K75 oil pump popped seal after renewal; due to blocked high press return hole?

[Ted]

Dear all,

Due to my 1992 K75RT marking it's spot with oil while parking I decided to pull the oil/waterpump and replace it's seals. All went without issues but after installation and some testrunning I had a much larger oil leak than before. So removed the pump and redid the installation of the pump using fresh Dreibond 1209, paying close attention to getting the sealant evenly spread without clogging up the high pressure oil return path hole as described here. Cause I did find I had accidentally clogged the hole the first time :-(

So after reinstallation I filled oil once more but now I had a running leak without even starting the engine. After removal of the pump and disassemby of the shaft I found the oil seal had become dislodged from it's bore and was loose inside the cavity. So either I did not install the seal right; or it doesn't fit snug enough, or it 's blown out by high oil pressure.

So there's my question: can a plugged high pressure oil return path cause an increased oil pressure? And what can I do to clean the hole? I ran some steel wire in it, it went about an inch deep. Can I blow compressed air into the hole? What's inside?

Thanks and greetings from the Netherlands.

[Laitch]

Did you use the type of parts and method discussed here?

[Ted]

Well I used the ibmwr.org writeups here and here but reviewed your link and I can't find any deviations from my procedure. Except for the use of dreibond1209 instead of some black sealant used in your link. I did use all seals shown, including the new style waterseal together with a new type bushing and a new turbine wheel.

Nice writeup you linked, very clear with all the pictures.

[Laitch]

Can I blow compressed air into the hole? What's inside?

Failure of the seal after a first experience with its  isn't uncommon. Is there corrosion on the impeller shaft? Regarding what's inside?, these drawings from the on-site BMW workshop manual might help.

[know_fear]

Ted, I have been fighting an oil leak at the pump for a while now as well.
I replaced the oil seal and water seal and thankfully those have been working well though there was a bit of a "break in" period when the water seal leaked a little bit out the weep hole. It took about 3000 kms to seal completely.
My oil leak is between the oil pump body and the engine sump, right at the top of the pump. I just disassembled it again to inspect the little hole that RBM has said could cause trouble if plugged. Mine was not plugged and on further examination I cannot see how it has anything to do with oil pressure relief. The high oil pressure relief system is a spring loaded piston within the oil pump itself. If the oil pressure is too high the piston is pushed towards the right side of the bike against the spring. This opens a passage which allows oil to flow from the high pressure side (on the left) to the low pressure side (right side if bike). Before installing the pump back on the engine you should ensure that this piston is free to move and is not jammed. I'm sure that relief system operates when a cold engine with thick 20W-50 is first started. If the piston is jammed the seal between pump and block will be compromised.


Good luck

[Ted]

Thank you Laitch and know_fear for the helpful replies!

@know_fear: that's a very sensible idea to inspect the pressure regulator a bit closer. Perhaps it got clogged with a bit of dirt after the removal of all the sealant rests. I did clean up really well but you never know.
Agree with you on the function of the little hole, it seems it's only function is to drain oil that has leaked into the ) shaped cavity of the pump back into the crankcase. I read a few times that if this hole is clogged that might lead to an external leak at the 2 o'clock position of the pumphousing. And indeed, that is right were the little drain hole is when viewing aft. So it is important to keep the hole open to prevent external leakage, but to me it seems improbable that a clogged hole caused the dislodged seal that I experienced.

@Laitch: yes this was my first time round with this job, and errors can be made so I will be extra careful on my next try. I plan on installing the oil seal with dreibond, that should help to keep the seal in place.
I have ordered a new shaft, the old one was in reasonable condition but I just want the bike running again (it's my daily driver).

Will keep you posted on the outcome :-)

[Ted]

Fixed it.   :riding:

After fitting the new oil seal, I test-installed the (new) pumpshaft. Getting the shaft in is not very easy because the shaft does not have a nice chamfered edge so I lubed everything with oil and installed the shaft by turning and gently pressing. The first time went well. Tried a 2nd time, and I immediately pushed the seal out again. Apparently the seal was not tight enough in the housing. The seal ring is 6 mm high, with round edges so you have only like a 5mm mating surface. Perhaps my pump housing is a bit large or the seal is a bit too small but anyway; if you push out the seal ring this easy, there's a fair chance this happens when installing the shaft for real. And you will not see or feel you pushed the seal out while assembling the shaft, you only know that it's wrong after you pour the oil in it.

So I changed the procedure a bit:
- Glued in the oil seal with a dreibond and let it dry overnight
- I made a bushing 4.5 mm high from a piece of aluminum pipe. It fills the gap between the oil seal and the coolant seal. The coolant seal is really tight, so the oil seal is well supported and can not get out. I provided a leak hole in the bushing. And installed it with dreibond to prevent it from rotating.
- Next I pushed the shaft through the oil seal and checked if it stayed in place.
- Finally I installed the coolant seal and pulled through the shaft the final part.

Drove some 150 km by now, not a single drop. Happy! :-)

Thanks for all the help!

[know_fear]

That's good to hear Ted.
It will be another month before it's warm enough to ride here.
I hope my leak is sealed and I can put the belly pan back on.