Mine was corroded pretty bad inside....fixing it was more than any mortal could have done. Mine was actualy a worst case scenario.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

I saw on the manual that a rebuild kit is available for these pumps , it even listed a part number for the kit. Of course I didn't need it then (or now) and now I can't find it on the CD.

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Democracy dies in darkness, you have to kick at the darkness till it bleeds daylight

I was fiddling with mine last night on the bench......I took it nearly completely apart....The $135 dollar question (will it work on reassembly) will be asked and answered in a few days....There are lots of itty bitty little parts in a certain sequence....The interior of the motor case had some corrosion but not much.....

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Rob M
Norwich, VT USA
1980 240D Euro delivery 4 speed manual silver/blue
~160K miles

mine has been working fine since early January when I took it apart. The brushes were worn and had a little crustiness on the surface which I scraped off along with sanding down the commutator surface and combing the copper dust out of the grooves with a nylon pick.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

Great info on this forum!

Instead of paying $130+ to buy a new pump, I gave the rebuild a shot. I've got a 603 (87 300D) and, after removing from the car, the end with the electrical connector was very easy to remove (just carefully bend out 4 tabs only as far as necessary so as not to break them). Then, work the black plastic end out and you're left with the brushes, springs, etc. in a nice little assembly. Make sure that the motor/impeller spins at this point (you don't need to take it out, though - just clean out with compresed air).

I purchased (in the US) a Borg Warner X363 alternator brush set (or CarQuest FX-65 or equivalent) which were about 2x as wide as needed and slightly too long but otherwise perfect. One box has 2 brushes. The wire comes out of the side which is a requirement of the spring mechanism. After purchasing:

1. Grind down (by hand on a metal file or use a bench grinder w/ fine wheel - it goes fast) to 3/8" long. Hold it carefully - too hard and you'll break them which is why the file method is probably preferred. Of course, I didn't do it this way
2. It's roughly 2x too wide - grind down the side opposite that the wire comes out of to match the width of the existing brushes.
3. Using a small triangular file (maybe 1/4" or so on a side) make a grove in the end to match the existing brushes -- this is where the spring sits.
4. Take note of how the wires are routed (or just do one side at a time)
5. Push spring aside (my motor had a little notch to hold it above the brush), pull out the brush, and pull out the crimp connectors for each brush - carefully open up with a crimping tool or needle-nose pliers and remove the old brush and wire
5. I soldered (don't want to get in there again) the new wire from the brush to the coil and then recrimped the connector back on.
6. Insert the brushes (routing the wire properly)
7. Put the spring back and the crimp connector back into it's hole
8. Repeat for other side.

Now, the slightly tricky part. It worked perfect for me (the first time, not sure how that happened). After assembling, push the brushes back out just far enough that the spring comes off the back and over to one side. The brush should still be within the edges of the housing so that you can get it back onto the motor. Clean up the inside end of the motor and put a little moisture on the o-ring to help ease it back in (not sure if it's oil tolerant) so you'll have a seal. Then, carefully put the end back on motor housing being careful to line up the "key" on the end with the notch in the motor housing. Then give it a little bang on the brush end with the handle of a screwdriver to (hopefully) release the brushes enough for the spring to jump back in place. Test using leads before reinstalling - if it doesn't work, one or both brushes didn't release (or you have another problem). Bang again or take apart and try again. When it works, crimp ends back and reinstall.