Rear brake caliper piston problem

[legepe]

Hi everyone
I have a problem with the rear brake caliper piston
I was using a wind in tool (see attached pic) and could not get it to move, so I used a pair of mole grips and managed free it by turning it back and forth, but while doing this, it has pushed the piston out, dont know why its done this because I wasnt turning it just one way
I know the seal is missing, and I have a kit to replace it, but for the moment I just want to push this one back in and dont understand whats stopping it
Any advice very much appreciated
legepe

[brodfather11]

I believe that the rear caliper piston screws back into the calpier. It will not push in.

There is a large screw in the centre which is worked by the h/brake. When you used mole grips you probably screwed the piston out.

[jj9]

You could have the remains on the dust seal (the seal that is missing) still in place which is jamming the piston somehow.

The piston should push in by hand past the fluid seal (the square cut seal that fits into the groove in the bore of the caliper) Once the piston is in past the fluid seal it should screw in (clockwise) easily with the tool you are using.

.

[shtu]

Looking at the state of that piston, I'd probably bin and replace it.

You can buy brand new ones from not-awful brands (Febi) for £35-40, decent-looking used ones about £20.

[evdama]

Looking at the state of that piston, I'd probably bin and replace it.

You can buy brand new ones from not-awful brands (Febi) for £35-40, decent-looking used ones about £20.

Were you using the correct tool?
The b9 piston winds back clockwise.