The clutch hydraulic system is the mechanism that transmits the driver’s pedal effort to the clutch release mechanism. It consists of a master cylinder in the pedal box, a hydraulic pipe running from the master cylinder to the slave cylinder on the gearbox bell housing, and on the 1275cc, a flexible hose section between the rigid pipe and the slave cylinder that accommodates engine movement on its mountings.
Drivetrain
The Midget clutch hydraulic system is notorious for being difficult to bleed. The geometry of the pipework creates air pockets that conventional pedal-pumping bleeding struggles to dislodge. A pressure or vacuum bleeding tool is strongly recommended, it provides a continuous flow of fluid through the system that pushes air bubbles out far more effectively than intermittent pedal pressure. Even with a pressure bleeder, the process may need several cycles before the pedal firms up completely.
Clutch Cylinder Seals and Hoses
The master cylinder and slave cylinder seals deteriorate over time, particularly if the car is stored for extended periods without the clutch being operated. A hydraulic system that has sat idle for several years will almost certainly need both cylinders rebuilt or replaced. The 1275cc flexible hose is an often-overlooked failure point, an ageing rubber hose can expand under hydraulic pressure rather than transmitting the force, causing a spongy pedal and poor disengagement even with new master and slave cylinders. A stainless steel braided clutch hose eliminates this issue entirely and is a worthwhile upgrade.
1500 Clutch Hydraulic Pipe
The clutch hydraulic pipe on the 1500 differs between non-dual-circuit brake cars (3/16" bore) and dual-circuit brake cars (1/4" bore). The chassis number determines which specification is correct.