Rear Brake Caliper Piston Won’t Go Back In: Causes And Solutions

Rear brake caliper piston wont retract any advice? More info in
Rear brake caliper piston wont retract any advice? More info in from


Dealing with a rear brake caliper piston that won’t go back in can be frustrating and time-consuming. However, understanding the causes and finding the right solutions can help you resolve this issue efficiently. In this article, we will explore some common reasons why the rear brake caliper piston gets stuck and provide effective solutions to overcome this problem.

1. Rust and Corrosion

One of the most common causes of a rear brake caliper piston not retracting is rust and corrosion. Over time, moisture can seep into the brake system, leading to the formation of rust on the piston and caliper walls. This rust can cause the piston to seize up and prevent it from retracting properly.


To address this issue, start by thoroughly cleaning the caliper piston and caliper walls using a brake cleaner. Next, gently sand the piston and caliper walls to remove any rust buildup. Apply a thin layer of high-temperature brake grease to prevent future rust formation and ensure smooth piston movement.

2. Brake Fluid Contamination

Contaminated brake fluid can also contribute to a rear brake caliper piston not retracting. Over time, brake fluid can become contaminated with dirt, debris, and moisture, leading to the formation of sludge that hinders proper piston movement.


The solution to this problem is to bleed and flush the brake system to remove the contaminated fluid. Start by removing the old brake fluid from the master cylinder reservoir and replacing it with fresh fluid. Then, bleed the brake system to remove any trapped air and contaminated fluid. This process should help restore proper piston movement.

3. Worn or Damaged Caliper Seals

Worn or damaged caliper seals can also cause the rear brake caliper piston to stick. Over time, these seals can deteriorate, allowing brake fluid to bypass and accumulate behind the piston. This buildup can prevent the piston from retracting smoothly.


If you suspect worn or damaged caliper seals, the best solution is to replace them. Remove the caliper from the brake assembly and carefully disassemble it. Replace the old seals with new ones, ensuring a proper fit. Reassemble the caliper and reinstall it, making sure to bleed the brake system afterwards.

4. Incorrect Piston Resetting Technique

Using the wrong technique to reset the rear brake caliper piston can also lead to difficulties. It is essential to use the correct tools and follow the proper procedure to ensure the piston goes back in smoothly.


Refer to your vehicle’s repair manual or manufacturer’s guidelines for the correct piston resetting technique. Typically, you will need a piston resetting tool or a pair of pliers with the appropriate adapter. Follow the recommended steps carefully to reset the piston without damaging it or the caliper.


If you encounter a rear brake caliper piston that won’t go back in, it’s crucial not to ignore the issue. Addressing the problem promptly can prevent further damage to the brake system and ensure your safety on the road. By understanding the causes and employing the appropriate solutions, you can overcome this challenge effectively.