Audi A6 C5: Why Won't the Rear Caliper Piston Retract?
A stuck rear caliper's piston doesn't always mean you have to replace the whole caliper. This guide will show you how to diagnose it in your Audi A6.
This article applies to the Audi A6 C5 (1998-2004).
The rear calipers are slightly different from the front calipers. Most of the time, when a caliper's piston gets stuck, it means you need a new caliper. However, if it's stuck while you're doing a brake job, then there could be other reasons for that. This guide will help you diagnose this issue in the Audi A6, which will assist you in determining whether your caliper is faulty or you missed a step. Read on to learn how to get this piston back in.
Material Needed
- Rear caliper compression tool
Step 1 – Disengage emergency brake
It could be engaged.
The emergency brake is connected to your rear brake calipers and works by pushing out the piston when you pull the handle. The rear caliper pistons won't decompress if your emergency brake is engaged. Make sure the parking brake is all the way down and disengaged before you try to decompress it. You also may want to check that the cables are free under the car and not rusted or bound up somewhere.
If the parking brake handle is disengaged, proceed to Step 2.
Step 2 – Wind back the piston
Use the right tool to compress the rear pistons.
As we've mentioned above, the rear calipers are different from the front ones. If you're trying to use a regular c-clamp, you are not going to be able to get the piston fully retracted because of their design. The parking brake mechanism winds out the piston in normal use, and needs to be screwed back into the caliper with a special tool before new pads can be installed. You can rent it at most chain auto parts stores. Put a hose on the bleeder screw with the end above the caliper, so the fluid goes up and blocks any air from getting in, and use the tool to wind back the caliper. The tool works by screwing in the piston, while pressing against the other side of the caliper at the same time.
If the piston won't compress, proceed to Step 3.
Step 3 – Replace brake caliper
It could be faulty.
The brake calipers do go bad from time to time, especially if you live in an area that salts the roads in winter, or if you don't flush your brake fluid. If your pistons won't go back in, or they go back in but won't come back out again, then you need a new caliper. You can change the calipers easily, but you will need to bleed the brake system after. See the article: Audi A6 C5: How to Flush the Brake Fluid
Related Discussion
- Rear Caliper Won't Retract - AudiWorld.com
