Quite a while back I was boasting on line about making a hillbilly centrifuge pump for my bio processor. It worked beautifully --- for a short while. To refresh memories, I used a clothes dryer motor (120 v 1/3 hp) to drive a Chrysler power steering pump to drive a store bought centrifuge. Worked like a charm for maybe 10 hours and then started leaking pretty badly. Having many irons in the fire, I simply swapped out the motor and pump to the trusty Harbor Freight electric pump and settled for the 30 psi that it produced (as compared to the 80+ psi that my home made rig had been providing). Last week I finally got around to doing an autopsy on the power steering pump. Seems that the 2 O-rings in the pump were stretched way too big (hence the leak). I recall having read a while back that bio might cause certain materials to lose their elasticity. The O-rings were not soft or eaten up --- simply about 20% too big to do the job they were designed to do. Haven't had any luck finding the proper size bio resistant O-rings locally. At any rate, the Harbor Freight pump does an adequate job and the power steering pump was a freebie. I would ultimately like to upgrade to a more powerful pump, but I have doubts that pumps design to move power steering fluid are going to be the ticket for bio. Just thought I'd share these findings.

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John Schroader
bio burnin' 83 300D, '83 300 SD, '79 240D
"I've never met a man who was good at making excuses who was good at anything else" Ben Franklin
"You cannot permanently help a man by doing for him what he could and should do for himself" Abraham Lincoln

Power steering pumps are fine for this application, dare I say you chose incorrectly.
There are many more pumps on the market (ie: chrysler wasnt the only autp with p/s).

Check out the work of 'sunwzard' at http://biodiesel.infopop.cc

He used a p/s pump with great success.

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83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.