The original problem I had was that I’d get a lot of steering wheel shake when braking and then a sort of throbbing sensation when driving around 50 to 70mph or so. That was a bit concerning, so, I decided I needed to do something about it. I thought it would probably be a warped disc or contamination of the disc from the pad due to lack of use. However, it turned out to be a partially seized caliper.
The Brembo calipers have 4 pistons, the two at the top are slightly larger and one of these was sticking. I managed to get all the pistons out and used a rebuild kit to replace the seals and fit new pistons. I thought it would be an easy job to refit and bleed through using my usual method of using an Eazibleed kit, but I just couldn’t get all the air out and at this point you started wondering if the master cylinder has failed in sympathy. I checked a few forums and did find some interesting advice to tilt the caliper so the bleed nipple is uppermost- see picture – but this still didn’t help. One thing that I never realised - and I’ve owned the car a few years - is that these calipers (front and back) all have 2 bleed nipples. One is obvious to see, but the other one tends to be out of sight. This made no difference though.
Eazibleed – messy, but one man
- 2 ways: either fluid in the bottle of without and use to pressurise the fluid in the reservoir. Use PTFE tape around the threads otherwise the fluid leaks and trickles down the inner wheel arch whilst removing the paint.
Vacuum bleed – could be good, but draws in air through the threads and so is mis-leading
Gravity bleed - assuming reservoir is higher than nipples, then open nipple and wait…and wait - takes too long
Pedal bleed – needs extra person, but best method and ‘as per the workshop manual’
One way valve attached to tube from nipple – possibly OK, but can’t see bubbles coming out from one’s position in the driver’s seat.
Tips
2 bleed nipples per caliper
Undo bolt and tilt caliper so nipple is upmost
Brakes are diagonal dual circuit, so should only need to bleed diagonals - if only working at one corner, such as swapping a caliper
Once I got an assistant to press the brake pedal, the air finally came out after a few strokes. There was so much, it came out as foam for a couple of strokes, so at that point it was obvious it was problem solved.
So, the conclusion is that nothing is as good as a pedal bleed.