Oil/Water Pump

[roy]

On a 85 K100 what is the recommended procedure when replacing the oil/water pump shaft. I have read through the tech articles and they do a great job on seal replacement but do not mention shaft replacement policy.

1) Should both oil pump shafts be replaced as a set? or

2) Can just the one shaft be replaced?

BMW lists every part as a seperate entity so it is difficult to use that as a basis of what items should be replaced.

My only concern is that on most american made cars the oil pump gears are always replaced as a set.

[SweetT]

why are you replacing the shaft? Is it incredibly corroded? Granted I've heard the '85 K are different from later Ks but on my 91 I replaced the seals and reused the same shaft and gears and have had no problems...yet. :D

[deilenberger]

Roy temps me with numbered paragraphed questions:

On a 85 K100 what is the recommended procedure when replacing the oil/water pump shaft. I have read through the tech articles and they do a great job on seal replacement but do not mention shaft replacement policy.

1) Should both oil pump shafts be replaced as a set? or

2) Can just the one shaft be replaced?

BMW lists every part as a seperate entity so it is difficult to use that as a basis of what items should be replaced.

My only concern is that on most american made cars the oil pump gears are always replaced as a set.

The answer is #2.. but there is a caviat here. The '85 pump was different than later model pumps. The water pump impeller was held to the shaft by a nut that threaded onto a treaded end on the shaft. The threaded end of the shaft was prone to breaking off, destroying the front cover of the water pump when it did.

I believe (would have to check the part books) that the new shaft also requires a new water pump impeller. By the time you price these parts and the new seals you'll need (and the newest ones are not trivial to replace), in my opinion - you'd be better off buying the complete pump. I don't think the difference in $$ is worth the risk and work involved.

That's just my opinion.. so do as you may, but check if the impeller uses the same PN from '85 to '86..

Best,

[roy]

Roy temps me with numbered paragraphed questions:



The answer is #2.. but there is a caviat here. The '85 pump was different than later model pumps. The water pump impeller was held to the shaft by a nut that threaded onto a treaded end on the shaft. The threaded end of the shaft was prone to breaking off, destroying the front cover of the water pump when it did.

I believe (would have to check the part books) that the new shaft also requires a new water pump impeller. By the time you price these parts and the new seals you'll need (and the newest ones are not trivial to replace), in my opinion - you'd be better off buying the complete pump. I don't think the difference in $$ is worth the risk and work involved.

That's just my opinion.. so do as you may, but check if the impeller uses the same PN from '85 to '86..

Best,

Don, thanks for the info.

And yes you correct the 85 in in class by itself. Don't know if that is good in this case.

Where do you buy a complete pump? My local dealer shows everything broke down in pieces. I.e. the impeller, the impeller bolt, each seal, each O-ring etc.

My first thought was you buy a new pump just like every car I ever owned.

[jdiaz]

Roy, just give Chicago BMW a call and tell them you need the whole pump, plus a new "red" o-ring to go between the pump and the engine block. Then get a tube of RTV from the auto parts store (I think I've used Permatex high-temp in blue and red) and you are set to start the job. There is a procedure written up at ibmwr.org showing replacement.