If you are using commercially produced biodiesel there should be no methanol in it whatsoever. The mehtanol and other residuals of the reaction are either recovered or washed out. The only way you would find residual mehtanol is if you were using unwashed homebrew. The methanol will dry out rubber and cause it to crack more often than melting it.

Biodiesel will melt, over time, natural rubber, but then again so will oil, any oil, whether Veggie or Petro. Oil and rubber don't mix so well, which is why they always caution you about spilling oil on your rubber belts.

The other issue at hand is the fact that Marlene is a 20 year old car. All be it a Mercedes. It is time to replace those old hoses regardless. I have been running well washed and well made homebrew (it's my full time take all my profit job) for several years now in my '83 and the only problems I have had besides the usual tank degunking period (which by the way required 4 prefilter changes and 1 main filter change over the course of a year) were the braided fuel lines going to the expansion tank behind the spare wheel. After calling my friend down at the Mercedes shop I was informed that Mercedes still use rubber fuel lines, so I replaced these with standard fuel line available from the local parts store. No problems. Hell if these last 10 years instead of 20, no big deal. The only other hoses I have replaced were the litte pieces going to and from the prefilter as I was always getting BD all over the hoses every time I had to change it out.

The biggest mess so far from the years of B100 use is the breather tube around the filler neck. These melt and turn to goo (and I mean goo!) in every biodesel I have seen so it is worth ordering two (by the way I order the prefilters by the box and keep them and a 4in1 under the seat).

How did they determine it was rubber? I can still get black grit in my prefilter even after all this time when I am foolish and start to run out of fuel (I need to fix the fuel guage!) but more often when I am on the road and have to mix in Petro diesel and do the same thing.

What you can do is replace the lines now with stock tubing and order the viton to have on hand when and if these deteriorate.

__________________
Jeff
AKA: "El Jefe de Biosmell", at your service.
Locally brewed B100 100% of the time.

83 300TBD-T 300,000+/3+years B100
82 Datsun 720 Longbed 86,000/B100
81 300D AKA: The Turd/parts(gone to the bone yard)
75 O309D AKA:The Blue Turtle/76,000

83 VW Golf Diesel/ Girlfriend's
83 F250/ Girlfriend's
Sold all the gas burners!