Rear Caliper Pistons

[MatthewH]

For future reference, once the motor has been wound back (either using VCDS or using a T40 torx bit on the back of the caliper with the motor removed), the piston can just be pushed back without turning. The replacement caliper arrived today and I used a 150mm G-clamp to push the piston back. I'll be fitting the new caliper to the car in the morning.

[MatthewH]

I've just finished fitting the replacement caliper, pads and discs to my car. A fairly easy job overall, most of the time was spent cleaning up the replacement caliper.

I've cycled the handbrake a few times and it sounds correct now (the first few times took longer than usual as expected). However, with the handbrake off and the transmission in neutral, I can't spin the brake disc (it's still jacked up off the ground).

I don't know much about the Quattro system in these cars - if the other wheel on the rear axle is on the ground, does the differential have some sort of lock that would prevent the jacked-up wheel from spinning? Or should the wheel spin freely? It feels as though the handbrake is not disengaging but it sounds like it's working correctly.

I've left it as it is until the morning. I'm hoping the new caliper is not at fault!

[Mechcanico Lee]

With permanent 4 wheel drive systems you do tend to get some diff bind so makes the brakes feel like they are stuck on somewhat

[MatthewH]

Thanks Lee, hopefully that's all it is. I'll put the wheel back on tomorrow and give it a try.

[MatthewH]

Piston is still seized unfortunately. I put the wheel back on and drove down the street and back. The caliper was smoking and it didn't feel right to drive.

The sliding pins were moving freely before I put it all back together. Seems as though the piston on the new caliper is also sticking for unknown reasons. Brake lines looked OK to me.

[MatthewH]

Just finished rebuilding my original caliper. I cleaned up the piston, and replaced the main seal and piston dust boot. It's now moving freely as it should. I'll be rebuilding the caliper on the other side soon too so they're in sync - that side also felt stiff when I replaced the discs and pads but wasn't completely seized.

If anyone's interested I can post a guide for this process, including photos and part numbers.

[1781cc]

Yes please! good to have for future

[onetwentie]

Originally Posted by MatthewH

Just finished rebuilding my original caliper. I cleaned up the piston, and replaced the main seal and piston dust boot. It's now moving freely as it should. I'll be rebuilding the caliper on the other side soon too so they're in sync - that side also felt stiff when I replaced the discs and pads but wasn't completely seized.

If anyone's interested I can post a guide for this process, including photos and part numbers.

MatthewH - Are you saying then that the problem was just the piston, and the new seals fixed the issue? was that the original symptom, that the caliper wouldn't move in or out?

I wonder if that was the issue with the replacement which you purchased too?

Out of interest, what led you to try the seals? was it self diagnosis??