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Old 07-31-1999, 09:18 PM
mbz owner
Posts: n/a

My 126 300SD has developed some sort of fuel leak. I can smell a light odor of raw diesel in the passenger compartment when driving, seems worse towards the back. It doesn't look like anything in the engine is leaking and smell is stronger in the trunk. What could be the culprit in the fuel tank area?

Old 08-01-1999, 01:02 AM
Robert W. Roe's Avatar
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Join Date: May 1999
Location: Lehigh Valley PA
Posts: 1,321
It could be either a leaky fuel tank or one of the many pipes and hoses that connect to the tank itself. The fuel tank of the 126 SD is behind the back seat.

If you search the archives for "fuel leak" or "fuel smell" you should get some matches.

On my '83 SD the hose adjacent to the fuel filler had pulled off. I'm surmising that at least once during filling the tank some excess fuel ran out and into the trunk rather than through this hose and onto the ground.

To get to this hose I had to remove the side and front trunk liners and remove several screws from the steel bulkhead that separates the trunk area from the fuel tank. I had to climb into the trunk to get sufficient leverage to push the hose back on. There are lots of vent lines and fuel return lines that could be the culprit also. My leak was bad enough to soak the passenger side trunk liner with diesel fuel.

Robert W. Roe
1984 300SD 164K mi

[This message has been edited by Robert W. Roe (edited 08-01-1999).]
Old 08-01-1999, 01:00 PM
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Join Date: Jul 1999
Posts: 239
Please take care of this problem ASAP as diesel fumes is not the healthiest thing to be breathing...

I recently experienced a major leak into the trunk and to my astonsihment discovered a ruptured tank that was expoxied. Bad move by the previous owner and the shop that did the work. (A new tank was installed immediately) After repeated washing of the wheel well liners and carpeting at the car wash, the faint diesel odor is still present.
I still haven't reinstalled them after nearly six months of airing them out.

Any suggestions on floor and side well liner decontamination ?
Old 08-07-1999, 10:39 PM
mbz owner
Posts: n/a

After several weeks, I think I have solved this problem. Few weeks ago, I think I installed fuel cap somewhat loose and allowed diesel to spill via the drain hose into the passenger compartment. The trunk liners were soaked and still do smell of diesel...

Only problem now is how to air them out.

PS I think I must have a leak in that overflow hose??

Old 08-08-1999, 11:36 AM
Robert W. Roe's Avatar
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Join Date: May 1999
Location: Lehigh Valley PA
Posts: 1,321
I think that you are going to have to find a product that will dissolve the diesel fuel, and wash it off. I don't believe that diesel fuel will ever evaporate fully; rather it would thicken as the lighter componenets evaporate, leaving an oily and still-smelly residue.

I've been hesitant to suggest what I am about to, primarily due to the danger of fire and/or explosion. Unfortunately, the only things that I can think of that would dissolve diesel fuel are both flammable and not good for you: something akin to gasoline or petroleum naptha.

I never tried it for this purpose, but 3M makes a product called adhesive remover that is 100% naptha. Using enough of this (at about $6 a can) may just rinse off all the diesel fuel from your trunk liners (if it doesn't dissolve them) as well as removing any protective wax from the paint inside the trunk. Make sure you can leave the trunk open until you smell no trace of solvent.

I would read label directions carefully, and not attempt this in a garage, or near other people, sources of ignition, smokers, etc.

Robert W. Roe
1984 300SD 165K miles

Old 08-08-1999, 01:16 PM
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Join Date: Jul 1999
Posts: 239
You may want to try one thing before using solvant as a last resort -

I removed the stiff side liners, floor carpet and the bulkhead carpet (peel it off the adhesive - a lot easier to clean) then took them to the car wash and blasted them after soaking in some strong detergent. The stiff side liners are tricky since they have a molded solid backing. I worked the spray to push the rinse along the surface, going from center to the edges. It is possible to get most of the stuff pushed off.
As for the carpets, since they can be blasted through the fabric, it's easier to clean more thoroughly.
Afterwards, the liners were aired out for several weeks, sometimes in the sun.
The odor is gone but it took plenty of quarters for about 5-6 rinse cycles.
I was lucky the fumes didn't get into the rear seat cusions....
Don't forget to thoroughly clean the metal surfaces and soak up any fuel that accumulated in nooks and crannies..
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