W108 Fuel Filler Neck Vent Hoses

[karshack]

Just thought I would chime in with my replacement of the original cloth covered hose sections. As you will remember there are two hose sections that attach to the the filler neck and metal fuel lines to the vent compensation tank.

It took me a few months to realize that the cloth covered hoses where reeking of gasoline and were constantly damp to the touch.

I replaced the original hoses with Tygon F-4040-A hose that is rated for fuel use. The size I'm using is 1/8" ID x 1/4" OD Usually sold by the foot, you only need about 7 inches total for both hose sections. Always much better to have more hose than needed. The wall thickness makes it a little stiff for the necessary bends in the short section. That is solved by placing both new lengths of hose into a cup of very hot water for a few minutes, then wiggling the hose ends over the tip of a medium philip-head screwdriver.

The Tygon hose is a yellow color, and transparent. I plan on replacing the hose in 3-5 years. Could it last longer? Very probably. But degradation will occur sooner rather than later because of the amount of ethanol in today's gasoline. No reason to test the failure limit. And it will be easy to see and feel any leaks and cracks because of it's transparency and not being covered by cloth braiding.

Oh, and I'd always suggest using a simple block of wood to keep the fuel filler door open. Don't use your gas cap!

Good luck

[Tomguy]

Did you also replace the fabric lines in the trunk where those connect to the vapor canister, behind the spare tire, or did you not have any leaks there? My trunk smelled like gas until I replaced those (ironically the ones "Outside" the trunk by the filler neck were fine). I just used EFI-rated fuel hose when I did it.

I never had an issue using the gas cap to hold the door open, but my cap was a different style. Yours almost looks like it might be from a later model year MB? Mine was a similar style to the oil cap.

[craftysince86]

Originally Posted by Tomguy

Did you also replace the fabric lines in the trunk where those connect to the vapor canister, behind the spare tire, or did you not have any leaks there? My trunk smelled like gas until I replaced those (ironically the ones "Outside" the trunk by the filler neck were fine). I just used EFI-rated fuel hose when I did it.

I never had an issue using the gas cap to hold the door open, but my cap was a different style. Yours almost looks like it might be from a later model year MB? Mine was a similar style to the oil cap.

Same here, but my gas cap doesn't have a lock on it. Do the cars equipped with locking gas caps have a non locking gas door?

[DieselPaul]

This replacement has made a difference on a lot of my Benzes of a similar vintage, I buy the cloth covered hose from the dealer for a more factory look, but your hose is probably of much higher quality.

[karshack]

Tomguy - Yes, I did check the hoses to the compensation tank in the trunk. That was the very first thing I checked when trying to figure out the causes of the trunk's fuel funk. Those hoses are not weeping or leaking - no odors at all coming from the hoses or the tank.

The reason I suggest using a little block of wood to hold the filler door open for non-gas station activity is because (1) those 2 door springs are strong and will wear out your hand/arm faster than you imagined, and (2) using the gas cap to hold it open means the filler pipe is now open stuffing your face and environment with gas fumes and allowing you to drop anything down into the gas tank.

I just got a replacement Meyle gas cap - plain without a lock. I had failed to notice that my locking gas cap did not have a rubber gasket and was a major culprit in contributing to the fuel funk.

Does anyone know why MB designed the trunk shell so that the slightest dribble of fuel out of the filler neck would immediately get into the trunk and then the passenger area because of the many pre-stamped holes in the hat shelf/trunk sheet metal? Seems to be a very poor design, or a bad engineering compromise.

Thanks for the responses!

[karshack]

My Mercedes Parts Catalog "A" 12-110 (1965) shows a locking gas cap [Table 24, Page 128]. The car only came to me with 2 keys - and the non-ignition key does not fit the cap lock so it's just constantly unlocked.

Remember, I'm just talking about the gas cap, not the gas filler door. I don't know if any W108 model had a locking gas filler door. We used to have 1972 280SE and that didn't have a gas filler door lock.

That reminds me, I need to post some pix of a work-around for W108 gas station fill-up problems with with fuel pump emission/vapor recapture nozzles.

[Tomguy]

My 108 had a locking gas door - locked with the vacuum locks whenever the driver's door was locked, just like the rest; downside being it requires constant vac to stay locked so if the lock rubbers are leaky, it doesn't lock. I didn't know that MB made cars without this option, so I almost wonder if you've had cars where it was just removed due to the leaks?

I didn't get what you were saying with using wood instead of the gas cap for work in that area. Yes, that makes sense! I thought you meant during fill-ups making me wonder where you put the gas cap When I would work on mine, I just used a spare cap I had from a junkyard car.