My bio diesel fuel has a brownish gunk in it and it is plugging my primary filter. It is not bacteria problem (black specs in filter) I have been using Biocide.
Anyone have any ideas what could be causing this problem and what to do about it?
I haven't changed how I produce my bio diesel and this is the first time I have had this problem. I drive a few miles and the filter becomes cloged with this mes.
Any help will be appreciated.

A few questions since I don't know what your process is...

Are you dry washing or water washing?

Do you do any actual measurable soap tests or just a "shake em up" with water to guess if it's free of soap?

What did the oil titrate at when you started your batch, and how much glycerin did you end up with? Also, how large was your batch and how much methanol did you use?

You don't have to change your process for the oil to change, or the conditions for that matter either

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'98 E300 Turbo "Juliette"
'85 Federal 300TD

Biodiesel does clean the crap out of the tank and lines.It maybe rust also.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

Thanks for the feed back on my problem. For the record this is the first year in my 6 years of making Bio that i have had the problem. I water wash, don't know how to do a soap test other than to shake and look for the fine line between water and fuel.
I make 200 liters at a time and do a two stage process (18 liters methanol/675 grams of lye), heat oil to 130 degrees, mix in catalyst and mix with a pump for 1 1/2 hours.
Take a small sample and let oil and sample set over night. Next day drain glycerin and do 3/27 test of sample to see how much oil drops out. Usually 1 1/2 ml of oil drops, that means oil is 1/2 processed. If more I have to adjust amount of catalyst for 2nd stage.
I don't know how much glycerin drained off as it is thin and mixed with a small amount of fuel and won't harden for a while. It ends up about 8-10 gallons I guess.
I don't do titration. That is too high school textbook for a "backswoods" fuel making. Never found a PH meter that worked and PH strips? Forget them!
I do use a little clear vinegar after each rain water wash to make water drop out. Works great! Don't know what PH of fuel ends up being. Probably 7 or 8. After air drying fuel is a beautiful amber color and clear. My cars love it!
I did have a bacteria problem at same time (black specks in filter) but Biocide cleared that up. I have drained the fuel tank twice and gravity fed fuel through a primary filter and nothing showed up in the filter. With fresh fuel in the tank problem reoccurs. Must be warmth and agitation causing this mothery growth, but how to stop it?
Sorry for the winded reply but hti is basically all I know about Bio Diesel making and the problem I am having.
Thanks for helping.

Got any pictures of the "gunk" ?

Curious as to what it is... What kind of filters are you running the fuel through prior to putting it in the car?

Sounds like you got a process down that works, but if the oil changed you may not realize without doing a titration on it. The 3/27 is only a "guess", you can't really rely on it for conversion % unfortunately. Recently this has come up and it's turned out to not be as accurate as people thought. Having 1.5ml drop out doesn't mean 50% conversion.

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'98 E300 Turbo "Juliette"
'85 Federal 300TD