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Looking into biodiesel - '91 Jetta

Posted: Sun May 15, 2016 9:12 pm
by Sunny
I have a 1991 Jetta 1.6L, non-turbo.

I just got the car and I've been interested in this biodiesel I keep reading about (stuff that is sold at actual stations). The fact that it appears to be renewable really makes me quite happy about it.

Although, this vehicle is old.. and I assume everything in it is old.

I figured I'd grab a gasket/seal set when I got around to the timing belt this year and give biodiesel a shot after giving everything a good look over and replacing things as needed (as well as fuel lines?). But I keep reading that it's notoriously difficult to switch back to "normal" diesel due to rubber seals and gaskets swelling or even degrading.

Despite this vehicle's age, are there any gasket makers/sets out there that are actually rated to be fairly impervious to the effects of biodiesel for my year of Jetta? Or does this really just come with the territory and I gotta expect to replace the engine gaskets if I do run biodiesel on a regular basis?


Re: Looking into biodiesel - '91 Jetta

Posted: Mon May 16, 2016 2:14 pm
by Fatmobile
Bosch has making seals that work with biodiesel for years.
Do you know your car has a water separator (and check valve) underneath the car that is often troublesome. Causes fuel line restrictions etc.
Remove it and replace with pieces of 5/16" metal tubing.
Even if you don't use biodiesel.

Biodiesel can often clean out a tank. Clogging the intank screen, water separator and check valve.

Re: Looking into biodiesel - '91 Jetta

Posted: Mon May 08, 2017 4:31 am
by ef5ef

Re: Looking into biodiesel - '91 Jetta

Posted: Tue May 09, 2017 9:52 pm
by greg lousy
the standard material for replacing rubber parts for biodiesel is called "viton"... I P seal is a bit touchy and your right, timing belt change would be the perfect time. Other than that I think its just the rubber hose lines, again viton and readily available - 3/8 ". I got a seal and researched it a bit but ended up running WVO, which is friendly to old standard rubber parts

Re: Looking into biodiesel - '91 Jetta

Posted: Fri Oct 05, 2018 7:42 pm
by ad
I have been running been running biodiesel in my '91 for years.
Started on WVO 14 years ago, did that for a few years, then regular diesel for a few years, and now biodiesel for the past 5 years.
Right now I have over 319,000 miles on the car.

I have made my own BD and I now buy 100% BD from a local brewer. I usually run about 50% mix.
Never had any biodiesel related seal problems.
Never had any clogged filters.
Never had any water separator issues.
Injector pump has never been opened and doesn't leak.
The only problem is the little fuel return lines on the injectors start to seep and get replaced every couple of years. Apparently everyone has this problem, running BD or not.

If you are buying biodiesel at the pump, it is likely a blend of only 5%-15% biodiesel. This will not harm any rubber, or will only do so very, very slowly.
It only becomes a problem if you are running 100% BD continuously so the rubber is always immersed in BD.

If You are frequently running >75%, here's what I would do:
Fuel lines are the only thing I would consider replacing.
Keep a spare fuel filter in the car and tools to change it (screwdriver), as the BD may loosen up some junk.
Keep a roll of injector return line in the car.

Again, if it is only ~5% from the pump, dont do anything.