Clutch Bleeding: No brake fluid flowing, possible master cylinder ?

[tornadored7]

Background:

Car: Golf GT TDI PD 130
Gearbox: 02M.ERF

Car was suffering from the common 02M problem of a non returning clutch pedal, (i.e. a very low biting point, and also after pressing down the clutch pedal it would only return up halfway).
This was always worse when the car was cold, and became less severe after the car was driven for 10/20 minutes.

I struggled with the car like this for a few weeks, but more recently things worsened as gear changes began to become very difficult when first starting the car.

Knowing that the brake fluid in the Clutch/Concentric Slave Cylinder (CSC) is never flushed during a brake fluid change, I planned to suck the old brake fluid from the CSC and follow this with a clutch bleed.

I removed the plastic T piece coupled to the CSC, connected a hand vacuum pump and tried to suck out the old brake fluid. Despite several attempts, only a minimal amount of brake fluid was collected.


Problem:

The real problem then came when reconnecting the T piece to the CSC, then trying to bleed the clutch.
Using a Gunson’s Eezibleed pressurised to 29 psi (2 bar), absolutely no brake fluid emerges when the CSC bleed nipple is opened

Instead of brake fluid trickling from the CSC nipple, it overflows from the brake fluid reservoir, almost suggesting a blockage somewhere in the clutch hydraulics ?



Symptoms:

· Despite using 29 psi of pressure, also manually by cycling the clutch up and down or when applying 20 in hg of vacuum using a vacuum pump, no brake fluid is flowing from the clutch bleed nipple.

· No signs of any brake fluid leakage anywhere (near the clutch pedals, the clutch pipework, the diaphragm valve, the brake fluid reservoir, the clutch flexihose, the T piece, ...)

·Brake fluid level in resevoir remains constant, regardless of whether pedal is pressed or not

· There is clearly air in the hydraulic system, since the clutch pedal drops to the floor and must be manually returned to an up position.

· The ‘blockage’ is at a point before the diaphragm valve, since the pipework after this (including the clutch flexihose) flows brake fluid.
Checked by disconnecting the diaphram valve (round box near the ABS pump), and pushing in a spare CSC that was connected up.

· With a vacuum pump/gauge attached to the pipe where the diaphragm valve normally connects, the vacuum level rises when the clutch pedal is brought up. There is a corresponding decrease in vacuum when the clutch pedal is pushed down

· Likewise, airflow can be heard when lifting/dropping the clutch pedal.



What next ?

1) Does this sound like a fault with the clutch master cylinder (CMC), and what are the definitive symptoms for a worn/faulty CMC (including seals being damaged/having flipped over) ?

2) Is there any way to diagnose CMC issues, either with the CMC in situ or by disconnecting pipes ?

3) Is it worth disconnecting, then reconnecting the CMC to check whether this has any effect ?

4) I have a spare CSC that could be used, if this aids in diagnostics

5) Is it worth getting underneath the car to have a look round, and what/where should I be looking/for ?

6) Any other suggestions please ?

[Crasher]

Sounds like a faulty release bearing, change the MC first and if that does not work, pull the box out.

[tornadored7]

Thanks for the reply Steve.

I'll try the CMC first, however am a little confused since (without having a more thorough examination) there doesn't appear to be any brake fluid leakage from the CMC.

I'm trying to better understand the problem.
Why would a faulty CMC prevent/block the flow of brake fluid, since the behaviour appears exactly like a blocked clutch hydraulic line ?
In the first instance, as mentioned, with the clutch hydraulic's diaphram valve (DV) removed, there is no brake fluid flow from the CMC, suggesting a problem before the DV (i.e. the from the CMC), but I can't see why.

On a more worrying note; given the mileage, replacing the CSC would also warrant;

• Clutch replacement
• DMF replacement
• A gearbox strip down to replace the 1/2 gear 02M selector fork engager rivet with an M6 10.9 grade bolt/nuts

I've done this previously on the floor with the car on axle stands, and it really isn't much fun .

Regards,
TR7

[Crasher]

They don’t leak out when they fail.

[tornadored7]

They don’t leak out when they fail.

Thanks for clearing that up Steve.

Do you know whether the GSF sourced FTE master cylinder, is as reliable (ideally more so) as the original Sachs manufactured one ?

Regards,
TR7

[Crasher]

We only fit genuine VAG dealer sourced concentric slave cylinders. For the few pounds more that they cost the 2 year parts and labour warranty is worth it, if the thing should fail within two years, let them change the bloody thing!

[Will T]

Hi,

I had this non-returning clutch pedal problem on our '52 Golf Estate 130PDI. I found that if the pedal was pulled back manually it would be fine for a while then do it again. Anyway, I had a local VW specialist look at it and they said it was a problem they'd seen before on Golfs, and that it was to do with a lever system designed to make it easier to hold the clutch pedal down (some sort of cantilever arrangement?). After finding nothing wrong with any of the system components (plus the car had had a major service several months before at a VW main dealer and nothing was reported amiss in this area) they applied a known fix that involves cutting away some plastic trim somewhere, I believe, in the footwell. They said the trim can sometimes get in the way of the pedal/lever assembly. Since then, no re-occurrence! (touch wood). As for the trim surgery, when I got the car back I had a look as best I could deep in the footwell and couldn't see anything cut or missing, so I can't help you with any details (although the garage might...)

Will