Is Viton/Plastic Lined Hose Really Necessary When Using Biodiesel?
 

I have used B99 biodiesel in three different Mercedes for a period of about 7 years.

The first car was a 1979 W116 300SD. I bought the Parker hose that is sold as "biodiesel compatible" with the plastic lining in it, purchased from a popular Mercedes parts source. I found that it would get gooey in only a week or two and would start melting at the hose clamps. Pretty soon the hose would dissolve and leak, causing me to have to replace it. It seemed that the rubber part of the hose was not biodiesel-compatible, and that the plastic lining was all that was protecting it. When changing fuel filters, if any biodiesel got on the outer hose, it would melt it. I used Viton injector return lines, which worked, but were prone to splitting and didn't seal very well.

The next car was a 1968 W110 200D. I used the Parker lined hose again. Same issue, any biodiesel that got on the rubber part of the hose would cause it to become gooey.

Finally, I am driving a 1980 W116 300SD. It still has the old natural rubber hoses. The cigar hose is hardened and most of the hoses have the Mercedes logo on them. I started using B99 in it 4 years ago. I planned to replace all of the hoses, but kept putting it off, and after 4 years, I am still running B99 with every tank and still have all the old rubber hoses installed. But, here is what is interesting: none of the hoses are leaking! None of them have become gooey or melted, even after being soaked in biodiesel when changing filters. In fact, the factory rubber hoses are outperforming the "biodiesel-compatible" hoses. What gives?

I am starting to wonder if I should even use "biodiesel-compatible" hose.

Here's the rundown of biodiesel compatible materials.
http://www.biodiesel.org/docs/ffs-performace_usage/materials-compatibility.pdf?sfvrsn=4

I think most automotive fuel hose sold today is bio compatible.

Thanks. Interesting that it lists Tygon as not being compatible, yet it is something people are (possibly mistakenly) using in biodiesel conversions.

Gates Barricade brand hose is biodiesel resistant and is available at NAPA.

Again
 

You would not believe how good PEX works and how affordable it is.

Questions on PEX - how do you make it conform to multiple tight bends and how do you attach it? Barbed fittings? It seems awful hard to be slipping over barbs.

Another note - I was considering buying some of the biodiesel rated lined 3/8 and 5/16 hose and I was going to have to buy a whole 25' of it. Would anyone be interested in buying some of the extra hose I would have left over?

Something like this: Amazon.com: Goodyear 65153 SAE 30R9 Fuel...

PEX
 

PEX is actually rather flexible. I have run multiple 3.0L 5 cylinders with only PEX for fuel line and no hose clamps. The only place it can not be done is one fitting off of the lift pump it is smooth and it does not seal well. I use 1/4 inch for the fuel line I purchased 100 feet 5 years ago for $30 from a plumbing store. My 2006 CDI uses it with a 70 psi fuel pump.

The trick is to just add a little heat sometimes I use a Phillips head to widen it and then it slides on and shrink wraps itself to the fitting. I use Push-lock fittings. I use flare fittings and push locks so that it will last, and I can remove it. If you need to make a tight corner a little heat and then let it cool and it stays in that position. Remember if you make to tight a corner with rubber hose it will kink also.

I would not pay $150 for 50 feet of Goodyear hose. Try the Pex if you can not get it to work you wasted $10 and an hour of work but it is going to work well.

OK, that's a good idea. I want to replace all of the under hood hose and connectors with aluminum/brass fittings and some kind of tubing. I'll do some research on the PEX solution.

If the bend is too tight for PEX then use Gates Barricade low pressure fuel hose for tight bends and standard PEX brass fittings for transitions. Use a brass PEX coupler with a PEX crimp ring on one side and a hose clamp for the hose side. Mix PEX and Barricade as needed. All the parts are available from a hardware store and an auto parts store. Simple, easy, cost effective.

hi, i've been reading the various posts on various forums about running biodiesel in a mercedes diesel, this is the most recent post i could find, as most are a few years old, so i'm wondering if any of the info has changed.

are the regular rubber hoses fine for biodiesel?
even the ones that get heated?

what if you're only running B99 say... 1 week a month, out of 4 total fills per month?

i feel the original poster's Q wasn't really addressed.

thanks.

regular rubber hoses will melt / leak over time when being used with any high percentage biodiesel. rubber will work, for some amount of time...how long is unclear. six months to a year or so is my experience. heat will accelerate the degradation process.

rubber, buna-N, nitrile = not compatible

viton = compatible

viton is compatible and will last forever. i have yet to replace one of my viton lined hoses in 7 years. if you are investing the time in a car and want to run bio safely over time, run viton lined hoses. bottom line.

aha viton hoses last 7 years, that's amazing, that was actually another q i had, since nobody else in the forum posts from 2010-2013 i read really said anything about how long they last. i almost wondered if it would be easier to just use the regular rubber hoses and change them every year, but lasting 7 years is much better. it's strange that some people claim they have no issues with the rubber melting away.

thanks,

My 300SD still has the old rubber hoses with the Mercedes star on them. I've used B99 almost exclusively for almost 5 years. A few months ago the one at the tank started getting gooey.

In other vehicles, I have used the Parker hoses with the plastic inner lining. The lining does a great job of keeping the hoses in good condition. But if the biodiesel leaks out onto the rubber, it will make the rubber swell. If the rubber is in contact with the biodiesel for more than a few days, it will start to turn gooey. So if you get any biodiesel on the rubber part of the Parker hose, wash and rinse it off as soon as you can.

I installed a set of Parker hoses on my roommate's 350SDL. While I had the injection pump off, I plugged one of the hoses with a bolt. But the tank breather valve was clogged, so excess pressure in the tank forced biodiesel out the end that was plugged with the bolt. The hose swelled up at that end and I thought it was ruined. But I cleaned off the biodiesel and hooked it back up. Over time the swelling seemed to go down, and so far, so good.

I tried Viton on the injector return lines, but it was very brittle and can not be reused at it tends to split.

I think that the original Mercedes rubber hoses are better able to withstand biodiesel than the rubber part of the Parker hoses, but the plastic lining in the Parker hose keeps the biodiesel from contacting the hose, so the Parker hoses work better as long as you keep biodiesel off of the outer surface.

I plan to install Parker hoses on my 300SD as soon as I have the money (no job at the moment and just had to move into a new place).

well, i wonder if the gates barricade hoses are natural rubber on the outside.
i suppose it's still safer to go with viton, parker, or barricade, and which of the 3 is less likely to make a difference.


is it still the consensus to not change the smaller injector return lines because they come off more easily?

1 or 2 people said they did change them and it was fine, but more reported not to, and again these convos were all 7 years old.

thanks!