Rebuilding alternator and PS pump - 1987 S4
04-06-2015, 02:38 PM
#1
Addict
Rennlist Member
Rennlist Member
Thread Starter
Rebuilding alternator and PS pump - 1987 S4
Hi all,
I am (still) working on my brother's old car to hopefully get up for sale before summer. I should post a general update on that but of more general interest is likely the PS pump and alternator rebuild.
This car is a 1987 928S4 5-speed with a Murf Stage 2+. I am in it doing a timing belt and water pump, and hopefully addressing a noisy and foamy power steering system as well. I am installing new upper PS hoses and also installed a Rennbay PS rebuild/reseal kit which some people have reported as a fix for the noise and foamy fluid. I guess we'll see. This Rennbay kit I think is generally sold as a 944 kit but fits a large number of cars including the 928, some BMW, some Audis, etc. I'll update when it's back in service. Before I put it all the way back together I plan to flush the rack with new fluid via the upper lines. The kit is only $20 from Rennbay, a bit more from other retailers.
While I had the ancillaries off I decided to clean up and check out the dirty alternator, and I was glad I did as I found the brushes to be badly worn and the bearings a bit gritty. It's super easy to at least check the brushes and bearings and I recommend this during a belt job as part of your PM.
I ordered up bearings and brushes and will get those swapped before putting it all back together. Some people change the voltage regulator but I have found the old ones to be nice robust chunks of silicon and I distrust the cheapo new ones. This one I believe is the original one from 1987.
The bearings I believe are 6303-2RS and 6201-2RS, the brushes I chose are Standard FX-45 which are a Volvo 240 fitment but I think they are correct, will advise.
I have rebuilt alternators before with success. Changing the brushes is pretty easy and there are youtube vids you can consult. You basically drill into the graphite until it explodes, avoiding drilling so much you wreck the spring behind it (although some brush kits include the spring and so it's no big deal) then remove the spring, then drill through the wire and solder joint and remove the wire braid. It's easier than it sounds. (actually I wonder if you can't drill from the opposite side and drop out the brush and spring intact?) If the new brush comes with a stiff wire leader, that's helpful as you can poke that leader through the new hole, solder and cut off excess. If not you can tin a few mm of the braid so it can be poked through the hole, or solder on your own leader. A soldering gun or beefy iron is usually needed for this. Regulators (with new brushes fitted) are maybe only $30 but I am not sure if $30 gets you a good one or the cheapest chicken in the shop.
Slip rings have very thick copper bands on them and I feel they last though a couple of sets of brushes. These are not badly worn at all. Some people use a lathe or drill press to reface the slip rings during a rebuild. I am not sure this is needed as the old brushes were able to run well on the worn ring and the new ones will very quickly conform. I might face these, we'll see. The alternator is whining a bit in my other 928S4 so I bought extra parts. I think I have one or two spare alternators as well and I plan to make sure one of those is rebuilt and ready to go.
There is a good thread with pics on the 944 alternator rebuild, same alternator in the S4 and in the 85.5+ 944:
https://rennlist.com/forums/924-931-...r-rebuild.html
Questions and comments welcome. I'll update this thread when I have more details.
-Joel.
I am (still) working on my brother's old car to hopefully get up for sale before summer. I should post a general update on that but of more general interest is likely the PS pump and alternator rebuild.
This car is a 1987 928S4 5-speed with a Murf Stage 2+. I am in it doing a timing belt and water pump, and hopefully addressing a noisy and foamy power steering system as well. I am installing new upper PS hoses and also installed a Rennbay PS rebuild/reseal kit which some people have reported as a fix for the noise and foamy fluid. I guess we'll see. This Rennbay kit I think is generally sold as a 944 kit but fits a large number of cars including the 928, some BMW, some Audis, etc. I'll update when it's back in service. Before I put it all the way back together I plan to flush the rack with new fluid via the upper lines. The kit is only $20 from Rennbay, a bit more from other retailers.
While I had the ancillaries off I decided to clean up and check out the dirty alternator, and I was glad I did as I found the brushes to be badly worn and the bearings a bit gritty. It's super easy to at least check the brushes and bearings and I recommend this during a belt job as part of your PM.
I ordered up bearings and brushes and will get those swapped before putting it all back together. Some people change the voltage regulator but I have found the old ones to be nice robust chunks of silicon and I distrust the cheapo new ones. This one I believe is the original one from 1987.
The bearings I believe are 6303-2RS and 6201-2RS, the brushes I chose are Standard FX-45 which are a Volvo 240 fitment but I think they are correct, will advise.
I have rebuilt alternators before with success. Changing the brushes is pretty easy and there are youtube vids you can consult. You basically drill into the graphite until it explodes, avoiding drilling so much you wreck the spring behind it (although some brush kits include the spring and so it's no big deal) then remove the spring, then drill through the wire and solder joint and remove the wire braid. It's easier than it sounds. (actually I wonder if you can't drill from the opposite side and drop out the brush and spring intact?) If the new brush comes with a stiff wire leader, that's helpful as you can poke that leader through the new hole, solder and cut off excess. If not you can tin a few mm of the braid so it can be poked through the hole, or solder on your own leader. A soldering gun or beefy iron is usually needed for this. Regulators (with new brushes fitted) are maybe only $30 but I am not sure if $30 gets you a good one or the cheapest chicken in the shop.
Slip rings have very thick copper bands on them and I feel they last though a couple of sets of brushes. These are not badly worn at all. Some people use a lathe or drill press to reface the slip rings during a rebuild. I am not sure this is needed as the old brushes were able to run well on the worn ring and the new ones will very quickly conform. I might face these, we'll see. The alternator is whining a bit in my other 928S4 so I bought extra parts. I think I have one or two spare alternators as well and I plan to make sure one of those is rebuilt and ready to go.
There is a good thread with pics on the 944 alternator rebuild, same alternator in the S4 and in the 85.5+ 944:
https://rennlist.com/forums/924-931-...r-rebuild.html
Questions and comments welcome. I'll update this thread when I have more details.
-Joel.
04-15-2015, 02:25 PM
#2
Addict
Rennlist Member
Rennlist Member
Thread Starter
Update: I got the parts in and replaced the bearings and brushes. The FX-45 brushes work but are a bit shorter than stock, this is probably OK as the slip rings are also worn so having brushes that last 125K is not necessary.
I did reface the slip rings, I decided to try doing it on my drill press using the old rear bearing to support the other end. I'm not sure I recommend this, it could be pretty dangerous, you could end up with a mill file jammed in your chest. I was careful and my drill press can run as slowly as 500 RPM.
6303-2RS and 6201-2RS bearings were correct for the late 928 alternator. I bought "premium" HCH bearings which were maybe a buck more than the value brand. The premium bearings are $3-$4 depending on size and have a reassuringly hologram-emblazoned package with TUV and ISO 9001 certification marks.
I've only tested the alternator with a battery and a drill to spin it up, but it seems to work. I am looking to replace the alternator "hat" or cooling bonnet, if anyone has one please let me know.
I did reface the slip rings, I decided to try doing it on my drill press using the old rear bearing to support the other end. I'm not sure I recommend this, it could be pretty dangerous, you could end up with a mill file jammed in your chest. I was careful and my drill press can run as slowly as 500 RPM.
6303-2RS and 6201-2RS bearings were correct for the late 928 alternator. I bought "premium" HCH bearings which were maybe a buck more than the value brand. The premium bearings are $3-$4 depending on size and have a reassuringly hologram-emblazoned package with TUV and ISO 9001 certification marks.
I've only tested the alternator with a battery and a drill to spin it up, but it seems to work. I am looking to replace the alternator "hat" or cooling bonnet, if anyone has one please let me know.