I hooked it up to the battery and it makes noise, but does that mean that its actually working? I'm about to install a second WVO tank so I want to make sure my plumbing is working correctly.
Is there another way I can tell for sure if its working properly?

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1983 300D TurboDiesel

connect the battery and put it in water and see if it pumps.

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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

I guess I'm going to have to take it out for that. If air gets into the plumbing, how does it get out? I'm sure I'll lose a little coolant getting the aux water pump off and back on, so how do I purge the air?

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1983 300D TurboDiesel

Clamp both hoses before removing the pump; you will lose very little coolant and the air will come out if you turn the heat on and idle the engine awhile. Nose-up helps. OTOH, if the pump makes noise, it probably works. If you do remove the pump, add a fuse while you're at it. The W123 ACC-III system has no built-in protection from a frozen aux pump, which draws a high current and burns up the pc board traces in the PBU. About 1 or 1.5 amps for the fuse should do it.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970