Clutch Master Cly keeps failing?

[jprine]

I'm at about 300k, on this 6speed and clutch since about 160k (new VW slave cly/throwout bearing when installed).
Was quite a while (50k+) after I did the 6sp and new slave that I had my original clutch master finally fail - eventually wouldn't disengage the clutch.

New clutch master instantly fixed it - but didn't last more then 6 months or so.
Figured it had a defect, swapped a 2nd replacement - this one failed even quicker and left me stranded and needing a tow home.

While doing third replacement I decided to completely clean the brake res as I noticed some floating oily metallic stuff floating on top - seemed to be coming from the low fluid float switch/cap. Looks like the metal spring in it is disintegrating somehow? I sucked all the fluid out and yanked the plastic res body off the brake master. Cleaned the hell out of it as well as the cap and put it back together and finished the job.


Held up for about 8 months before the pedal started engaging lower for the past couple weeks and now I can't fully disengage the clutch again.


I noticed this time as it was starting to fail the last couple weeks - sometimes it would randomly disengage higher up a few times and then back to lower again. Very similar to this post which also happens to be a 6speed in a mkiv: https://forums.tdiclub.com/index.php?threads/help-clutch-went-to-floor-wont-disengage.171072/page-2 - But no clear answer, (going to double check to make sure my 'bleed T' is clipped in securely).

Not loosing fluid and when I hold the clutch down for a while it doesn't loose pressure so I'm sure its the master again and not the slave. Sure it will be instantly fixed again after clutch master replacement but I am sick of this.. what is the long-term fix? Do I need to modify one of these masters with better o-rings or something?

edit: One change, some of the previous failures the pedal would get stuck down - currently with this one it still comes at least most of the way back up and still half functions, just not enough to fully disengage the clutch. Also seems like this last one never engaged as high as original one did but that is really hard to compare and say for sure.

 

[Seatman]

Is the clutch pedal and everything ok? I can only think something is bent and pushing the plunger wrong or the fluid is contaminated and ruining the seals?

I had one fail once then never again, it was a friends car that I then bought and sold to another friend but none of us ever had it fail again but we got some mk4 with 6spd as standard. Maybe some other difference in the layout. Only reason the first failed was the previous owner had done a bit of botching.

 

[jprine]

Just replaced it and its working great again and engages where it should. Was thinking the contaminated fluid thing before, why I emptied and cleaned the res but a tiny bit was in the brake master that came back when I refilled. The brake master cyl is original to the car 300k miles and shares the same fluid, so it doesn't seem to make sense that it would harm the seals so bad/fast. Thinking just cheap parts. This new one is metal, crossing my fingers.

Some notes:
Checked the bleed-T before and it was good (original clips and secure)
Tried to gravity bleed - does not. nothing comes out.
Tried to pressure bleed with pedal pressed - a bit ejected and master would not build anymore.
New master - gravity bled fine, builds pressure etc.

 

[BobnOH]

How often do you do a complete fluid replace on the brake hydraulic system?

 

[jprine]

How often do you do a complete fluid replace on the brake hydraulic system?

Did 100% flush/change when I did the transmission at ~160k (purchased car at 100k). First clutch master failure was after 200k.
Probably twice more since when doing brake pads. Pulled the res off the brake master and cleaned back to transparent during 3rd clutch master replacement..