bio and fuel filler neck seal grommet - PeachParts Mercedes-Benz Forum

allenying · #1 05-08-2016, 10:19 PM

hi,
5 months ago i replaced my fuel filler neck seal grommet with the standard oem rubber one. i knew bio would eat at it, but i didn't think after only 5 months, 10 fills, it would be melting away, as pictured, and when i wipe excess fuel off as i always do, the melted rubber gets on the paper towel and gets on anything it touches.

i'm pretty sure there isn't a synthetic viton type part that can be used for this, is there? is anyone else experiencing this, or have any solution ideas?

i'm always pretty careful about wiping up excess fuel, with rags and paper towel at the biodiesel pump i go to.

thanks!

funola · #2 05-08-2016, 10:53 PM

Buy a new one, clean de-grease spray it with epoxy paint before install. Just an idea. I have no idea if it'll work but I have a feeling it may.

mach4 · #3 05-09-2016, 01:35 PM

The obvious answer is to use real diesel, but barring that you might try polyurethane. If I suddenly found myself in a situation where biodiesel was the only available fuel (and living in CA, that's unfortunately not beyond the realm of possibility) I would try some two-part polyurethane brushable mold material EZ-Mix® 40 Brushable Urethane Rubber Compound In a molding application you'd use a mold release agent, but as a coating, urethane is a pretty effective adhering and should hold up pretty well as a barrier.

tjts1 · #4 05-10-2016, 12:08 PM

WOW I'm glad we have renewable diesel instead of biodiesel in California. That can't be normal even for biodiesel. Imagine what it's doing to the inside of your fuel lines.

allenying · #5 05-10-2016, 01:39 PM

i guess that's why they say to change fuel lines to synthetic rubber, bio safe, or viton lines. it would be great to have domestically made renewable diesel available in ny.

where is that chart from mach4?

thanks,

bricktron · #6 05-16-2016, 02:08 AM

i have the same problem to a lesser degree. idea: how about replacing the rubber with a strip of rag, tied around the fill tube, swapped out as often as warranted?

Murkybenz · #7 06-04-2016, 01:45 PM

Get a motorcycle inner tube and cut a flat section out around seven by four inches , cut a hole so it fits over filler neck and then trim sides /top and bottom to fit.

I have been doing this for the last five years or so and it works well protecting the neck seal.
Do keep an eye on the drain tube as this is rubber , flush it with water to keep it clean when you wash the car and peel trim back and check it had not started to leak where it joins trunk floor.

allenying · #8 10-15-2016, 03:07 PM

hi, i've been using a rag tied around the fill tube, i think it works great, but now there's a bit of rust color on the bottom of the rag, could this be rust from the pipe itself?

i can change the rage to a fresh, since there was a specific spill incident with the biodiesel pump.

wouldn't a motorcycle inner tube also be made of rubber though?

Phillytwotank · #9 10-15-2016, 03:31 PM

Here's an idea... Don't spill any fuel on your stuff. It's not that hard.

allenying · #10 10-15-2016, 03:40 PM

yeah, and don't get in any car accidents either...
pumps aren't exactly drip proof, the pump at my biodiesel spot has been replaced, but i'm not counting on never getting drips anymore. accidents happen.

allenying · #11 10-17-2016, 04:07 PM

i imagine the rubber fuel filler neck grommet is supposed prevent fuel from dripping down the outside of the pipe, but is it also supposed to prevent fuel neck from banging around?

the rag i put in (picture from when i first put it in is attached) after a few months ended up with a a bunch of rusty stains, i took it out and cleaned the pipe down. i was thinking i'll put a fresh rag and try to be more careful of drips... there was 1 particular spill that i should've changed it right after... and/or try to cut out a piece of take out container plastic to go around the it, to prevent the drips from going down the outside of the pipe.

any thoughts?
thanks,

allenying · #12 10-17-2016, 04:39 PM

this was surprisingly easy to cut out of a circle salad bowl lid, i guess i can put the rubber grommet behind it, that'd prob be better than putting another rag behind it that will hold onto moisture

Squiggle Dog · #13 10-15-2019, 02:23 PM

I have this same problem, and it drives me crazy.

Quote:

Originally Posted by mach4

If I suddenly found myself in a situation where biodiesel was the only available fuel (and living in CA, that's unfortunately not beyond the realm of possibility)

What's wrong with renewable, clean-burning fuel, other than it attacking some natural rubber products? Making a new part out of Viton using the method you suggest is a good idea, and is probably the route I will have to take.

Quote:

Originally Posted by tjts1

WOW I'm glad we have renewable diesel instead of biodiesel in California. That can't be normal even for biodiesel. Imagine what it's doing to the inside of your fuel lines.

It is normal for biodiesel. And it might melt the inside of your fuel hoses, too, though I ran my original fuel hoses with no effect until I replaced them with a lined biodiesel-compatible hose. Once you have fresh biodiesel-compatible material in the system, the only downside is that it can gel at around 17 degrees Fahrenheit. But, it has a higher cetane rating than diesel, the fuel system will stay cleaner, and it lubricates the injection pump and injectors better than diesel.

Quote:

Originally Posted by Phillytwotank

Here's an idea... Don't spill any fuel on your stuff. It's not that hard.

I don't have a choice. At the only station that sells biodiesel here, they won't allow you to fill your own vehicle. They spill the fuel a lot and I have a bent fuel filler that I suspect they caused.

Quote:

Originally Posted by allenying

i imagine the rubber fuel filler neck grommet is supposed prevent fuel from dripping down the outside of the pipe, but is it also supposed to prevent fuel neck from banging around?

Yes, it keeps water and spilled fuel out of the trunk and also prevents the filler from banging around. Using a rag is better than nothing, but it will get saturated with water when it rains and will cause rust.

Also, these rubber grommets are no longer available. It might be a good time for someone to start reproducing them in Viton, as they would be the only manufacturer of this part, and they could sell them to biodiesel users who have been waiting for ages. They also apparently fit the R/W107, W116, W123, and W126 if I'm not mistaken.

allenying · #14 10-15-2019, 03:17 PM

thanks, unfortunately biodiesel is no longer available in NYC. I still have the plastic cut out around this grommet though. i used a rag before that but it would never dry and started getting nasty and maybe corroding the metal

Squiggle Dog · #15 10-15-2019, 03:23 PM

Quote:

Originally Posted by allenying

thanks, unfortunately biodiesel is no longer available in NYC. I still have the plastic cut out around this grommet though. i used a rag before that but it would never dry and started getting nasty and maybe corroding the metal

:/ I've noticed a lot of biodiesel stations closed around here in the past few years. Sadly, enough people haven't been supporting it.