prestonian

imagination, but wondering if there is something that would cause more pressure required to depress the clutch.
Clutch was replaced 60k miles ago and works fine.
Not sure what the slave cylinder does?
Thoughts?

UrS4boy

In the UrS4 and UrS6, a increasingly "heavy" clutch that needs more and more leg effort to depress is often a sign that the clutch disc is wearing. Very often before the clutch actually slips, the clutch pedal or the clevis pin between the pedal and the clutch master cylinder break due to fatigue cracks. At that point, you are in trouble (some people have been able to start the car in gear and then limp home). Pre-emptive maintenance includes replacing the clutch.

The clutch slave cylinder receives the hydraulic pressure (via a pipe) from the clutch master cylinder and is responsible for moving the pivot arm (clutch release arm) tha is attached to the throw-out (release) bearing which in turn pushes on the release forks on the clutch plate, taking the pressure off the clutch disk, disengaging the engine from the transmission.

Here are some diagrams and part numbers:

Clutch Pedals and Master and Slave cylinders:



The pedal cluster:



The clutch and related parts:



Here is a typical broken clutch pedal:



The problem isn't going to go away take steps to avoid the flatbed.

Paul Heneghan

Additionally, you might crack the pedal bracket - see attached photo. An exceptionally difficult job to R&R on some cars (RHDs anyway) as the steering column has to come out.

UrS4boy

Whoa. Thanks for that photo Paul. Never seen that before. I have stolen your photo to further document clutch pedal-related failures. Not pretty. (I'll give you credit for the photo).

prestonian

I have had the car since 70K miles and replaced the clutch at 110k due to squealing. Car now has 171k miles. I do not drive car hard and have driven many manual cars in my lifetime.
Is there a way a shop can check my pressure plate without just replacing?

scarman

It is certainly not normal, but not unheard of either. My neighbors Sachs pressure plate split in half after 30K miles. It was difficult to diagnose. : )

Paul Meredith at Ringtec Atlanta would be a good choice for a competent, honest repair shop to look at your problem. He comes highly recommended by the Atlanta Audi Club chapter. There are other shops if he is not
convenient- the shop is across Alpharetta Hwy from Nalley Audi (North Atlanta Audi).

I think all the mechanical advantage for clutch operation is in the length of the clutch pedal arm. The hydraulic cylinders are the same size so they just transmit the force. I don't know of any way to visually see the clutch disc and pressure plate without opening things up. Once you spend that money on labor, it makes sense to renew parts.

prestonian

Ringtec is relatively close, so may be worth a trip.
Hopefully my leg is just getting tired in ATL traffic.

UrS4boy

The problem is 60K miles in stop and go computing traffic >>>> 60K of highway miles.

Paul Heneghan

You're welcome Dave.

It was a few years ago now, so my memory may be playing tricks on me, but I seem to remember going through two master cylinders in a couple of months - I think both had snapped rods. When I replace the cylinder for the second time, I could tell something wasn't right - there was clearly something off centre. I have a (unsubstantiated) theory that the bracket cracked due to the very sudden change of force the time the first rod snapped. And then because it was all at an angle, the sideways force on the second master cylinder made its rod snap shortly afterwards, twisting the cracked bracked still further.

Replacing the bracket was a horrible job. The Bentley (which is for LHD models) and the Haynes (which is for non-turbo, non-quattro models) both implied you could remove the pedal bracket without much else coming off. I lay on the footwell for hours unable to see what I was doing, unable to manoeuvre my arms because my elbows weren't double jointed trying to get that wretched bracket out. Eventually I realised that my bracket was a different design to all the brackets shown in the manuals and can only be removed after taking out the steering column.

About a day after I started, I had the steering column out and then the pedal bracket came out really easily. I got it welded for something like £20, and it's been fine ever since - probably done another 30,000 miles since. My wife and I have obviously developed powerful left legs as we are always amazed at the puny little springs fitted to all other clutch pedals!

Still on the original clutch in that car - must be nearly 180,000 miles now.