My car is a former taxi turned private with 210k Km on the clock.

MK3 octavia 5 speed manual, 1.6TDI.

 

When pressing the clutch, there was a low rumble that came and gone but started always when i pressed the clutch. The clutch was acting ok, gears shifted properly and somehow even more smoothly than usual.

2 days ago the clutch pedal suddenly stuck down.

The mechaic replaced both master and slave cylinders and bled the air from the system. I wanted to replace them both in order to prevent a "take me with you" scenario, that the other fails when it's mate is replaced new.

 

Today he bled the air again and i was off to work. 20 minutes later, i got stuck on the highway without any clutch response, no gears were engaged. The clutch pedal went up and down as usual.

The car limped to the garage after i drove it with high revs (the clutch engaged partially), When i got to the garage, The clutch smelled burned.

Now i'm not only replaced the master and slave cylinders, but i'm required to replace the clutch as well.

 

What could be the issue? 

Does the new cylinders caused somehow to the clutch not engaging gears?  Or the cylinders failure were a premature warning to an already worn clutch?

Hi, welcome to the forum. Was the clutch release bearing checked at the time? A noise when pushing-in the clutch suggests a failing release bearing to me.

You have a partial blockage in the clutch bleed block AKA clutch torque limiter which was also the reason that the clutch pedal went half way to the floor, you did not need either of the cylinders replacing although the new master cylinder being an AG revision is worthwhile as it would prevent air being pulled into the system if the clutch pedal is manually pulled back up.

 

The bleed block has no restriction when depressing the clutch pedal (a valve comes off its seat) but has only a tiny microbore for fluid being returned to the master cylinder when the engaging the clutch, the particle will have stopped the return flow causing the clutch slip.

 

Sadly it sounds like another gearbox out job to now replace the clutch, make sure the bleed block and clutch piping is flushed (the fluid will come out black) and preferably that the mechanic drills out the centre of the bleed block to 4.5mm diameter.

Edited 20 April, 20215 yr by J.R.

27 minutes ago, Warrior193 said:

Was the clutch release bearing checked at the time? A noise when pushing-in the clutch suggests a failing release bearing to me.

yes, it was checked during the car buying phase. no noises were detected, gears were changing ok.

 

14 minutes ago, J.R. said:

You have a partial blockage in the clutch bleed block AKA clutch torque limiter which was also the reason that the clutch pedal went half way to the floor, you did not need either of the cylinders replacing although the new master cylinder being an AG revision is worthwhile as it would prevent air being pulled into the system if the clutch pedal is manually pulled back up.

 

The bleed block has no restriction when depressing the clutch pedal (a valve comes off its seat) but has only a tiny microbore for fluid being returned to the master cylinder when the engaging the clutch, the particle will have stopped the return flow causing the clutch slip.

 

Sadly it sounds like another gearbox out job to now replace the clutch, make sure the bleed block and clutch piping is flushed (the fluid will come out black) and preferably that the mechanic drills out the centre of the bleed block to 4.5mm diameter.

 

Hi,

thanks for the reply.

first, I'm not familiar with the details. can you please elaborate regarding the AG revision?

my mechanic ordered a new bursehung cylinders and I don't know if that's related to the revision you are referring to.

second, what particle are you referring to? a rogue particle from dirt in the fluid or the valve?

third, what drilling are you referring to? why is it required in the first place? the is no documentation on this anywhere. can you explain using a picture?

 

thank you very much.

AG revision is the latest VAG part which has the pushrod firmly retained in the piston, pattern parts are likely to be A revision, I have had 2 new A rev pattern part cylinders in the last fortnight where the pushrod came away in my hands.

 

I dont know where the particles come from, probably heat from the DPF degrading the piston seals or maybe the plastic cylinder body, I know they are magnetic because the toroidal magnet at the front of the piston (for the clutch position sensor) had plasticky particles stuck all over it, any one of them was big enough to block the bleed valve return orifice. Also the fluid bled from the clutch was black and full of particles, the braking system I had flushed through with fresh fluid a few months ago but not the clutch.

 

Do your own searching as to why VAG consider that its preferable for the clutch to slip rather than a driver being able to do a quick start off the line (I think its crazy) and you will no doubt find a sectional drawing and explanation of how it works, I am not going to draw one for you even if I were capable of putting it on the computer.

 

There is no documentation because to my knowledge I am possibly the first person to have done the forensic analysis of a failed cylinder and of the pattern part ones and the latest VAG revision and to have worked out why so many people have a clutch pedal not return and get shafted by their garage playing parts bingo with their money.

 

Plenty of people in the racing or tuning fraternity have discovered that the bleed block/torque limiter is a chocolate teapot however rather than sharing that it can be drilled out for no cost they would rather sell you a billet machine aluminium one for a kings ransom.

 

This thread may enlighten you:

 

 

Edited 20 April, 20215 yr by J.R.