Author Topic: Clutch fluid problems  (Read 275 times)

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Offline stevel

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Clutch fluid problems
« on: April 24, 2018, 07:32:08 pm »
Hi everyone,

Theoretical question: What would happen if someone put the wrong fluid (DOT4) in a K1300S clutch?

Has anyone done it? What were the symptoms, if any?


2nd question - assume that someone has done the above, what is the best way to flush it all out before starting again with the right stuff?


Thanks folks.

Steve

Offline TomL

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Re: Clutch fluid problems
« Reply #1 on: April 24, 2018, 10:20:48 pm »
Depends how long the wrong fluid had been in there.
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Offline stevel

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Re: Clutch fluid problems
« Reply #2 on: April 25, 2018, 07:27:46 am »
Not sure how long it has been in there, if indeed it is the wrong fluid. I'd guess around 6 months, but the bike was off road for the vast majority of that time, so it hasn't covered many miles in that state.

Offline MadMountainbike

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Re: Clutch fluid problems
« Reply #3 on: April 25, 2018, 12:58:30 pm »
Could be a big problem if left. The clutch uses mineral oil not DOT fluid. It needs cleaning out straight away otherwise it'll damage all the seals and hoses from the lever to the slave.

The only real way to clear would be to get a couple of bottles of Hyspin in just keep flushing it through the system.
« Last Edit: April 25, 2018, 04:14:58 pm by MadMountainbike »
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Offline TomL

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Re: Clutch fluid problems
« Reply #4 on: April 25, 2018, 11:21:47 pm »
You will know if the wrong fluid was used if it leaks or does not operate correctly.
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Offline Andym535

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Re: Clutch fluid problems
« Reply #5 on: April 26, 2018, 07:45:07 am »
The question that springs to mind is, of course, "Why have BMW used a different fluid for the clutch?" And how does the fluid level rise as the clutch plates wear?

Offline Phmode

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Re: Clutch fluid problems
« Reply #6 on: April 26, 2018, 08:19:44 am »
Fluid level rises?

Offline Andym535

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Re: Clutch fluid problems
« Reply #7 on: April 26, 2018, 09:53:38 am »
RTFM... Page 87, or there about but that may depend on version of the manual.

Offline Ady00

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Re: Clutch fluid problems
« Reply #8 on: April 26, 2018, 11:29:02 am »
Clutch fluid rises on the 1100/1150 twins due to how the piston lifts the clutch on these models as the clutch wears the piston comes back not further out as a lot of people think so if ignored or you brill the system you end up with hydraulic lock don’t know what system our K’s have will look into it

Offline Phmode

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Re: Clutch fluid problems
« Reply #9 on: April 26, 2018, 12:03:07 pm »
p109 in mine!

How weird is that. I guess my clutch has never worn  ;D

Offline Andym535

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Re: Clutch fluid problems
« Reply #10 on: April 26, 2018, 12:36:55 pm »
It must be because the clutch actuator pushes against the compression springs in the clutch to separate the plates, which means as the plates wear the springs can push fluid back up the line to the reservoir. Maybe all clutches do that, but only BMW clutches wear enough to notice a fluid rise.

Offline Phmode

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Re: Clutch fluid problems
« Reply #11 on: April 26, 2018, 01:14:14 pm »
Most car systems (used to) operate by the slave cylinder pushing on the end of a fulcrum arm which is what pushed the release bearing 'in' against the pressure plate springs. This meant that as the plates wore the inward motion of the inner end of the fulcrum arm in reversedat the other end of the arm so the slave piston always moves 'inward' meaning the clutch fluid at the master cylinder drops.

The big exception to this in my world was my SAAB 9000 Turbo. In this otherwise conventional set up the slave cylinder was inside the bell-housing and pushed the fulcrum arm from the other end.

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Offline Andym535

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Re: Clutch fluid problems
« Reply #12 on: April 26, 2018, 07:10:33 pm »
Still don’t see why they use mineral oil instead of DOT 4 or 5.1

Offline Phmode

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Re: Clutch fluid problems
« Reply #13 on: April 26, 2018, 07:56:46 pm »
The main reason is that unlike DOT fluid which is hydroscopic (it absorbs water from the atmosphere, thus lowering the boiling point of the fluid) Mineral oil is hydrophobic (it does NOT absorb water from the atmosphere so it's boiling point remains constant).

Of course, this is only true if water can never enter the clutch/brake system. If water does enter the system on a K clutch, then the water is not absorbed by the fluid but rather sinks to the lowest point of the system which is normally the clutch slave cylinder (as in our case) which also happens to be the hottest part of the system.

So, if this water gets hot and boils, the air given off reduces the effectiveness of the clutch hydraulic pressure system. It might also mean that the water will boil out of the system...

It also means that it is easy to remove any water by a partial bleed of the system, so removing any fluid at the lowest point.

Offline Eyore

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Re: Clutch fluid problems
« Reply #14 on: April 26, 2018, 08:55:31 pm »
Could be a big problem if left. The clutch uses mineral oil not DOT fluid. It needs cleaning out straight away otherwise it'll damage all the seals and hoses from the lever to the slave.

.

Really?
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