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PostPosted: Wed Aug 14, 2013 8:20 pm 
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Location: The land of Lea & Perrins
OK, so this is a bit of an odd one.

I've got some XTR M975 Disc Brakes, and the right hand (front) brake lever leaks fluid of some description. At first I thought it was a case of having to replace the seals (can you even do that with Shimano brake levers?). However, I went out to the shed tonight to take a couple of pictures of the leaky lever, and it's since occurred to me that there is no reason for brake fluid to be leaking out of that particular point on the lever, as there is no seal there. The area where it is leaking is where the little piston is attached to the lever blade (at the opposite end to where the seal would be), and I can't work out why it's leaking there?

There is a tiny amount of play in the lever blade itself, and when I 'wiggle' the lever I can get the fluid to leak out, as shown in the 2 photos below. The lever blade is a separate entity to the rest of the lever body, and I can't see any signs of leakage around the reservoir seal (at the other end of the piston) or on the piston itself.

The brakes were freshly bled before I bought them, and they don't appear to be feeling any different - the lever doesn't seem to be moving any further than normal when the brakes are applied. I'm confused. Any suggestions?

Before wiggling the lever:

Image

After wiggling the lever:

Image

Note that when I wiggle the lever, I'm NOT applying the brakes, so the little piston isn't moving at all - just the lever blade is.


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PostPosted: Thu Aug 15, 2013 12:27 pm 
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I still think it could be that there's some fluid under where the lever is connected to the body. The fluid looks old and grubby. Bring it over when you bring the forks. We'll have a shufty. Shimano Mineral oil is a pinky colour when it's clean.


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PostPosted: Sun Aug 18, 2013 4:44 pm 
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I had the same problem on my old set the rubber seal was perished on the lever housing.

In the end I changed both levers to the xt type never sorted the leak out after sending it away for new seals.

Pity there nice brakes are yours the old IS mounts


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PostPosted: Mon Aug 19, 2013 8:45 pm 
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racefacecannondale wrote:
Pity there nice brakes are yours the old IS mounts



the majority were IS mount but you do once in a while come across post mount XTR callipers.

re: leak there may be fluid on the pivot but if you can consistently make it appear after wiping it away, the it has to be the piston seal.


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PostPosted: Mon Aug 19, 2013 8:48 pm 
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02gf74 wrote:
racefacecannondale wrote:
Pity there nice brakes are yours the old IS mounts



the majority were IS mount but you do once in a while come across post mount XTR callipers.

re: leak there may be fluid on the pivot but if you can consistently make it appear after wiping it away, the it has to be the piston seal.


Thanks for the info guys. So is there a seal on the lever blade end of the piston aswell then? This is my first set of Shimano discs - I've read that spares aren't available for them, so they have to go back to a shop to have any work carried out. Is that right?


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PostPosted: Mon Aug 19, 2013 9:03 pm 
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not sure what you mean by that.

shimano tech doc does not show the psiton/seal arrangment
http://techdocs.shimano.com/media/techd ... 728273.pdf

look at LH lever - you can see the theaded part of the piston sticking out of the lever body - I expect there is a rubber dust seal plus there will be seals on the piston plunger itself.


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PostPosted: Mon Aug 19, 2013 9:06 pm 
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The fluid is coming from where number '8' goes into the lever blade (the bit you pull with your fingers).

I think that qualifies as the least technical explanation ever.. :oops:


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