After changing out a fuel filter (inline) a few weeks ago, my '93 300D has been leaking a little bit (a very small puddle) of diesel fuel after shutdown. It was entirely dry before this. I tried reinstalling the filter a few times but the leak persisted. Suddenly, after one night of driving in the snow, the car is leaking a LOT of diesel. 1/4 of a tank (if the gauge is to be believed) last night. I've noticed that the injector return lines are wet, but could this much of a leak be all due to the braided lines? The leak is in the front of the car, roughly under the IP.

[edit] I've also noticed a pretty large amount of air in the inline fuel filter, as well as some vacuum in the fuel tank. I've tried, without success to find the tank vent.

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1992 300D 2.5T 249k - Parked with a bad transmission
1981 300SD 142k - Daily driver

Hi
I don't know the 1993 300d - but if its like my 1985 300td - there is a clear plastic filter connected to two rubber fuel hoses. One of these is a very short one leading to the injection pump. The other in the incoming fuel line from the tank.

If the rubber fuel hoses are old, I would change them both. An old hose can work fine until it is disturbed- but is too hard & stiff to make a tight seal when the new filter is put on.

A leak in these fuel hoses will have nothing to do your leaking injecteor return hoses - which will only leak while the engine is running. Of course these braided return lines should also be replaced.

A large bubble of air in the clear filter is nothing to worry about unless you also see small bubbles passing through the filter and into the injector pump. In which case you do have an air leak into the fuel system - which is likely a bad hose or leaking connection.

Good Luck,
Joseph

I've checked the rubber coming from the inline fuel filter, and it's all dry. Seeing how there is a constant leak, this is apparently coming from somewhere lower in the engine compartment... laws of gravity would dictate that it come from somewhere lower on the car than the fuel tank. I've looked under the car, but the engine trap pan is in the way... I suppose that's coming off next. Anyone have any clues as to what could suddenly be leaking so much fuel? It's a steady drip whose total volume, over time, can be measured in gallons.

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1992 300D 2.5T 249k - Parked with a bad transmission
1981 300SD 142k - Daily driver

If it's leaking that badly, it should be easy to spot. Dry off everything, start the car, get a bright flashlight and go hunting. Maybe even put it up on ramps if you think that would be helpful.

Scott

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Scott
1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)

Found the leak! It's the fuel system thermostat. I'm considering bypassing it for the time being until I can order in the repair kit.

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1992 300D 2.5T 249k - Parked with a bad transmission
1981 300SD 142k - Daily driver

Glad you found the leak. Is this on the '93? I've never heard of that part before. What does it do?

Scott

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Scott
1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)

Glad you found the leak, but I changed my fuel filter out, then a few weeks later, fuel shooting out from everywhere. I thought it was the hose leading up to that, so I replaced that, still had the problem.

Took it to a MB mechanic. Ultimately found out it was the fuel filter not screwed down REALLY tight. He torqued it so hard, the engine was moving.

jeff