Discussion
A friend has MGBGT which has a soft clutch pedal. The seals in both master and slave have been replaced but it's still soft. I've read the system is a swine to bleed. We've tried Eezibleed & manual method but still no joy.
Clamping the flexi just before the slave stiffens the pedal so the master seems OK. What I did notice is that manually pushing the slave cylinder piston in gave a better feel temporarily. Does the system rely on the clutch lever arm to push this cylinder back in or does it rely on an internal spring ? If you disconnect the clutch arm from the slave you can move the clutch backwards & forwards but there is absolutely no 'spring' back. Is this normal ?
Appreciate any help
Clamping the flexi just before the slave stiffens the pedal so the master seems OK. What I did notice is that manually pushing the slave cylinder piston in gave a better feel temporarily. Does the system rely on the clutch lever arm to push this cylinder back in or does it rely on an internal spring ? If you disconnect the clutch arm from the slave you can move the clutch backwards & forwards but there is absolutely no 'spring' back. Is this normal ?
Appreciate any help
This is a common'ish problem with MGB clutch cylinder bleeding but there's a good trick that works every time with use of a re-usable cable tie.
1. Start as if bleeding for the first time - fill master cylinder and fit cap.
2. Push slave cylinder piston fully back and hold in position with re-usable cable tie; then bleed.
3. Close bleed nipple, release cable tie, and top up master cylinder. Here be sure not to let fluid level drop too low.
4. Again push slave cylinder fully in and hold in position with re-usable cable tie; then bleed.
5. Repeat points 2-4 until firm clutch is felt - remembering to fit MC resevoir cap each time!
6. As effective bleeding/top up continues you'll notice greater resistance when pushing back SC piston.
Some guys use wire but you'll find the re-usable cable tie much easier. I normally raise car onto 4no axle stands, this way I can check clutch/through all gears with engine off, and then, with engine on at tick-over. This way you'll know you have a smooth gearchange/clutch bite without having to test drive each time. Once all okay take for good test drive.
Note: where the MC & SC seals have been replaced the cylinder bores need to be in perfect condition or you'll loose effectiveness. Also, the MC replacement seals have a tendency of poor fit or roll back if not installed using fluid as lubricant at point of fitting. Good luck.
1. Start as if bleeding for the first time - fill master cylinder and fit cap.
2. Push slave cylinder piston fully back and hold in position with re-usable cable tie; then bleed.
3. Close bleed nipple, release cable tie, and top up master cylinder. Here be sure not to let fluid level drop too low.
4. Again push slave cylinder fully in and hold in position with re-usable cable tie; then bleed.
5. Repeat points 2-4 until firm clutch is felt - remembering to fit MC resevoir cap each time!
6. As effective bleeding/top up continues you'll notice greater resistance when pushing back SC piston.
Some guys use wire but you'll find the re-usable cable tie much easier. I normally raise car onto 4no axle stands, this way I can check clutch/through all gears with engine off, and then, with engine on at tick-over. This way you'll know you have a smooth gearchange/clutch bite without having to test drive each time. Once all okay take for good test drive.
Note: where the MC & SC seals have been replaced the cylinder bores need to be in perfect condition or you'll loose effectiveness. Also, the MC replacement seals have a tendency of poor fit or roll back if not installed using fluid as lubricant at point of fitting. Good luck.
gifdy said:
Thanks - we'll give that a go. Can you answer the question on the return ? Is is the internal springs or clutch which returns the slave piston ? It would help understand how it all works.
Both. The return spring at top of the clutch pedal arm returns the clutch pedal and MC piston to their 'static' positions. The MC piston is under mechanical [levered/fulcrum] pressure when clutch pedal is pressed, this in turn pushes the sealed system hydraulic fluid into the SC which forces SC piston to move the armatures on clutch pressure plate to 'open' the clutch via the clutch arm and throw out/thrust bearing :. enabling change of gear. The hydraulic pressure [movement] needed for this is not huge. The SC piston and pressure plate armature returns to its normal 'sprung' position i.e. clutch under drive/friction position when the clutch pedal is released. Gassing Station | Classic Cars and Yesterday's Heroes | Top of Page | What's New | My Stuff