guadzilla

Hi guys -

So apparently my Di2 shifter has a leak coming from what appears to be the piston (see attached photo).

Sequence of events:
- Bled the hoses
- Changed the brake pads on the bike
- Used the flat of a screwdriver to separate the pads

After that, a drop or two of oil starting coming out from the shifter. Prior to this, it was working perfectly.

Any ideas on a solution?

Amt0571

I've had his happen with MT520 brakes, SLX brakes and SRAM Rival HRD brakes.

In the three cases fluid came out when separating the pads, but once the brake was properly bled and new pads were mounted, there was no leak.

I concluded that they were overfilled and when separating the pistons, the excess fluid came out somewhere. I'm not sure if they have an overpressure valve or a similar mechanism, or it simply leaked through the piston seals, but I can assure you that after months of riding there was no visible leak.

After that, when I replace the pads at home I remove the lever reservoir screw and attach a syringe there. It makes it easier to separate the pads. Then I bleed the brake, and install the new pads.

The bleed on Shimano brakes is so quick that it's totally painless and a breeze to do.

guadzilla

Thanks! Will give it a go tomorrow....

cxwrench

You want to start the process by pushing the pistons all they back into their bores, not end it by doing that. There is obviously (or maybe not so obviously) a given amount of brake fluid that will 'fit' into the system. If you bleed first then push the pistons back you'll exceed that. Most bicycle brake systems will have a vent hole for when this happens.

guadzilla

Makes sense. I actually had a friend helping me out with this, and I dont remember whether the pistons were in or out when he did the bleed. It is comforting to know that there is a good chance that the shifter is not actually damaged.

Amt0571

I'm betting the shifter is OK. If you did the bleed without retracting the pistons first, the system probably ended up overfilled.