We've been having various problems lately with jerkiness taking off from a standstill.  I thought it was all about engine unevenness but I'm starting to change my mind, maybe.

An observation last weekend, when comparing the Fabia to both Polos, was that the engage/disengage point of the clutch is a looong way further down the pedal travel on the Fabia, like in the last two or three centimetres before the pedal hits the stop.

 

Another, that I've just noticed this morning,  is that the first few cm of pedal travel meets almost no resistance at all. There's much less 'no resistance movement' on my comparison cars.

 

Here's a little video I just made of me pushing it down with my little finger.

 

 

I just had the slave cylinder off briefly to check for fluid leakage, of which there was none.  The slave is recent, dating back only to the clutch change that wasn't very many years ago.

 

Last weekend I bled the clutch, and although the fluid that emerged was nasty and dark, there were no air bubbles whatsoever.

 

Is this looking like a master cylinder problem?

 

Saw on youtube a vid where the guy clamped the flexi part of the hose between master and slave, looking for a rock-hard pedal as a result. Didn't get it so concluded fluid leakage at the master.  I'm slightly reluctant to try this as I don't have a proper hose clamp tool, and that bit of hose is 15 years old.

 

Your thoughts please people.

 

 

 

 

 

 

Hmmmm, mine moves about the same amount with the little finger but the biting point is a lot higher.

Thanks for checking Lee, it's a bit of a mystery to me. I may have to get brave and clamp that hose to see what happens with slave cylinder and clutch mechanics isolated from the action.

 

Just to clarify the description of this test in the opening post; the leakage mentioned was reckoned to be past the seal(s?) of the clutch master cylinder, so spoiling it's efficiency, not an external leak.

Edited 18 July, 20205 yr by Wino

I would have thought you would need just a little movement so as not to have the clutch on the edge of disengaging... 

A half way decent clamp is fairly cheap and easy to source and usually made of plastic so I would think it would not damage the hose more then the internal pressure would, if you see what I mean. I am sure you don't drive with your foot slightly resting on the clutch lever as many inexperienced drivers do. This is a guaranteed clutch killer.

I don't think I really understand your first sentence.

 

It's not a car I drive much so don't really know what happens to the pedal, but the original factory clutch kept going from when we acquired the car at roughly 100k, 8 years ago, until about 145k (3.5? years ago) with the current owner/driver so I doubt she does much wrong.

 

I found a new replacement master cylinder on ebay for barely more than £20, so I think I'll just swap that in and see if anything improves.

1 hour ago, Wino said:

I don't think I really understand your first sentence.

 

 

 

I think he means there needs to be a little bit of free travel at the top of the pedal so that the clutch isn't being held under pressure.

Experiment tried today.

Pumping the clutch pedal a few times before attempting to select first/reverse seems to improve the situation to normal behaviour. I've got a good feeling about this master cylinder idea. 

^ That was the experiment as conducted by the owner.

I borrowed the car today and had no such luck improving anything by pumping the pedal. 

Replacement master is on the way, so will get fitted anyway, but not as confident as I was yesterday.

There's not much to it really. If you've already renewed the slave it can't be much else, unless there's something wrong with the actual clutch. Hope not though.

Thanks, friend. 

Well it wasn't the master cylinder. 🙄

Have literally just had another idea that might be easyish to check once the rain stops - could it be that the flexi section of the hydraulic hose between master and slave is swelling/ballooning somewhere, taking some of the fluid that ought to be pushing the slave cylinder's actuator?

Far-fetched and probably just me being in denial about there being something wrong inside the bell housing. Fingers crossed though...

Deffo worth checking.

Had a go a few minutes back.  Nothing bulgy but interestingly, the whole flexi section can be felt to move slightly (in the direction of the arrow) as the clutch pedal is pushed fully to the floor. Not sure if this is to be expected, or how to imagine exactly what's going on structurally there; but doing the same check on my Polo results in much less noticeable (but still detectable) motion in the same direction.

 

 

The hose is trying to straighten under pressure, it's normal.

Thanks, that sounds reasonable.

Starting to think I must've knobbed up something when I swapped gearboxes 16 months back. I bought a JJL code gearbox on instead of the original GSB code, without much research or thought, beyond knowing that they were fitted to the 1.2/12v engines a little later.

 

Tempted to try cobbling together a short extension piece to go on the end of the slave cylinder actuator to see if that moves the biting point away from the floor.

Just a thought, did you replace the fork when you did the clutch? When I had mine done recently it came with a new fork because the originals bend over the lifetime of the clutch.

Struggling to remember. Certainly considered it, and have a vague memory of finding that local GSF had one on the shelf. Email/purchase records should be able to remind me. 

Looks like I did, Sachs part from GSF via ebay; and judging from some photos I was looking at earlier of the 'new' gearbox minus a fork, I swapped the recent one over onto it.

Can't see any harm in an experiment to extend the slave actuator so I'll have a look at adding a few mm to that somehow. Think I've still got the slave that came with the JJL box too somewhere, maybe.

Edited 25 July, 20205 yr by Wino

I might be wrong but when i think of it, if you add few mm below the slave cylinder, the piston will protrude little more from the housing until it touches the fork, but the piston travel should not change when pushing the pedal. You could get shorter maximum piston travel so that the clutch doesn't disengage when pedal pushed in.

Not sure about that. 

The problem right now is that at maximum pedal travel downwards (= maximum slave cylinder piston extension) the clutch only just disengages. So lengthening the actuator attached to the piston should make the clutch disengage with less pedal movement, no?

Sorry about that, i imagined you would insert a washer below the body of the slave cylinder. Yes, lenghtening the actuator should bring the biting point to a higher position.

If it is easy, check if for different gearboxes there are different lenght slave cylinders.

No need to apologise, made me double-check my thinking. Never a bad thing.

@Wino My 2007 Mk1 Fabia with the 02T HZK gearbox behaves in a similar way. I'd like a firmer pedal and if that doesn't take stripping half the engine bay it would be nice. Keeping an eye on your fixes if there are any.

 

 

Interesting twist to this tale just now.

 

I bought a (recent) secondhand  slave cylinder of the part number superseding the one I bought at the time of the clutch replacement, with a view to maybe modding it as a workaround solution to the clutch engagement/disengagement point  being so low on the pedal.

So the one currently connected to hydraulics (dustier one on the right) is a genuine 6QE721261; the one that turned up yesterday for me to have a play with possibly extending is 5Q0721261.

Looking at the latter after its arrival yesterday, I had a nagging suspicion that the plunger/actuator seemed a shade longer at max extension than what I saw in the car last weekend, so here's them side by side:

 

There's a good 5 or 6mm difference there, which is ballpark what I was thinking of trying as a modification.  

So maybe I just need to fit this other slave cylinder.

Stand by for the next installment over the weekend...😀

 

Edited 31 July, 20205 yr by Wino

Strange how the lengths are different. Looks promising though 👍