I just bought another Superb 2, this one came with the clutch pedal stuck on the floor, it's possible to pull it up again but as soon as you depress it, it just goes down to the floor with no resistance.

 

I thought it might be the slave cylinder so changed that but I can't bleed it, in fact I can't get any fluid through the slave cylinder at all. I've tried every method of bleeding that there is including trying to suck fluid through the bleed nipple with a Sealey brake bleeder, suction pump and even reverse bleeding by syringing fluid in through the bleed nipple, there is no may of getting fluid out of or in to the bleed nipple.

 

My theory is that the Master Cylinder has jammed in the closed position thereby blocking fluid going in or out of the system.

 

I'm sure someone has had this problem before, so is master cylinder failure or something with the pedal?

You havnt tried every methid, all you need to do is open the bleed valve and let gravity do the rest.

 

The master cylinder is a very simple affair without the multiple seals and non return valves of the past, when it is in the upper position, closed as you incorrectly call it, there is free passage of fluid from the brake master cylinder reservoir through to the slave cylinder, the pistion sits behind the port hence the ability to gravity bleed.

 

What may have happend if you have raised the pedal from the lower position by force is that you have pulled the plastci pushrod out of its retainer in the plastco pisyon and that the piston is stuck in the depressed position blocking off the fluid port, there is no return spring to the piston, its pushed back by the force on the fluid from the cluch diaphragm, there is a control loading spring and cam on the pedal which will push it to the floor in the lower poart of its tarvel and to the top in the upper part.

 

have a feel around with your hand for the pushrod and see if its flapping around.

 

sorry for the typos, cat see what I am yping.

I have tried the gravity method, nothing comes out. there is no way of getting any fluid out of the bleed nipple. When the pedal is in the lower position the master cylinder is closed and it's not possible to get fluid through the master cylinder, hence my statement that the cylinder was closed. So yes, it appears that the piston is stuck in the depressed position blocking the fluid port. 

 

I didn't raise the clutch pedal from the floor, the car came to me like that so I don't know what someone else has done. I've checked the pushrod, is not flapping around it still seems attached to the master cylinder.

 

Why not pop out the master cylinder and take a look at it rather than just guessing? Could also be a blockage in the line if anything got in there.

It doesn't just pop out. The clutch master cylinder isn't that easy to get to so I was hoping for some inspired help from someone who had been there before.  The bottom of the dash needs to come out to get to the pedal, then the pedal complete with Master Cylinder comes out as one unit, but before that you need to remove the 2 pipes connected to the master cylinder and the electrical connector from inside the engine bay behind the engine. 

 

In all my years working on cars I've never come across or even heard of a blockage in a clutch or brake pipe, it's a sealed system, so it would be rather difficult for something to get in there to block the pipe.

 

I've ordered a new master cylinder anyway, they are cheap enough, just a faff to fit.

Update

 

I fitted the replacement master cylinder, not the most pleasant job as you need to remove the knee airbag and part of the dash, then access to the Master Cylinder from inside the engine bay is very poor so you scratch your forearm up.

 

Once fitted I could get fluid to bleed through the system and managed to get a working clutch pedal. The pedal is still a bit low because there's still some air in the system. The local garage are MOT'ing the car tomorrow and will bleed the clutch again (there's a knack to it)  while I wait.

 

Diagnosis was faulty master cylinder.

It will self bleed now.

 

Been there & got the T shirt re fitting master cylinders, with the clutch pedal and the outlet pipe removed (easier said than done) not forgetting the inlet pipe and switch connector the master cylinder can be removed with a twist of 1/4 turn.

If you want to pull the old one apart to see what has happened on the inside I can let you into the secret of how to disassemble the clipped together assembly that is designed to never come apart.

 

Mine had a huge amount of magnetic sludge like debris sticking to the toroid magnet on the end of the piston, I have no idea where it came from, the seals were intact, I initially thought the magnet was there like an engine oil magnetic drain plug, to catch metallic debris but of course there should never be any, the magnet is to operate a reed switch for the clutch position sensor.

 

Which begs the question where did all the magnetic Schmoo in mine come from and does your cylinder have it also?

 

When you get fed up trying to release the sprung lugs joining the two sections I will let you into the secret!

On 23/04/2023 at 21:43, J.R. said:

It will self bleed now.

Took it for the MOT yesterday, on the drive there the clutch pedal was almost on the floor. I warned the tester of the issue with the clutch pedal but when he jumped in the pedal was just about perfect and has remained that way since.

 

So problem solved.

Dont kid yourself, I too have been there, you have not even found the actual problem yet, you have like me been wisely replacing the easy and obvious bits, I dont doubt that your master cylinder benefitted from replacement, mine was full of metallic schmoo, but as you have seen the problem has recurred and will soon become an all too frequent occurrence.

 

At the end I was having to stop and bleed the clutch (very quick, easy & no tools needed) twice in a 5km urban journey, it was really a gamble doing a long journey, once on an autoroute the clutch was not used but you never knew when coming off at an exit or péage whether it would disengage, every time I would have to look for an escape route, a verge or whatever I could steer to to bleed the system again.

 

I hope you dont have any long journeys coming up soon.

 

My use of "self bleed" does not mean that any air will rise up through the system and exit through the fluid reservoir although air in the upper pipe may well do so, it meant that you dont need pressure bleeders or anything, when you release the bleed thumbturn on the slave cylinder or clutch bleed block gravity alone will purge out the air gathered there in the chamber designed for it to gather, its a high point and the air cannot travel down to then travel back up through the rest of the system, it remains there.

Let’s see what happens over the next few weeks?

There’s not much else in the hydraulic system to fail.

You will indeed, when the weather turns warm will be a key milestone.

3 weeks down the line and I've had no symptoms of air in the hydraulic system.

However the slave cylinder let go today which is probably down to the clutch being rather heavy, probably due to an issue with the cover plate. 

I'm too old and rancid to do the clutch myself so getting the guys at the local trusted garage to do it, they say they have seen a stiff clutch have this affect before.

An update in 2 weeks when the clutch is done and I'm back from the training course I'm going on.

Update.

I replaced the complete clutch about 4 weeks ago and installed another new slave cylinder. So far so good, no more issues with air in the system, no fluid leaks and the clutch itself is much lighter.

I hadn’t realised how heavy the old clutch was but this was probably the original fault, the heavy clutch put additional strain on the hydraulic system and the plastic slave cylinder was drawing in air before it finally let go.