4kq, slipping clutch :(

[E. Roy Wendell IV]

snip
> ... that said, it does indeed seem odd that the clutch only slips in 
> 4th
> gear ...

Not really, and I imagine that it slips even worse in 5th gear. The 
higher the gear the less mechanical advantage in the provided by the 
transmission and therefore a higher torque load on the clutch. Slipping 
clutches always show up at full throttle in high gear first. Running in 
a lower gear and higher rpm provides the same torque at the wheel but 
much less at the flywheel which is how you can get a car with a worn 
clutch to limp along for a while. Top speed of course is limited.

> ... the failure of the pedal to return to the full up position is not 
> likely
> to be related.  I'd imagine that you're getting a bit of leakage past 
> the
> internal seal in the master cylinder ... I've found that bleeding the 
> clutch
> can restore function, but it may require a clutch M/C swap.

Yup, hydraulic problem it is. The "return" spring on the pedal assembly 
isn't, actually it pushes the pedal down. The return force is provided 
by the clutch pressure plate diaphragm spring via the throw out 
bearing, clutch force, slave cylinder, fluid, and master cylinder. When 
the hydraulic system no longer seals and keeps a direct relationship 
between pedal position and throw out bearing position then the pedal 
starts getting lower and lower and/or magically sinks down to the floor 
by itself. Temporarily you can limp along by hooking the clutch pedal 
with your toe and lifting it back up. Don't sit at a traffic light or 
anywhere else for that matter with the car in gear and the clutch 
depressed. When the clutch hydraulics get really bad the clutch can 
engage no matter what you are doing with the pedal. The clutch itself 
is spring loaded to the engage position. Once you loose the ability to 
transmit a force to it via the pedal to counteract the pressure plate 
spring it will engage and your only resource is quick action with the 
brake and key.

> Since we're talking about a car that is approaching its 20th birthday, 
> and
> which very likely still sports the same clutch components it had when 
> it
> rolled off the production line ... if you do decide to do the clutch 
> you may
> want to consider replacing (or rebuilding) the master and slave 
> cylinders
> and replacing the flexible line in the clutch circuit ...

Ditto. Good luck with rebuilding the clutch hydraulics. The kit is 
difficult to find and both the master and slave cylinder bores are 
likely rusted beyond the point where a hone will restore a smooth bore. 
No one ever bleeds these systems and the fluid in the clutch slave has 
likely been there since 87 and is about 50% water. Rust pitting of the 
cylinder bore is the usual source of failure since the rough surface 
cuts and abrades the chevron seal on the piston. Then the fluid 
bypasses the piston and therefore develops no force.

Roy Wendell
Morgantown WV, USA
turbo quattro type 44 times 3