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Discussion Starter #1
I decided to change the brake fluid on my 2010 R1200GS while waiting for the weather to improve here in Bilghty.
Coming from a Guzzi background while doing the brakes I decided to do the clutch at the same time.
Big mistake. I soon realised, but too late that the clutch system requires a special minerial fluid and using DOT 4 will ruin all the seals.
I rang my local BMW dealer who wasn't too confident permanent damage hadn't all ready been done but offered to sell me the correct fluid in the forlorn hope a quick flush may save the day.
After a 90 minue round trip in the car to the dealer I set about flushing the clutch system with the correct fluid and eventually managed to get the cluch to operate. The DOT 4 had been in a about three hours.
Only time will tell if it is a permanent fix or not, if problems do arise it is a strip down and all new seals probably by the dealer (ouch).

Stupid mistake not to be repeated but be warned all you home mechanics.
 

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Discussion Starter #4
The mineral oil is a generic type but is not readily avaible where I live. i did enquire at the local car parts store but nothing came up on their data base. Apparently it is used in mountain bikes but try finding it in a rush, not so easy.

I have now spent a bit of time researching the problem. It seems there is conflicting opinions (isn't there always). One study found mininmal seal swelling if soaked in DOT4 so maybe threre is hope.
The bad news is there is no rebuild kit and a new master and slave cylinder would be needed.

24 hours later the clutch is still working, watch this space.

As a side note. I was dicussing the issue with my wife and she asked what would happen if a problem occured in a remote area (adventure bike?). I suggested the odds are extremely small on getting hold of the correct fluid, silence followed.
 

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Discussion Starter #5

This guy has done a useful test on changing mineral fluid for DOT 4 on bicycle brakes.
Shimano (the brake he is using) were the leaders in the use iof mineral brake fluid and state that DOT fluids will ruin the seals.
What I am sure of is exposure to DOT 4 over a few hours will not disable the clutch, which I was told would happen by my local BMW dealer.
Maybe long term there could be a risk of probelms but the YouTuber gave it a couple of months and the brake still worked.

Most people will never encounter this problem because apparently BMW do not recommend changing the fluid at all.
 

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I agree with your wife, seems strange to have such a "unique" fluid should you have a failure out in the wild. I wonder if a standard hydraulic oil or engine oil could work...
 

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Discussion Starter #7
The problem with this 'new' mineral brake/clutch fluid is that there is very little information published on it. There is also different types with conflicting articles on whether they are compatibale with each other.
If it had been engine oil the internet would be ablaze with indignation and the threat of legal action etc.
I still find it hard to believe BMW don't supply a seal kit for the clutch master and slave cylinders but then in a weird weary way I'm not at all surprised.
 

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Discussion Starter #9
Correct, in theory you can leave minerial fluid for a unspecified period. So unless there is a problem no action needs to take place.
But the system is not a sealed unit so at some stage the fluid may need topping up or changing so a issue may arise.
 

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When I had to replace a leaking clutch cable on my 09 I did a lot of digging to make sure a got the correct mineral oil per BMW spec. found this at a local bicycle shop
 

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Discussion Starter #12
Thanks for the suggestions.
There is not a spec sheet for the BMW fluid (or any other I can find) so it is difficult to know what is actually in the bottle. I did contact BMW UK and Germany and drew a blank, just to know the type of seals installed would be a help to determine compatable fluids but BMW won't play ball on that either.
 

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Correct, in theory you can leave mineral fluid for a unspecified period. So unless there is a problem no action needs to take place.
But the system is not a sealed unit so at some stage the fluid may need topping up or changing so a issue may arise.
You should never need to top the clutch master cylinder up at all. The fluid level actually rises as the clutch wears, and not fall.
 

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I'd never bled an hydraulic clutch before and did it on another bike I have this week. Ended up just rebuilding the master and reverse bleeding it to get it back to better than new. The clutch master is a pretty simple bit of kit and easy to disassemble, install the new plunger and seals, and put it back in service. Nothing to be afraid of if you have the right tools (big syringe mainly).
 

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Discussion Starter #15
Thre is no rebiuld kit for the mineral fluid BMW clutch system.
I used a big syringe to reverse bleed my clutch when changing to the correct fluid, it is the recommended method in the Haynes manual.
 

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Not sure what the requirements would be here but "mineral oil" is just single weight oil from the ground and not from (vegetable) plants. Some heavy machinery that I am familiar with specify mineral oil for the brakes which is further specified as 15 weight motor oil. (no additives, not synthetic)
 

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You can get mineral oil in a grocery or pharmacy, it is food grade so should be good to go. It at least would do till you got the right spec fluid.
 
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