Brake Caliper Repair: How to Repair a Cracked Dust Boot

  • 2-3 hours
  • Advanced
  • 0-100
What You'll Need
Jack stands
Air hose

When you’re undertaking brake caliper repair, one thing you might encounter is a cracked dust boot. This is something you can fix although it will be easier to replace the dust boot rather than try to repair it, as you won’t manage as good a seal with a repair.

Step 1 - Accessing the Caliper

To do this, start by slightly loosening the lug nuts on the wheel where you’ll be working. With that done, raise the front end with a hydraulic jack. Put jack stands under the front axle and remove the wheel. You will now be able to see the caliper.

Step 2 - Removing the Caliper

Take a wrench and loosen the nut that attaches the brake line to the caliper, putting the end of the line into a jar. Use a rag to plug the hole where the line enters the caliper to avoid spilling any brake fluid. Be especially careful with this, as it will damage the car paint. The caliper will generally be held on by two bolts. Remove these and take out the caliper, and watch that the brake lines aren’t twisted.

Step 3 - Accessing the Dust Boot

Put the caliper on a flat surface, with a piece of wood in front on the piston. Attach an air hose to the hole where the fluid enters the caliper. Feed in compressed air. Keep your hands clear. The piston will come out.

Step 4 - Removing the Boot

If the piston won’t come out easily, work it out with your fingers, and you’ll see the dust boot. You need to remove the dust seal and the piston from the bore, and for this you should use something non-metallic.

Once the bore is clear, use brake cleaner or denatured alcohol to clean it out. Make sure you don’t use any petroleum products for cleaning. Be sure you clean out all the dirt, then inspect the caliper. If there are deep scratches in the caliper bore, you’ll need to replace it. Make sure the bore is absolutely clean before you move on.

Step 5 - Replacing the Boot

Use brake fluid to lubricate the parts, and start by working on the seal. It’s important to be sure it’s on the groove properly and not twisted. The boot needs to go into the bottom on the piston. If you twist the piston, this will help seat the boot properly. This isn’t easy, so take your time to ensure it’s done right.

Once it’s seated, check that the piston is square, then use hand pressure to put it in place. There’s a groove at the top of the piston, and you need to work the dust boot into this. To reassemble, reverse the procedures you used to take off the caliper. You’ll need to bleed the brakes before driving the vehicle.