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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: orforester on December 03, 2013, 10:07:16 PM
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So I am rebuilding a FY RS into an RT, and in the process was rebuilding the water/oil pump. Did this on my 89 RS a couple of years ago, piece of cake, but this one is different. The shaft has a stud instead of a using a bolt to hold the impeller on. I used the proper torque and snapped the stub off, OH CRAP. Noticed several on FleaBay that look exactly the same. Was this a design flaw? Has anyone else run into this problem?
I got a new(used) one coming so I got it covered, but still....
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Sounds to me like you have the old style pump. The old style used a cast impeller with a retaining nut as opposed to stamped steel and a bolt.
You will more than likely need to update it to the new style which is basically(IIRC) everything inside the housing...... impeller, shaft, seals. Someone that has done the actual conversion will know better than I. According to the fiche's It looks like the old style was used up until 1/90.
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Hi,
I have just done the oil/water pump job myself I found that I had the old cast impeller and upon changing the seal kit I purchased the new type impeller "much better" and all parts easily available.
BIG D
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Found a guy in Oregon City (close) on FleaBay who sold me a whole water pump (shot) so I am going to use that impeller, it is the new style. Have or ordered a new pressed steel fan/wheel. Should be coming along fine. Just wondered if anyone else had the "broken shaft" problem. Seems like it would hold up just as well as the bolt style, but I guess not as I broke mine.
I wonder how much it would be to have it drilled out and tapped for a bolt............if I only had a metal lathe...........
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BMW did change from nut to bolt somewhere late -85, just because it was a lot of shafts that did end up as yours.
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You'd think BMW would have learned a lesson about the small diameter shaft with a threaded stud instead of a tapped hole after the great airhead cam nose debacle. A whole lot of those poor things have been reefed on and snapped clean off.
For what it's worth, I just did this job and learned a lesson. Although my pump has the later style shaft with a tapped hole, the procedure is the same either way. I used the new seal which is common to all brick K bikes and I found it very easy to install flush using a large socket. Installing the shaft was also easy by drawing it through the seal with bolt and washer. But I somehow missed the fact that the old style cast impeller is not suitable for use with the new seal. Installing it will compress and ruin the seal and you have to start all over. The impeller is not the correct depth for the new style seal, and after you tighten the bolt/nut, you will find that the shaft is now locked up tight.
So, make sure you have the newer style stamped steel impeller and its required spacer to use with the current water seal.
Don't forget the oil seal behind the water seal, and the small o-ring for the drive gear shaft end, the bigger red o-ring for the coolant passage, and I thought it was worthwhile to renew the crush washers on the relief valve and temp/pressure senders or plugs while I was in there. No more leaks!
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Also - if you have already installed the shaft you now need to replace, you should replace the seal. There is no way to tap the shaft back out without wrecking the seal. You probably knew that already - but just in case. :)
I also had a new oil seal on hand when I re-did my water seal. It's difficult to get the water seal out without wondering if you've nicked the oil seal.
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Old style pump. Rebuild parts are few and far between.