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40. Brake and Clutch Bleeding

In preparation for Clutch and Brake bleeding, I had previously measured the bleed nipples with vernier callipers in order to find the best diameter pipe. Unfortunately I found that the Clutch is different from the Rear Brakes which are different from the Front Brake nipples! I therefore elected to buy a Bleed kit which contains a short section of silicon pipe fitted with a neoprene sleeve on one end and a non-return valve on the other end. The former meant that it could be fitted to any size of bleed nipple, and the latter meant that it was not necessary to submerge the end in a jam jar of brake fluid to prevent air from being sucked back into the system.

Since I was attempting to do this on my own, I also elected to use a bleed pump that pressurises the system to force the brake fluid through, rather than has a second person to pump and release the pedal.

Although the Clutch bleed nipple extends above the Bell Housing, it is still in a very inaccessible area. Getting a bleed pipe and ring spanner fitted over the bleed nipple and in such an orientation to allow the spanner to be moved took some trial and error. I found that I could hold the bleed pipe in position with my right hand approaching the nipple from directly above; whereas my left hand had to work under the submarine plumbing to get to the ring spanner.

Clutch / Brake Fluid used, Bleed Pipe and Ring Spanner in position ready to bleed

With the neoprene sleeve safely fitted to the Clutch nipple, I was able to bleed it successfully. However, the non-return valve was actually jammed shut, and therefore when I removed the neoprene sleeve, the silicon tube was under pressure and subsequently squirted some Dot4 fluid down onto, and into the Bell Housing. I cleaned this up but later found that the fluid was seeping out of the gap between the Bell Housing and Dry Sump Guard. The latter was removed and the whole area was thoroughly cleaned which took some additional time.

Before filling the brake system with fluid I decided to first pressurise it with air from the bleed pump. It was taken up to only 10 psi but then left for several minutes to see if there was any drop in pressure which would indicate a leak in the system somewhere. This was helpful because I quickly discovered a leak at the rear right hand side calliper junction. Tightening the connector and re-pressurising, the pressure remains stable.

Two rounds (Rear LHS, Rear RHS, Front RHS, Front LHS) were performed and the brake pedal felt firm - but not quite firm enough. A further two rounds using the traditional method of dressing the pedal, releasing the nipple, re-tightening and releasing the pedal were performed - but no significant increase in pedal firmness was achieved.

Brake bleed kit in position for front callipers

When I did revisit the brakes, it was with a Sealey brake bleeder pump. As a piece of kit to be used in regular maintenance this, or similar, is highly recommended. As a first trial and to satisfy myself that I wasn't dealing with a leak in the system, I connected the pump first with no brake fluid in it - and then pressurised the system to 2 bar. I left it for a couple of hours and then returned to see that the needle on the pressure gauge had not moved. With that done, I knew I was just chasing bubbles in the system. A little persistence and allowing plenty of fluid to run out of the rear bleed nipples in particular produced great results.

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