Confused by gearbox problem

[Bertie]

I've got a 1994 993 Carrera with a gearbox problem that's confusing me. Without doubt it'll be going to my local dealer to get sorted, but it'd be nice to understand what the problem might be.

From cold, the car won't engage reverse or first gear (clutch fully depressed and with any amount of brute force). With the engine off any gear can be selected smoothly. First gear can sometimes be obtained by getting going from second to first, although second is increasingly hard to get. Once in reverse or first, it can be difficult to disengage them.

After two miles of driving, the gearbox is as smooth as silk and every gear can be obtained. Even after a two mile journey, the gearbox remains smooth even if left for 12 hours.

I've got a reasonable understanding of the clutch and gearbox (not enough to consider doing the work myself though), but I can't come up with a theory that explains what's going on.

Any thoughts much appreciated!

Bertie

[bazar01]

Hi Bertie, your problem looks like the clutch is not disengaging fully with engine running, so the difficulty in shifting. The difficulty in shifting out of gear is also an indication the clutch is not fully disengaging. I will not drive the car in this condition because it can do some damage on the more expensive transmission.
Clutch not fully disengaging can be due to a number of reasons.
1. Air in the clutch hydraulic system
2. Worn slave or master cylinder seals
3. Deteriorated clutch hoses causing it to bulge when pressurized
4. Bent or broken clutch fork
5. Broken pressure plate spring plates
6. Rusted tranny input shaft splines causing the clutch disc to hang up
I had the same problem on mine, and bleeding solved the problem. Of course I decided to replace master and slave cylinders for a more lasting trouble-free driving experience on my high mileage C2.
Good luck

[kurquhart]

+1 on the clutch. Nice list, bazar01.

[Bertie]

Thanks Bazar01, quite a comprehensive list!

Any thoughts on which is most likely to cause the problem when the engine's cold?

Is bleeding the clutch system a simple thing to do? I have a reasonable workshop and would undertake an oil change but I've never gone near the clutch.

Bertie

[bazar01]

Originally Posted by Bertie

Thanks Bazar01, quite a comprehensive list!

Any thoughts on which is most likely to cause the problem when the engine's cold?

Is bleeding the clutch system a simple thing to do? I have a reasonable workshop and would undertake an oil change but I've never gone near the clutch.

Bertie

Most likely black and rusty clutch fluid which damaged the slave cylinder seals allowing fluid to leak and introduced air in the system.
Bleeding the clutch can be a simple job turned to a nightmare when after using up two bottles of fluid, you still can't get the pedal to rise and pressurize. Been there !!!
Bleed the clutch slave first. If after inspecting the slave you found fluid leaking, don't waste your time bleeding. Get a new set of master and slave cylinders from our host. Good luck.

[Don Plumley]

Assuming you don't have a C4, the procedure the flush or replace the slave cylinder is pretty easy. Here's the DIY for the flush, here's the DIY for the replacement.