85 K100 - Oil leak at rear of oil/water pump; does it need a rebuild or not?!

[paegelow]

Hey guys, long time lurker first time poster here.  I have an '85 K100RT with about 30k miles on it, and it recently started leaking oil where the back of the oil pump meets the engine.

I've read that if leaks coming out of that "weep hole" where the oil pressure switch wire goes through are a telltale sign that the oil and/or water pump shaft seal is going bad, but in my case it looks like the leak is actually at the rear mating surface.  I don't think anything is actually leaking out of the weep hole.

Also, I don't have any indications of coolant in my oil or oil in my coolant!

So my question is, what are the odds I can just remove the pump and re-seal the mating surfaces without doing a full rebuild?

Correct me if I'm wrong, but I've read that the pump rebuild can be tricky, plus the water seal design has changed since '85 so I'd have to replace the whole shaft anyway, which is expensive.  So I'd like to avoid doing the full rebuild unless I actually really need to!

[F14CRAZY]

It's worth a shot.

From my experience in trying to replace the water pump seal, it seems that your shaft must be smooth...pits are a no go. The pits form in the air space between the oil pump and the water pump. So you either have to replace the shaft (not cheap from the dealer) or attempt to fill it in with like JB weld and sand it. I suppose if you could weld it and turn it down with a lathe that'd also work.

[paegelow]

I went back and sat there and stared at the leaky area for like 10 minutes while the bike idled, and I think a tiny bit of oil actually is coming out of that hole where the pressure switch wire goes through.  A lot more comes through the mating interface though!  I think I might try just taking the pump off and resealing it and see how much of a difference that makes before I spend all the money on the rebuild parts...

[stokester]

Correct me if I'm wrong, but I've read that the pump rebuild can be tricky, plus the water seal design has changed since '85 so I'd have to replace the whole shaft anyway, which is expensive.  So I'd like to avoid doing the full rebuild unless I actually really need to!

I did the rebuild on my '93 K75 and don't know if your '88 K100 is the same but the new water seal is not what would require you to replace the shaft.  The new seal is of a ceramic design requiring a different size spacer bushing for me.  Check out the procedure and updates on http://www.ibmwr.org under Technical Articles, K-Bikes.  I made an update regarding the spacer which has never been posted.

[F14CRAZY]

Correct me if I'm wrong, but I've read that the pump rebuild can be tricky, plus the water seal design has changed since '85 so I'd have to replace the whole shaft anyway, which is expensive.  So I'd like to avoid doing the full rebuild unless I actually really need to!

I did the rebuild on my '93 K75 and don't know if your '88 K100 is the same but the new water seal is not what would require you to replace the shaft.  The new seal is of a ceramic design requiring a different size spacer bushing for me.  Check out the procedure and updates on http://www.ibmwr.org under Technical Articles, K-Bikes.  I made an update regarding the spacer which has never been posted.

You still may have to replace the shaft due to corrosion (if you don't opt to try fixing it)

[paegelow]

Oh yeah I guess you guys are right, it's not the updated seal design so much as I think I have the impeller that's held on by a nut rather than a bolt and from what I've read it'll almost definitely fall apart when I try to put it back together!

[rbm]

So my question is, what are the odds I can just remove the pump and re-seal the mating surfaces without doing a full rebuild?

It is very possible.  Make sure to clean both surfaces of the interface (pump and block) very very well; remove every and all traces of the previous sealant.  You'll be using an anaerobic sealant like Permatex Anaerobic Gasket Maker.  the recommended sealant, Drei-Bond 1207 is no longer available and a flexible sealant like Permatex Red is not strong enough to withstand the oil pressure in this application.  Apply the sealant sparingly and make absolutely sure not to allow any sealant to plug the high pressure oil return path on the block (circled in red):



In fact, it may be that this hole is plugged now causing your problem.  With the pump off the block, poke a thin copper wire into the hole to make sure it is open and not blocked.  When you do apply the sealant, follow BMW's recommendation for setting down the bead, fit the bolts and tighten them only finger tight until a thin bead of liquid emerges, then let set for 1-2 hours and finally torque to manufacturer's spec.  This procedure will ensure the best functioning seal.

[paegelow]

I'll give it a try!  Do I need to replace that large red coolant o-ring if I just remove and replace the whole pump?  I was thinking about taking it off today but I figured I should order at least that part first.

Is there a picture anywhere that shows exactly where and how much sealant to apply?  I have the Clymer manual but it doesn't really show anything.  I think I can figure it out but I'm just curious.

Thanks for the help!

[Howard64180]

Just as a side note, you seem to have confused the weep hole with the hole where the oil pressure wire goes through.  Here is a video of the actual weep hole weeping (turn your sound down):

[bizzaro]

I had pretty much the same issue with my 94 k1100lt.  It would leave an embarrassing puddle every place I parked.  Someone(idiot) had replaced the old pump with the new style and did not use any sealer on the mating surfaces!  The oil would seep down the wire chase between the cover and the housing or main block. Very hard to see exactly where the oil was coming from. 

Yes get the o ring.  There is also a smaller one on the shaft that I was told is not really a seal, but helps support the shaft. Both very cheap. Do it while ya got it apart. may as well. then do it  just as Robert said.

Clean the Cover, the housing and the engine block surfaces shiny clean. wipe dry with evaporating cleaner.
Get Ultra Black RTV. My local BMW shop mechanic recommended this  to bear up under the pressure, oil, and vibration.................so far so good for me(three months)
I used a tiny hole in the RTV cap to lay out a very small ridge all around the center of the mating surface on the engine block with a little help from tooth pick to help level and dab where needed.  Go extra light and clear around weep hole as circled in Roberts Pix. Don't want to plug that, but you do need a seal there.  Put your o ring in,(or both if you got um, its open so may as well, I would and did both. one is very small and just fits around the shaft).
put it all back together so the RTV is just squeezed enough to be touching both surfaces solidly. (finger or a just a bit more). Wait the recommended time to let the sealer start to cure and torque the bolts/screws. DO NOT OVER TORQUE! These are small bolts in alumimum and will strip very easily. I think it is 7 nm, but don't quote me look it up.   Also because some of the bolts/screws are behind the cover...........you may have to do it in two stages if I remember correctly and do the cover after the housing starts to cure? Let it dry for 24 hrs I believe it is. Good to go.  Mine has not showed any hint of oil since I did this............DRY AS A BONE. :riding: Lots of good vids on utube on replacing the old pumb with the new parts. Just watch them to get familiar with the tear down which is really pretty easy. 
As always.....................I could be totally wrong....................Good luck! (really pretty simple if you don't need to replace the pump)

[rbm]

I'll give it a try!  Do I need to replace that large red coolant o-ring if I just remove and replace the whole pump?  I was thinking about taking it off today but I figured I should order at least that part first.

If you're not sure of the age of that O-ring, then replace it.  It is a harsh environment and you'd hate to be doing this operation a second time because of a leaking $0.50 O-ring.

Is there a picture anywhere that shows exactly where and how much sealant to apply?  I have the Clymer manual but it doesn't really show anything.  I think I can figure it out but I'm just curious.

Thanks for the help!

There is such a picture but do you think I could locate it?  No.  I've searched through my stash of electronic information and can't find it; I know I used it when I did my engine rebuild.  It must be in paper form which I can't get to at the moment.

The bead should be about 1-2mm (1/16") round and be placed on the center of the mating surface, making sure to go completely around all bolt holes and not just the outside.  Steer as far away from the oil relief hole but still keep to the mating surface; you'll understand when you see it.

[paegelow]

Just as a side note, you seem to have confused the weep hole with the hole where the oil pressure wire goes through.  Here is a video of the actual weep hole weeping (turn your sound down):

Uhhhh oh you are exactly right!  Yeah I thought that big hole was what people referred to as the weep hole.  Alright so to be clear there's nothing leaking out of the actual weep hole on my bike!

Guys thanks for all the help!  I'm going to get those two o-rings on order and get this fix going asap!!!

[bizzaro]

OH, before I forget. there are about three or four different length screws in there. Mark um as you see fit! :yes

[paegelow]

Good call!!!

I have the two o-rings plus a bunch of other random crap on order, so as soon as that shows up I intend to knock this out.  I'll report back with results!!

[paegelow]

Alright I don't have my new o-rings yet but I decided to get a head start and get everything taken apart and ready to go when the parts show up.

I'm working on cleaning up the pump because the outside of it is filthy!!!  Anyone have any good ideas for flushing it out?  I want to make sure I have all the grit and crap out before I put it back together.  I think I might just wash it in the kitchen sink!

Also, I checked that U-shaped oil passage with a piece of wire and it actually seems to be clear.  I could put about 3" of wire in before it bottomed out on something.  I did find bits of black sealant all over the place everywhere else though.

[F14CRAZY]

A can of brake cleaner makes cleaning stuff like that super easy

[paegelow]

That's what I've been using so far.  I'm like a can and a half into it and it's coming along!  Still pretty dirty though.  I'm a little concerned because I can feel some grit if I turn the impeller, so I want to make sure I flush all that crap out before I put it back on!

[F14CRAZY]

I'll use a toothbrush for caked on stuff but yeah, brake clean is my go-to degreaser. I know what you mean with dirt inside...just keep flushing

[paegelow]

Alright after a few cans of brake cleaner I got everything cleaned up, and then I cleaned up the mating surfaces with 500 and then 1000 grit sandpaper.  My o-rings showed up so I got it back together today.  I used the Permatex Ultra Black RTV.  I put a small bead around everything on the back of the pump, installed it finger tight, and then torqued all the bolts down after letting it sit for an hour.  Then I repeated the process on the water pump cover.

Hopefully I didn't over do it with the RTV!!!

I'm gonna let it sit for at least a day before I fill the fluids back up, while I work on some other stuff!

[F14CRAZY]

You blasted it brake cleaner again after sandpapering right? I'm wary of sandpaper on mating surfaces...I stick with just a scraper but what I do and what you do are not necessarily wrong.

Sounds like you have time to wait but I stick with using The Right Stuff...zero wait time, which is good because my K is my daily rider

[paegelow]

Oh I blasted the living shit out of it!!!  Yeah normally I agree about sandpaper but this time it seemed like the best way to get everything off without scratching the surfaces or anything.  By the time I was done with the 1000 grit they were smoother than glass so if it leaks this time it'll probably be because I dorked up applying the RTV somehow...  I'm excited to see if this worked or not cause I don't really feel like doing it again  :riding:

[beemrdon]

Great posting. Please do a follow - up report on the success of the result.

 :clap:

[paegelow]

Great posting. Please do a follow - up report on the success of the result.

 :clap:

Will do!  Maybe tonight...  I just pulled the gas tank off to refill the coolant (what a pain!!!!!) and now I've found a bunch of other little lines and things to replace so I have to run to the store again.  I also have a bunch of other stuff taken apart including the gauge cluster, so hopefully I can get it all back together tonight.................. maybe  :dunno2:

[paegelow]

I think it actually worked!  I finally got enough stuff back together to start the bike today, and it let it idle til it was fully warmed up, and no leaks so far!

I still have a few things to do before I take it for a ride, so I'll see if it holds up.  But it looks promising so far!

 :riding: