[bradical]

I recently bought some used Shimano XT (756) 8" brakes from a friend. They worked very well up until very recently (ridden for 3 weeks?) The front lever has started to feel mushy and has very little feel or power. They feel good again if you pump them up for quite a bit. So it sounds as if I need to get it bled.. right?

The part that I'm confused about is this change happened almost over night. No gradual loss of feel or power, now the lever has started pulling almost to the bar. There are no obvious leaks or loss of fluid. However, the weather has gotten bitterly cold here (for reference: bitterly cold in SC=in the 20's). Is mineral oil affected by cold weather? I'm hoping that's all, but the rear brake still feels perfectly fine. The brakes were shipped to me in a little e13 box, and the front line looks like it got crimped from being in the small box. For a day or two after I set them up, it wept a small amount of fluid where the lever meets the line (right where it was crimped). After a day or two of riding, the weeping of fluid stopped and the brakes felt great.Could the cold weather amplify the effects of the small loss of fluid?

Please help, I'm not quite sure of what to do...
Thanks

 

[DßR]

actually if you have to pump it up and then it feels great, my experience is usually that that means you are low on fluid. Which seems to make sense since you lost some.

Try topping the resi. off with mineral oil, might as well give it a bleed while you're at it since they're easy as crap to bleed.

As for the cold weather, I have no idea. Shouldn't really have an effect. Sometimes though, the fluid leaks between the inner housing and outer housing on your hydro line, so you may have lost a lot more fluid than you think.

 

[bradical]

Thanks. I opened up the res and sure enough I was low on fluid... especially since the shimano manual says it should be overflowing when you put the little rubber hat cover back on. It was still about 1/2 or 1/3 full. Since fluid was always covering the hole, theoretically, I didn't get any air into the system and won't have to bleed them (at least right now)?

Going on some e-advice from matt, I squeezed the lever a couple times and a few bubbles came out, and then no more bubbles. The lever feels great and like it was just bled now. I still need a top off right?

 

[me89]

it might be a good idea to replace the line too man it would hurt but then you would have to bled them and replace the fluid but just a thought from a fellow rider. i dont think you want to ride averies without a front break like vince did.

 

[OGRipper]

You basically describe the ghetto method of bleading that I've used on mine with great success. Just pop the cover, squeeze the lever a few times, then squeeze and hold the lever while you tap the line, and soon enough whatever air is in there will float out. Then just top em off and you're good to go. No idea about the cold though.

Since you bought em used and the line is leaking, I suggest that you just go ahead and replace the line. It's a good idea to replace the fluid in any hydro every year or two anyway, it can get contaminated over time and help cause a mushy feel. Same as you'd probably replace cables on a used set of cantilevers...

 

[Rik]

I would've thought, first thing to do when buying used components such as brakes, is give it a full strip down, replace the lines and pads, then give it a bleed... same as I always put new seals and rebuild a fork when I buy 2nd hand, that way you know it's going to perform reliably from day 1.