86 west water cooled clutch issue


Mpewings

New member
Hello, I'm hoping to get some help with a new issue with my west. The vehicle has 56k miles and has not had an issue however, the past few days I have experienced a soft clutch and at times it will let out while at a stop without pumping the clutch. I notice then when I pump the clutch it works fine for a while but not for long. Nothing has been changed and I know the manual has the brake and clutch system together. No issue with brakes and the fluid is at it's proper level. I'm looking to see if this is a clutch issue or maybe the master cylinder? Thanks for any help you can provide
 

scotsborn

New member
By 'soft' clutch I am assuming that the pedal takes less effort to depress than before. If that is the case then there is probably air in the system.

The system works by using hydraulic fluid (in this case brake fluid) to transfer the motion of your leg / foot on the clutch pedal to the shift fork / clutch assembly between the engine transmission. When you depress the clutch pedal the master cylinder (connected to the pedal) pushes fluid down the tube to the clutch slave cylinder. Thus in turn rotates the clutch release shaft that depresses the diaphragm spring on the clutch cover. This causes the cover plate to release the driven plate stopping the transfer of power from the engine to the transmission.

If the clutch pedal requires less effort to push then the fluid is not being properly moved. Air can be compressed and fluid cannot (for these purposes) so if there is air in the system some of the effort used when the pedal is depressed is presurizing the air and not moving fluid. This results in grinding of gears, hard shifting, stalling and a host of other drivability issues. If the clutch works properly if you 'pump' it then there is probably air in the system. Easy to get the air out but how did it get in there?

The clutch master cylinder is fed from the brake master cylinder reservoir. The brakes are more important than the clutch so the inlet to the clutch is higher than the brake master cylinder so that in the event of a leak in the clutch system you do not loose brake function. What this means is that if the level of the fluid in the brake master cylinder is allowed to get too low then air can enter the clutch system. Once the air is in there the only way to get it out is to bleed the system (Bentley 30.8). Since the level in the brake reservoir gets lower as the brakes wear this level needs to be monitored so that it does not go too low.

So, if the level in the brake reservoir was low and someone topped it up then the cause may be corrected and now the clutch just needs to be bled. If the cause is unknown then you should look for a leak. If there are no leaks then the master cylinder of the slave cylinder would need to be inspected. To determine which one would be defective the clutch pedal should be depressed and the flexible hose near the slave cylinder should be pinched off. Then the pedal can be released. If the clutch release shaft rotates over time (when the flexible line is still pinched off) then the slave is leaking. If the slave is not leaking then the master would be suspect.
 

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