Clutch biting on it's own

[Ads1987]

Hi Guys,

Continuing the ever lasting list of repairs!

Our van has gradually been developing a clutch issue, started with 4th gear being a bit tricky to release, I found if you pumped the clutch pedal it would eventually work. This then developed into it being harder to select first unless the pedal was pumped, same as reverse.

Anyway I checked the fluid level and it was ok, so then checked the salve cylinder boot and it was full of brake fluid, ah hah! I thought. Had great fun trying to get the pipework undone and in the end replaced the slave pipe section and flexi, rebled it all and retried.

However still had an issue with it grabbing the gear, I adjusted the freeplay of the pedal at the master cylinder as I thought maybe the bite point was just a little low.

After attempting another bleed, I noticed the release lever actuates like you'd expect when you depress the clutch pedal but it lifts back up on it's own. So essentially when you push the clutch pedal down and hold it down, it engages the drive again on it's own and doesn't hold pressure. The fluid level is staying the same, no obvious leaks and it bled through the new slave without bubbles as you'd expect. 

I'm guessing the master cylinder has failed and is now causing the issue, it's not leaking fluid but I guess this should maintain the pressure?

Just thought i'd check to see if anyone has had a similar issue or opinions on the best course of action?

Thanks for reading !

Adam.

[Mr Bean]

As far as I can work out from your description you are on the right track. Not sure whether the fluid volume per foot pedal travel is sufficient but if you peer into the reservoir (possibly using a mirror or helper) as you push the clutch pedal to the floor, you may see the initial dip in level and see it come up again as the clutch pushes the slave cylinder back under the force from the clutch diaphragm spring. Surely in the absence of a visible leak or a need to top up periodically, the only place for the fluid to be going is back intro the reservoir. 

Let us know how you get on.
 

[Mocki]

Yep going by your description alone I would say master has failed , or is failing . 
I would also be sure to change the fluid completely because if the master has failed , it will have contamination 

[Ads1987]

Yeah I spose the slave will ultimately work both ways and the master is the one that needs to maintain the pressure to keep the slave pushing the clutch release lever down.
Think I'll just order the master, at least it's easier to change! (fingers crossed lol)

Cheers guys,

[Mocki]

Easier to change as long as you have thin fingers .....

make sure you keep the little plastic Ferrell from the old one , as far as I know the new ones don’t come with them 

[Ads1987]

Yeah I got to it earlier when I adjusted the pedal freeplay and that's most of the job apart from undoing the fluid lines so will hopefully be OK as these aren't on the outside getting rusty!
Not sure what ferrel you mean but I'm sure it will make sense when I get the old one off, won't throw anything away

[Mocki]

Where the pipes join on .... you will see 

[Ads1987]

All done, the new master came with the white bit too
Works nicely now so it was the master cylinder not holding the pressure down.

Thanks for the help guys