Hi,

 

Have a problem with the clutch pedal going soft.

I've checked and the master cylinder is dry, and the drip hole in the clutch bell housing is dry.

Also, there is no discernable drop in the clutch/brake fluid reservoir.

The very positive piece of evidence is that bleeding the clutch slave cylinder results in 'bubbles' on the first pump - and the pedal pressure is restored. This sorts the problem for about 500 miles before I need to repeat.

The obvious is to replace the slave cylinder, but as that involves dropping the gearbox, I'd thought I'd call on the collective wisdom of the forum to see if there's anything to try first?

I had a similar problem on an earlier Fiesta and the cause was the slave cylinder.   The car was under guarantee and Fords changed the clutch, then the cylinder but it didn't cure the problem until they changed the slave cylinder.

11 hours ago, Genniker said:

Hi,

 

Have a problem with the clutch pedal going soft.

I've checked and the master cylinder is dry, and the drip hole in the clutch bell housing is dry.

Also, there is no discernable drop in the clutch/brake fluid reservoir.

The very positive piece of evidence is that bleeding the clutch slave cylinder results in 'bubbles' on the first pump - and the pedal pressure is restored. This sorts the problem for about 500 miles before I need to repeat.

The obvious is to replace the slave cylinder, but as that involves dropping the gearbox, I'd thought I'd call on the collective wisdom of the forum to see if there's anything to try first?

Not familiar with the vehicle set up , but if there is no apparent leaking of fluid there must be a way of air seeping into the clutch system. I can only guess it’s on the upward travel of the clutch pedal when no pressure is being applied and air is seeping past the master cylinder seal on the upwards stroke .

The no apparent leaking of fluid confuses me also, so your idea/possibility that it's caused by a suction action is a good suggestion. What might point me more toward the problem being with the slave cylinder is that bleeding the system at the slave cylinder location produces the air bubbles on the first pump, whereas, if it was a the master cylinder at fault it might be safe to assume that the air lock issue would take a while to pump through; especially as the slave is at the lowest point in the system so it would be safe to assume that the air lock hasn't travelled to this point.

 

Given the cumulative millions of miles the fiesta has covered you would think that this isn't the first time that its happened so I guess what I'm looking for is whether others had experienced such a case before and they could share the solution.

 

 

If that's your original slave cylinder, the problem could well be the seal going.

The other factor that I should have added is that it seems that a long journey (heat?) seems to bring on the problem