Rear brake piston - dust boot replacement?

Angus · Post by **Angus** » Tue Jul 01, 2014 11:16 am

How easy it is to replace just the dust boot on a rear brake piston?

I'd really, really, like to not remove the piston completely. Brakes are working fine, but I ripped the rubber winding the piston back in - it was turning with the piston (corrosion in its seat, I guess) and eventually tore. Had to do it, because I need the car on the road.

Is it possible to wind the piston out enough to give it a bit of a clean up and replace the dust boot?

Post by **Merlin** » Tue Jul 01, 2014 11:21 am

It is simple but I wouldn't describe it as easy. Getting the boot back into the groove is tricky.

Pump the brake pedal a few times to push the piston out a bit. Make sure not to pump it out too far or it will be a a right PITA to get it back in. Clean up the piston, put the new boot on, wind it back in and try and get the lip of the boot back into the groove on the caliper.

Angus · Post by **Angus** » Tue Jul 01, 2014 1:26 pm

Splendid. Thanks.

When you say push it out "a bit", how far is too far? I've never seen a piston out of a caliper so I've no idea how long they are ...

Post by **Merlin** » Tue Jul 01, 2014 1:46 pm

It is a good couple of inches. What I mean by too far is that if you are using a piston wind in tool you need a certain amount of space to get the tool in-between the caliper and the piston. If you pump out the piston too far there isn't enough room to get the wind in tool in place. I accidentally did this first time and it took me ages to get the piston back in enough to use the tool.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Tue Jul 01, 2014 1:52 pm

Merlin wrote:Getting the boot back into the groove is tricky.

This ^^^^

With the piston still in the caliper, I've given up trying before (on a Sunny, not a lude).

Angus · Post by **Angus** » Wed Jul 02, 2014 1:06 pm

I foresee some excellent entertainment at the weekend, then.

Perhaps even more fun than a whole afternoon trying to get a stuck sliding pin out a couple of weeks ago. (soaking it in a tub of diesel eventually helped, and good job I had a spare pin in my toolbox following the dreadful thrashing the stuck one took ...)

Sounds like a plan to have someone hold the rewinding tool in place in the caliper whilst pumping the piston out to stop it going too far ...

Post by **Merlin** » Wed Jul 02, 2014 1:08 pm

The threat of pushing out the piston is only there if you go gung-ho on the brake pedal. Pump it one at a time and you'll be fine. You only need to get the piston to move about an inch and you will have plenty room to do every thing you need.