Clutch hydraulic line leak at slave

ymz

Top Post Dawg
Joined
May 12, 2003
Location
Between Toronto & Montreal
TDI
2003 Jetta TDI Wagon, 2003 Jetta TDI Wagon
2003 Jetta... lost the clutch, so I bled the system and noticed that it had been leaking where the line joins the slave cylinder. So I replaced the "O" ring (from the kit numbered 1K0 721 741... (I know it's now been superceded by 1K0 798 741). Still leaks... now these kits come with 2 "O" rings and 2 cup-shaped seals, but whenever I look at a diagram, only the "O" rings are shown... is there also a seal (the cup-shaped one) inside the slave cylinder?
 
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Keystoner16

Veteran Member
Joined
Sep 23, 2019
Location
Eugene, OR
TDI
2011 Golf TDI 2.0 CR, 2004 Golf TDI 1.9 PD
The factory manual shows a single o-ring at both the master and slave ends of the the hydraulic clutch line.
Not sure what the cup seals would be for.
The factory manual states that the o-rings should be "moistened" with brake fluid before install.
If you did not clean both the line and slave cylinder well, it's possible dirt has compromised your seal. Or, the o-ring was damaged due to lack of lube before install. Also, the clip could be distorted in some way, although that might be unlikely.
If you have ruled all of the above out, I would just go ahead and replace the slave cylinder.
 

ymz

Top Post Dawg
Joined
May 12, 2003
Location
Between Toronto & Montreal
TDI
2003 Jetta TDI Wagon, 2003 Jetta TDI Wagon
I'll try to "borrow" a slave and a hydraulic line from my parts car - if I can figure out a way to get at the attachment to the master cylinder... it looks very tight in there...
 

Nuje

Top Post Dawg
Joined
Feb 11, 2005
Location
Island near Vancouver
TDI
2002 Golf 6MT; 2015 Sportwagen 6MT; 2016 A3 e-tron 6DSG
I've discovered that there are two types of ends to the clutch line - one has a flared end to it (plastic or metal) (that one uses only the O-ring):


The other one, which has maybe 2-3mm of steel hydraulic line protruding past the end of the plastic cowling (or whatever it might be called). That cup-shaped rubber bit fits over the end of exposed metal line.


That cup-shaped rubber piece sometimes gets wedged / stuck inside the hydraulic cylinder. Might be worth confirming that nothin is wedged in there (as fun (not) as it is to get up/under/in that master cylinder outlet).
 
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ymz

Top Post Dawg
Joined
May 12, 2003
Location
Between Toronto & Montreal
TDI
2003 Jetta TDI Wagon, 2003 Jetta TDI Wagon
OK... I give up... how does one get at the other end of the Clutch Hose (at the Master Cylinder) ?? I would hope you don't have to unbolt the ABS pump... I've been searching for a guide online, but none of them show you how to gain access...
 

Nuje

Top Post Dawg
Joined
Feb 11, 2005
Location
Island near Vancouver
TDI
2002 Golf 6MT; 2015 Sportwagen 6MT; 2016 A3 e-tron 6DSG
If you pull the wiring harness off of the ABS pump (slide lock pulls up, IIRC), you get slightly better access to it. "Slightly" being the operative word there - it's still a royal PITA no matter how much you pull away.

Then there's a little wire U-clip you have to pull out, then yank the steel hydraulic line straight down. Have the steel line released from all of the clips holding it in place, too, otherwise you'll end up trying to bend steel as your pulling it out.
 

Nuje

Top Post Dawg
Joined
Feb 11, 2005
Location
Island near Vancouver
TDI
2002 Golf 6MT; 2015 Sportwagen 6MT; 2016 A3 e-tron 6DSG
Here's a thread from Vortex that outlines the basic steps of the whole master cylinder replacement - so a person could extract from that the relevant part of simply (🤣) removing the hydraulic line from the MC.

I think the reason you won't find videos is that even without a camera, you're pretty much working blind - feeling around for everything you need to do, with your hands and car parts totally blocking what you're working on.
 
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ymz

Top Post Dawg
Joined
May 12, 2003
Location
Between Toronto & Montreal
TDI
2003 Jetta TDI Wagon, 2003 Jetta TDI Wagon
As was stated.. it's a pain, but it's do-able... BTW - contrary to some of the postings out there, the little clip that holds the line to the master cylinder IS removable on my cars, so... care must be used... (an extra-long set of long-nose pliers is helpful...)

PS: the part number for the little clip is 7M0 721 431... The part number for the "O" ring is 02F 141 143A (9.25x6.07x1.78mm) The Canadian parts supplier RoselandTech supplied me with spares that, fortunately, I didn't need this time around...

Y.
 

Nuje

Top Post Dawg
Joined
Feb 11, 2005
Location
Island near Vancouver
TDI
2002 Golf 6MT; 2015 Sportwagen 6MT; 2016 A3 e-tron 6DSG
the little clip that holds the line to the master cylinder IS removable on my cars
Anything is removable if the tool is big enough. :D

Seriously, though, glad to hear you got it all apart and back together and working.
 

Yorkie123

Member
Joined
Oct 14, 2024
Location
United Kingdom
TDI
1.4 TDI BNV
I’m having the same issue, new o ring and cup seal and it’s leaking, I’ve swapped slave cylinder from another parts gearbox and it’s still leaking..

At one point it held a seal out of the car (Clutch line installed into slave cylinder but slave cylinder not installed to the car) but then when installed on to the gearbox and starting to bleed the system of air, it began to leak again.

I have tried to 2 slave cylinders, new seals and it just won’t hold pressure. Some ideas would be greatly appreciated.
 

pkhoury

That guy with the goats
Joined
Nov 30, 2010
Location
Medina, TX
TDI
2013 JSW, 2 x 2002 Golf, 1995 F450 7.3L
Good thread - this happened to me yesterday afternoon, and it's amazing when you can't move from a turn lane, how many people don't know what hazard lights means, even after you've been stationary for over 5 minutes. Even more amazing that people don't know what it means when a police car is behind you with lights on.

Got home and sure enough, it was dripping a bit of fluid from the hard line that attaches to the slave cylinder. I put in both a new line and new clutch pedal from my former Ute project. The replacement line was the plastic type and still somewhat leaky, but the old line seemed to work with the different clutch pedal. My brakefluid was kind dark, after about two years since changing it, so that all got flushed out and I did a 5 point bleed with a harbor freight bleeder kit. Brakes and clutch pedal feel pretty tight now. It's tempting to pull the line to change those bushings at some point in the future, but I also don't want to have to do this job over again, either.
 
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