Author Topic: Water pump oil leak  (Read 7181 times)

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Offline KennyV

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Re: Water pump oil leak
Reply #80 on: September 21, 2020, 07:55:15 PM
Thank you!!!!
71 Z50 Minitrail, 72 Yamaha RT2 360, 74 Yamaha DT250A, 20 CB500X

Offline Halfricatwin

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Re: Water pump oil leak
Reply #81 on: September 21, 2020, 09:21:07 PM
Hey Timur - How is your water pump doing these days following the 2019 rebuild?

Regards the water pump drive shaft:  Is there much in the way of an unsupported length of this shaft before the point it meshes with the oil pump shaft - if so, what kind of distance (approximately) are we looking at?  Thanks.

Offline timur

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Re: Water pump oil leak
Reply #82 on: September 21, 2020, 09:46:21 PM
*Originally Posted by Halfricatwin [+]
Hey Timur - How is your water pump doing these days following the 2019 rebuild?

Regards the water pump drive shaft:  Is there much in the way of an unsupported length of this shaft before the point it meshes with the oil pump shaft - if so, what kind of distance (approximately) are we looking at?  Thanks.
When my OEM pump failed I bought new one and replaced the leaky one because I need my bike to go to the office. Then it took me about one month to gather all the info about possible replacement parts. Finally I disassembled the OEM (leaky) pump and repaired it but couldn't test it yet. So my repaired pump is stored and awaiting its moment while my bike runs with new one. The final part is lacking - the proper test. If one day I need to replace water pump the repaired one will be used.

Regarding the distances - unsupported length is 55mm, supported 40mm.

Regards

Offline Neox

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Re: Water pump oil leak
Reply #83 on: September 21, 2020, 11:12:25 PM
I decide this afternoon to have a more precise idea of the situation...
After some disassembling...

There is trace of dry cooling, red arrows. But it seems old, not recent. On the right it's grease from the chain. Now i use oil, so grease leak down...


Dry cooling and dry oil on this picture. But old too.


Another view...
Near the junction oil pump/water pump there is oil, but more dry than wet.

I think it's not leaking now, the traces are old, they probably come from the running-in process.
The water level was at the midle, i put it at the max.

for the moment I am rather reassured, it's not what I feared with my habit of buying the stuff assembled on a Monday morning...

Offline Neox

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Re: Water pump oil leak
Reply #84 on: September 21, 2020, 11:16:32 PM
I didn't put the fairing of the lower engine back up after cleaning, just to check the evolution over the next few kilometres.

Offline Halfricatwin

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Re: Water pump oil leak
Reply #85 on: September 24, 2020, 07:19:10 PM
Timur - thanks for those measurements. I've been pondering the design of these water pumps and looking at the drive line that serves them. Just me speculating here but, given the relatively crude joint (single slot type) where the water pump shaft mates with the drive from the oil pump, added to that 55mm of unsupported shaft (and possibly more on the oil pump side) you mentioned seeing from your strip down, suggests to me that some of the purely rotational aspect of the pump shaft could become compromised by the introduction of an elliptical moment -  maybe this is what is negatively affecting the pump seals? Easy to see that slot joint would have been far more radially efficient if it had been a (far more expensive) sleeved spline type instead. Simply put, a pump shaft drive rotating out of plane is going to bugger up one or both of the water pump's internal seals to a greater OR lesser degree depending how bad this runout is. Given the relatively imprecise nature of the slotted joint and some anomaly in the manufacture of the pumps themselves, some bikes will fare better than others.
Last Edit: September 24, 2020, 08:06:47 PM by Halfricatwin


Offline Halfricatwin

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Re: Water pump oil leak
Reply #87 on: September 25, 2020, 12:59:32 AM
Neox - Hard to be definitive without having the two water pumps side by side but on the face of it perhaps, an interesting comparison that better supports the suggestion I was making. Have a close look at the water pump shafts in both schematics. The "old" version shaft looks to be significantly better supported than the new. There's little of it protruding from the pump body.
There is a lot more unsupported shaft visible in the "new". Because the drive is coming from the oil pump on the right side of the case, I believe the eccentric action of the pump shaft is going to be greater at the water pump end of the driveline - so maybe not the best place to remove support.
Honda must have redesigned the new format water pump drive for a reason. I think it's fair to say their design engineers don't do something for nothing. That said, a good example of newer doesn't necessarily mean better or more accurately, "it it ain't broke, don't fix it". How many times have we seen that? If my suspicions are founded in any way at all - and it is a big "if", I don't see Honda rushing in with a recall and mod kit anytime soon.   
Last Edit: September 25, 2020, 01:26:04 AM by Halfricatwin

Offline Neox

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Re: Water pump oil leak
Reply #88 on: September 28, 2020, 01:22:44 AM
*Originally Posted by Halfricatwin [+]
The "old" version shaft looks to be significantly better supported than the new. There's little of it protruding from the pump body.
There is a lot more unsupported shaft visible in the "new".
Yes, on the old pump only the coupling protruded out of the pump housing, which also means that the pump was more embedded in the crankcase.

on the new version, and if you look at the position of the 3 fixing screws on the motor, I think there is a significant risk of misalignment.
the problem would be more related to the coupling than to the shaft, as Timur said the new one requires more machining precision, but honda don't do on all models, irregular quality...

Offline timur

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Re: Water pump oil leak
Reply #89 on: September 28, 2020, 01:42:03 PM
*Originally Posted by Neox [+]
Yes, on the old pump only the coupling protruded out of the pump housing, which also means that the pump was more embedded in the crankcase.

on the new version, and if you look at the position of the 3 fixing screws on the motor, I think there is a significant risk of misalignment.
the problem would be more related to the coupling than to the shaft, as Timur said the new one requires more machining precision, but honda don't do on all models, irregular quality...
It's a classical problem of chain tolerances (accumulation of tolerances in complex assemblies) - in this case the coaxiality of water and oil pump shafts depends on a lot of them. Given that manufacturing imprecisions during machining have normal distribution different methods need to be applied during assembly and manufacturing to guarantee this coaxiality:

1. Improve machining precision - reduce the value of each tolerance (more cost).
2. Reduce the number of tolerances involved at the same time (redesign of the components).
3. Reduce the sensivity of the component to imprecisions - shorter shaft for example.
4. Individual adjustment for each assembly (very expensive). Or components pairing on simple tolerance chains like piston/cylinder for example.

In case of recurrent water pump fails of Yojimg it must this sort of problem IMHO - something must be wrong with the crankcase. I can't figure any other explanation. Usually QC should avoid these things but seems something failed with Honda  :027: