only leaking from the trunk and no where else.

Any help you can provide is extremely appreciated.

I think you're on the right track. I doubt the tank itself is at fault. Check the line that runs from the filler well area down to the ground. Re-attach the line. Get a new filler neck gasket and gasket for the tank cap.

Remove the rear divider in the trunk, its held on with 8mm screws. You'll then get a good look at the tank and see if fuel is coming off the top of it somehow from the sender area (the sender is underneath the first aid kit).

dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

The top of the tank looks fine. The sender seems to be in tact (thank goodness!) I think the issues are with the fuel lines that go from the bottom of the tank and to the engine. I'm just very confused as to how it got in the tank. I would say I lost about 8 gallons of fuel that day.

Certainly take care of those bottom fuel lines. 8 gallons is a lot of fuel!

Is the rest of the car rusty in such a way that would make you suspect a fault in the tank due to rust?

Here's a pictorial of replacing the fuel lines:
http://www.dieselgiant.com/mercedesfuelhoseinstall.htm

Heres a pictorial of removing the tank:
http://www.peachparts.com/Wikka/W123FuelTank

dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

There isn't really any rust on the car that would lead the fuel tank to rust. Do you think the lower fuel lines could cause fuel to get into the trunk?

Maybe if they were leaking right at the top and wind blew it back into the trunk? But that is sketchy at best.

If your lower fuel lines are leaking it's time to change them anyways. You'll need to drain the tank to do that. To remove the tank after draining is not that much more work.

If I were in your shoes, I would remove the tank (and all the trunk liners) for a full inspection. I'd replace:

- tank screen gasket
- lower fuel lines
- tank neck gasket
- tank cap gasket

The more I ponder - I cant think of a way 8 gallons can get in your trunk without a leak.

dd

__________________
-------------------------------
'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

Thanks for your help! I'll be getting in there and replacing fuel lines soon.

I would question 8 gallons. Is that an estimate based on what?

I bet its just the rubber lines running from the filler to the tank. Also in some models there is a drain tube that runs from the filler neck door through the trunk to the ground. If this little tube perishes the fuel sloshed around the filler goes into the trunk.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.