I have a set of M785s and they have been pretty well behaved for the 2 1/2 years I have had them but the front is now causing me no end of grief.

It keeps sticking on or going completely limp when the bike isn’t being used. I stripped the whole thing down a couple of weeks ago and it started to behave better but its been back to its old tricks. I put the bike away and its perfect I go for a ride a couple of days later and the brake is jammed on. I push the pistons back and the n when I try and pull the lever it goes back to the bar. I then go through the rigmarole of a bleed and its fine.

I left it with the lever tied to the bars last week and then rebled last night and my ride this morning was perfect. Then just got the bike out of the car. Refitted the front wheel and its jammed on. Is there something I’m doing wrong or are they goosed?

Forgot to say I think there might be a leak at the reservoir but possibly only after I separate the pistons…

Just buy a new lever?

Are you sure the lever is leaking?

With the pistons out you are fully bleeding the system. Then when you push the pistons back the excess pushes out through the reservoir and out through the overflow.

Sounds to me like you have sticky pistons. When you cleaned them did you add any lubricant?

One way to tell if you need new brakes is to swop the calipers over. If the back caliper which is fine still does it on the front them it’s the leaver.

If the front caliper does it on the back then it’s the caliper.

Good luck

I’ve seen similar problems like this in the past with an older pair of Shimano brakes.. the old removable reservoir cap design.

It turned out that there was a split in the reservoir cap which wasn’t immediately obvious. Sometimes it would be open to air and the lever would be limp, then other times the split must have been air tight and the brakes felt fine. Check your master cylinder for damage and perhaps replace the lever?