From: Martin Jagersand
Symptom(s): Slow starter, No starter
date Aug 18, 2007 11:12 PM
subject Starter motor do-it-yourself rebuild
I just rebuilt the starter for my '82 Diesel Westy. Last time I did it was
in '99, I think, so the previous rebuild lasted about 8 years.
Bosch rebuilt starters can run near $200 nowdays, but rebuilding it yourself
is not hard. Here are some tips:
First check that the problem is really the starter. Measure the voltage over
the starter itself while cranking, ie from the positive iput terminal on the
starter to the starter housing. If it's 8-10V and the starter still is
cranking slowly the starter is most likely bad. If battery voltage is ok but
voltage at starter is low check voltage drop in the positive and negative
circuit. When I measured I had .2V drop in the neg circuit and .9V in the
positive. Of the .9V .7V was over the solenoid and .2V in ther actual cable.
ED. Note: See Bentley 27.13 for diagnostic flow
If it is not starting at all, no noise, no click, despite having 12V at both
starter and solenoid, check connections to the solenoid, and then between
solenoid and starter. This time I found that the metal tab running from the
outside of the soloid terminal and connecting the solenoid winding was
sheared off. I soldered on a flat piece of copper (from a water pipe ground
strap) to fix it.
So you determined that its the starter. All Bosch starters, gas or diesel
have the same basic design, but the sizes and housings are different between
different models. Get the right parts!
Wear parts are basically:
1/ Bushings: 3 total. One in each end, and one in the middle. The latter I
don't think carries much load. Cost: about $1 each from the Bosch
2/ Brushes: 4 in total. You can buy either a brush assembly for $45 with the
4 brushes already mounted, or 4 loose brushes for about $15 total. If you
get loose brushes get ones with small u-shaped metal ends welded to the
copper braid. They are much easier to solder to your brushholder.
The above is Bosch prices VW dealer prices are about twice as much.
1. Unscrew the two small screws on the commutator housing (back) this
releases the brush holder.
2. Unbolt the two studs in the back. Now the commutator end comes off after
removing a circlip on the end of the shaft, and the rotor is loose, but
don't pull it off yet.
3. Loosen the 3 screws holding the solenoid to the front housing.
4. Between the solenoid and the starter motor is a small rubber piece. See
if you can loosen it. Carefully wiggle and separate the front housing.
5. Solenoid and starter can be separated at the solenoid end. Take off the
solenoid. (To prevent binding wipe off any dirt or corrosion on the solenoid
plunger before reassembly)
6. Determine shape of bushings. The gear end bushing is in the bellhousing
on starters for transverse engine models, and in the front housing on
longitudinal engines. Replace front and rear bushings if worn.
7. To get at the middle bushing remove the ring and c-clip in front of the
gear. Slide off gear assembly. Take out plate holding middle bushing.
Replace if worn.
8. Check brushes. New brushes have about 8mm between the tip and the copper
braid. I'd replace them if they are more than half worn. Also if the
bushings were really bad the starter shaft has been riding out of center,
and the brushes have been wearing irregularly and need replacement.
9. Snip off the braided copper holding the old brushes. Don't lose the
springs! File off any remains from the brush holder. Solder on new brushes.
Make sure they are soldered well. Each brush will pass 100's of amps at
10. Inspect the commutator. If pitted (from arcing) file down until clean
copper. If out of round use a lathe.
11. Assemble the parts. Grease bushings and gears lightly. You don't want
grease on the commutator or too much so that it can spatter on the clutch.
University of Alberta
> I have a 2.1 starter that I (from time to time) try to get that
> c-clip off. It's very frustrating.
> Maybe the diesel starter is that different from the 2.1 starter?
> Maybe it's just me? At any rate I'd love to get that gear off my spare
> Thanks for the write up, it's a keeper.
Mine has a c-ring inside covered by another ring outside.
Tapped off the outer ring with a 1/2" deep socket,
and took off inner c-clip with pliers.
One more note for completeness:
If your starter motor runs strongly, but the starter gear quickly disengages from
the flywheel (hence not cranking motor more than a fraction of a turn), the
culprit is often that the starter bushings are worn unevenly, allowing the
starter motor shaft to wobble and the starter gear out of engagement with the
This symptom is particularly noticeable for Diesel owners here in the north,
since the starter torque needed to crank a Diesel in the cold is very high,
hence even a slight shaft misalignment will push the gear out.
I think it always pays to change at least front and rear bushings even if these
look ok. Middle bushing I think plays less of a role. (and even new ones are quite
loose. I suspect they are there more to center the middle plate on assembly
of the starter, than to have any function when the starter runs.)
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