My brother and I are trying to locate a fuel leak in his '99 E300D. The car was parked overnight on an incline with the nose downhill, and a spot of fuel about 18 in. diameter formed under the engine. Fuel had evidently accumulated and spilled from the protective plate because of the incline. It is very difficult to see where the leak originates and he is going to remove the washer reservoir for a better look.

It looks as if the leak is in the area of the clear fuel lines above the IP. My questions are:

Is this a common place for leaks?

Do these lines get brittle and crack?

One thread said that the O-rings where these lines attach are a common problem. How difficult is it to replace the O-rings without removing the aluminum manifold?

Is there another place around the IP that is prone to leak?

Thanks,

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Bruce

73 220D (never left Germany)
81 300D (totaled)
84 300D (Purchased '03, sold '17)
85 300SD (purchased 10/01/03)

It is a VERY common place for leaks on these cars. The lines do discolor and the O rings do leak, I don't believe the lines cracking is your problem. The most common leak source is the O ring on any of the clear lines. Some of the lines can be replaced with the IM in place. Replace the ones you can and see if that solves your problem. If not the IM isn't that hard to R+R. Don't forget; there is an O ring behind the shut-off valve and another on the pre-filter. The one on the pre-filter isn't a standard size O ring so don't try to "make one fit". Buy the right one from MB. That $2 O ring cost me $700 at my FORMER indy's.

Sounds like you have a relatively common problem for these cars. If you can, just replace all the clear lines and O rings at the same time. That should solve your problem.

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Muleears
'07 E320 Bluetec 133K my DD
'04 Jaguar XJ8 VDP, 34K
'10 Hyundai Accent 60K Grocery Getter
'02 VW Golf soon to be on the road again
'97 E300 Diesel Son's DD
'61 VERY tolerant wife

Hampton Roads, VA USA

Gone but not forgotten:
'67 250S 95K
'86 300SDL
'87 300D Turbo, 364K! R.I.P.
'98 E300 Turbodiesel, 213K
'02 S420, 164K
'01 Prius 138K

You should also check the top of the IP around the area of the delivery valves. I had a leak similar to yours, and it turned out to be in that area. I had to replace the "O" rings and crush washers. The leak would occur while the engine was running, but was so slight that it would run along the top of the IP, and then drip into the belly pan below. It would collect there, and if the car was parked at an angle like yours, I would end up with a small sized leak under the car. You can use brake cleaner, or carb. cleaner, spray the top of the IP, and wipe it dry. Then start your engine, and watch carefully for leaks around the delivery valve area. Mine was so slight, that it was hard to see, and I had to tell by running my finger along the top of the IP. Good luck!

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96 E300d

The fuel shut off valve is also a common failure. i had it fail on me and I had a nice sized puddle under the engine after parking it overnight.

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Ed
-1984 Mercedes 190D 2.2 5-speed gray market(bought@30,000 miles) (Sold back to original owner@170,000 miles)
-1999 Mercedes E300DT (245,000 miles)
-1999 Mercedes S500 Grand Edition (80,000 miles)