All Minis are fitted with a brake master cylinder and the vast majority, i.e. those with manual transmission, have a clutch master cylinder too. Both are parts that we tend to take for granted until they go wrong. The design of the clutch master cylinder remained basically the same throughout all years of production, although during the 1990s the reservoir was changed from metal to plastic. Brake master cylinders have undergone a few changes, mainly due to the introduction of dual-circuit systems. The original single-circuit master cylinders were the metal 'baked bean can' type and these, in the main (according to country of manufacture), were fitted into the mid 1970s. Cooper Ss and 1275 GTs had a taller, larger-capacity cylinder. In the mid-1970s dual-circuit brakes were standardised across the UK range and the taller, twin-brake-pipe type of cylinder was fitted. Earlier UK dual-circuit systems were diagonally split but in 1980 they became front/rear split. There are a number of different part numbers for different years and systems so it is necessary to check carefully before ordering replacement parts for your Mini. Not all cylinders are still available. In 1988, until the end of Mini production, a new 'direct-acting' servo brake system was standardised and the position of the brake master cylinder was moved from the bulkhead to atop the servo. This type of master cylinder, the AP Lockheed GMC90376, is much more accessible and easier to change.
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