Sam H.

Can anyone help with a preliminary diagnosis before mechanic sucks up copious amounts of my cash?

Pulling my '88 S4 into my driveway yesterday, I depress clutch pedal, and boom, it goes to the floor. No return action at all. I park it. No huge puddle underneath, a couple new drips of something yellowish, a little funny burnt smell. Engine runs fine. Clutch pedal stays at the floor. I can pry it back up with my hand, but when depressed, it stays on the floor.

Anything I should look for? Any ideas what the damage is$$$$?

Rez

Clutch master? Clutch master is my thought only because hydraulic fluid may have dripped on the hot engine and hence the smell. Clutch master isn't that expensive, just a PIA to get at it.

GlenL

The black hose running to the slave.

Garth S

Any loss of level in the reservoir?

MikeN

Could be the fluid supply hose from the brake master cylinder reservoir to the clutch master. It it is a "blue" (or should be.....braided blue cloth covering it) hose leading downward from the reservoir to the master. If it breaks or splits it will cause the problem(s) you are seeing.

Sam H.

No noticeable loss in fluid in the reservoir. Still close to the "MAX" mark.

Sounds like the problem is either a leaking hose or a bad clutch master cylinder. Those things I can probably afford.

I have to take the car in for its timing belt/water pump replacement, and I'll have them replace the leaky oil pan gasket and oil filler neck gasket while its there. Seems like the car isn't happy unless I spend about three grand per year keeping it up...

JE928Sx4.

Same thing happened to me this weekend. In my case there was only a little bit of fluid visible in the in the interior under the pushrod. There were no leaks under the car (check of the blue and the black hose is always good to do at this point though). In my case, besides some fluid leak, the spring inside the pedal also broke into about 5 parts. Luckily I was headed to Dr. Falkenburg's to do some A/C work at the time. Full on failure was gradual and it finally gave up the ghost in his driveway.

You can disassemble the clutch master cylinder with it installed in the car.

Remove the driver side carpeting.

Pull the clip that holds the pushrod on the pedal and pull the pushrod out.

Pry the bellows cover off the end of the MC.

Remove the snap ring holding the piston in the MC. If the spring is intact, the piston will probably pop out a bit at this point. If not, use a pressure bleeder to slowly push the piston out of the MC (use two people regardless so you don't gush brake fluid all over your interior).

You have two options now. Get a new brake MC and remove the guts from it and reinstall in the car. Or, if the spring is still intact, you can buy a Clutch MC rebuild kit to replace the seals on the piston from NAPPA for $22.95 (at NAPPA online part number UBP1899).

When you reinstall the Clutch MC piston, use a pressure bleeder. When you see slight seepage around the piston, you have bled the system. Remove the pressure bleeder, and push the piston in and secure with the snap ring. Reinstall the bellows and pushrod. You should have a rock hard pedal at that point.

Thanks to Dr. Falkenburg, we cannibalized Barney and replaced the guts in my car to get me back on the road the same day.

deliriousga

All of the above unless you have had some work done lately that would requre removal of one of them. Somebody may have disconnected the slave or a hose and not reconnected it or bled it correctly.

I don't know what a mechanic would charge for the time. Mine have all been DIY so I'm sure you would not want to pay him for my times.

I'm currently doing the master rebuild just mentioned by JE928Sx4 to see if it gets rid of the last bit of air that's getting in there.

JE928Sx4.

Exactly the conditions I had. Read above. Very simple fix. The shop will ream you.

Dave Howerdel

Through all of the master/slave cylinder failures I've been through, I've always been able to lift the pedal and get the clutch to disengage (at least partially) with a quick stab at the pedal.

The only time I lifted the pedal and found no resistance upon depressing it again was when my realease bearing gave out. I guess burst hose or catastrophic failure of the master/slave could cause this but I suspect there would be quite a bit of fluid in the housing or firewall.
Just my experience.

Randy V

Hey, Sam - another SD 928'er. What shop do you use in SD?

Some good advice from the guys above.

karl ruiter

I've had two strange problems cause this. In one case the clip that holds the throw out bearing to the pressure plate failed and in the other case the spring inside the cluch master cylinder failed. Neither is expensive but either is a pain.

hupp

Before diving into the master, I would take a good look at the slave first. Air in the slave due to bad seals can have a drastic effect. Pop of the small plastic inspection cover and take a look. Any fluid in the lower bell? Has the slave rod popped out of the release arm dimple?

No appreciable loss of level in the master - The funny/burnt smell is probabily due to your oil leaks.

Just a couple of easy things to check before moving on the the PITA stuff.

JE928Sx4.

The fact that he has spotted even the slightest amount of fluid inside the car indicates the Master has already failed. It's the first place to look. I'm betting he finds a broken spring as well.

deliriousga

Go for broke. If you're going to lift the car to check the slave and it's never been replaced, just replace it. $75 new at the big 3. It's a lot easier to just replace that and refurb the master cylinder (you don't want to change that puppy) and bleed the system one time. Check the black hose to the slave line for leaks while it's up and replace it if there are any or if it feels like it's bulging anywhere.

Personally, I've been more frustrated doing this a little at a time over two months. First the slave and it worked fine for awhile. Bled it 3 times for short term fixes then found the master starts leaking a little so it's time for that. While I have it in the air and fluid out of the system, the rubber slave line will be replaced. The way I see it, 20 year old rubber is going to be worn out whether it's used or not. I'd rather drive it than spend an hour lifting the car so I can bleed it again, and again, and again while trying to figure which rubber part failed this time.