Bosch Gen4 Seal Service & Grease up

[RustyMTB]

I would love for this to be a simple home fix for people, but to fit this part to the Gen 4 motor does require a full strip down because the crankshaft must be removed and this cannot be done until the PCB, transfer gears and electric motor have been removed. This would probably be ok for a few, but it would be a nightmare for many.

*Cracks knuckles*

 

[Bearing Man]

Appreciate the effort . Hopefully this solution is successful and can be applied to other motors as well.
Just a few questions regarding the Bosch Gen4 CX bearing seals??:

-Would this replace the current bearing seal kit available from Bosch or would it be an additional component (if you know what I mean).

-Are you developing a better crank shaft bearing that would prevent water ingress?

I understand if you’re not able to provide details (patent reasons), but I look forward to any improvements for the water ingress issue on this motor. These motors are getting better each year and you’re probably seeing issues that the engineers overlooked or never expected.

On a side note; I’m probably the “poster-boy” for motor abuse, but I’ve been lucky for the past 4 years. I try to service what I can but it’s difficult to avoid the daily washing, occasional submerging, types of weather, etc, but I make a conscious effort to maintain correct cadence and not “clunk” the crank. Not sure what else I can do?

Anyways, I’m glad you have a “rescue-room” along with possible solutions.

No, the Bosch bearing shields are working quite well. Unfortunately this is not where the water is coming in. The water is traveling between the crankshaft and the freewheel sleeve (the thing the front chainring is attached to). Once water gets in here, it rusts the crankshaft which quickly wears the plastic crankshaft bushes, this lifts the seal further off its seat allowing more water into the motor. This is why the crankshaft in my earlier pictures looks like it does. And this is what we have stopped happening.

 

[RustyMTB]

On that basis, Pete, do you think there is any mileage in running a bead of some kind of sealant between the crank & the freewheel sleeve as a temprary lash up or is that a monumentally stupid idea?

...I do realise I'm asking a guy who makes a living fixing motors for tips on how to avoid having to have a motor fixed

 

[Bearing Man]

If you flick that white plastic washer out the way, pack a bit of green grease behind it and refit, it may help a bit. Don't get any grit in their though.

 

[RustyMTB]

Just ran out & did that. The white seal is very loose behind its circlip & with the pedal reinstalled, you can see just how much of a vulnerability that is in there.

 

[Stihldog]

If you flick that white plastic washer out the way, pack a bit of green grease behind it and refit, it may help a bit. Don't get any grit in their though.

That’s a really good tip . Easy to do when/if you install the bearing seal shield kit and green grease. (Mmm…green grease )

 

[Tony4wd]

Did one of our bikes today, already some dirt behind the very loose plastic washer. I cleaned it out with a Q-tip and pick. The plastic seal behind the washer looks in good shape so hopefully not much contamination has occurred.