brake bleed

Rear brake bleed and service

One of the MOT failures was “Nearside brake application uneven.” This suggested to me that the brakes needed thoroughly bleeding to remove any air, and the caliper checking to make sure it was moving correctly and applying brake pressure to the disc. Bleeding the brakes is easier if you have a friend to hand. You’ll need an 8mm brake spanner for the bleed nipple. Now these can be very fragile and often snap inside the caliper. Even though they often snap in the closed position it still means you now can’t bleed the brakes. Some people recommend soaking the nipple in WD40 overnight, or ‘shocking’ the nipple loose using a deep socket. Assuming you can free the bleed nipples on all calipers, you should start bleeding at the caliper furthest away from the Master cylinder, then proceed in order, ie. N/S/R, O/S/R, N/S/F, O/S/F. To bleed a caliper, attach a brake bleed kit to the nipple, loosen the nipple and ask an assistant to depress the brake pedal. At the bottom of the pedal’s travel, ask them to hold it there and close the nipple. Release the pedal and reopen the nipple. Repeat this process until only fluid comes out of the bleed nipple and no air bubbles are present. IMPORTANT: Make sure you keep the brake fluid reservoir topped up with fluid. If it drops too low, you’ll draw more air into the system, defeating the purpose of the exercise and you’ll have more work on your hands. You may need to go round all 4 calipers two or more times to remove all the air, depending on how much is present.

With this done, I removed the brake disc and carrier so I could check the movement of the piston. It was very stiff, so I greased the piston lightly and wound it back in. I got an assistant to press the brake so the piston was pushed out and wound it back in again. I did this 3 or 4 times and the piston loosened off nicely so it was moving more freely. To help pass the MOT, I added to new brake pads while I was there. A very easy job – simply remove the clips from the old pads and tap out the slider with a screwdriver. Grease up the slider and replace it together with the new pads. Press the clips back onto the pads and ensure the slider has its retaining pin fitted. Replace the disc and pad carrier and voila.