Luis de Prat

I spent the weekend catching up on things I needed to get done to the 951, including replacing the fuel filter, adjusting the headlight mechanism, replacing various bits of hardware, cleaning the engine compartment, etc.

Since doing the rear brakes a few weeks ago I noticed the clutch pedal began to have an annoying squeak. Someone suggested that I may have gotten some air in the system which made sense since I remember taking out a bit too much brake fluid from the reservoir which probably let air in.

Anyway, today I decided to bleed the clutch from the slave cylinder. I had a helper push the clutch pedal in all the way, attached a hose to the slave cylinder bleeder valve with the end in a jar with 2" of brake fluid, and at first the bleeding was going well until suddenly the clutch pedal slammed itself down against the floor and no amount of bleeding would make it come back up.

The only time I've ever had a clutch slave cylinder go bad this was exactly what it did: snap down and not come back up.

Does this mean the slave cylinder is broken?

Wallace

this may seem obvious but, did you make sure to keep the fluid resevoir topped up?

if not, it would've sucked a whole ton of air into the system and caused the pedal to drop to the floor.

Tom M'Guinn

You sucked air into the system, at the slave or reservoir. Unless you need the car in the meantime, I'd just put your tools away, order a MOTIVE power bleeder (well under US$100) and some superblue, and wait for it to arrive before trying again. You can sepnd hours and hours trying to bleed the clutch the old fashion way, or minutes using the MOTIVE.

If you need the car and can't wait for the MOTIVE to show up, a hand vacuum pump can help by sucking the air from the slave. Archives are brimming with other suggestions/approaches.

Darwantae951

It's either the slave or the master cylinder. Just replaced a master cylinder that was shot in my friends 944.

-Darwin

Luis de Prat

Reservoir was topped up at all times, but the hose I used for bleeding may have slipped out of the jar momentarily.

I've wanted a Motive bleeder for years, but never got around to ordering one since I'm in Europe.

I need to move the car fairly soon. Hand vacuum pump? I'll check the archives again. Thanks for the replies just the same.

Cone_eater

Did it slam down on its own or fall? Does it have pressure against pulling it up?
Try to bleed, then seal the valve on the slave and pull the petal up. Pump it 20 times and bleed again. You just lost pressure in the lines. It’s all still good. I ran into the problem a few weeks ago.

Tom M'Guinn

Lots of auto parts stores sell the MityVac, like this one:

http://www.mityvac.com/pages/products_hvpo.asp

But if you have to order it, just order the MOTIVE instead. Hard to believe someone wouldn't carry it in Europe somewhere, but worst case DHL shouldn't take that long even from the states... It will immediately be your favorite tool.

Tom M'Guinn

Actually, before Motive starting selling them, people used to make their own Motive bleeders using a bug spray bottle. EDIT: Here is a link:

http://www.bmw-m.net/TechProc/bleeder.htm

Cone_eater

That a cool home made tool!

Luis de Prat

Thanks, Tom. In lieu of the Motive bleeder, I had been wanting to make this tool for some time, but hadn't seen a comparable spray bottle at local hardware stores.

Back to the bleeding, the pedal does snap down with force. I am tempted to go back and try bleeding it again but get lost in the sequence -pedal down, open bleed screw, close bleed screw, pedal up?

The front of the car is presently raised on jack stands, which I doubt is helping getting the air out, but it's the only way I can get access to the clutch slave bleed valve...

Cone_eater

take the starter off to access the valve

Luis de Prat

I had good access to the valve with the starter on. Just not sure if I should lower the front and jack up the rear instead? Which side did yo have up?

Tom M'Guinn

Close bleeder. Pedal down. Open bleeder. Close bleeder. Pedal up. Top off fluid. Pedal down. Open bleeder. Close bleeder. Pedal up. Top off fluid. Repeat over and over. If you have a mityvac, just keep a vacuum on the bleeder when you crack it open. It will suck the trapped air out a little better than pumping alone.

alex

Free tip- don't have your pregnant wife help with the pedal side of things. She's still complaining and that was 5 months ago. Also, sometimes this just takes a long time, I don't know why. Keep on trucking. Eventually, it'll firm up.

Luis de Prat

I finally got this straightened out.

Want to thank Jon Wallace for the correct diagnosis: it was air in the clutch cylinder, and Tom M'Guinn for suggesting a pressure bleeder. I found a way to make my own following this classic write up: How to make your own pressure bleeder, and it worked!

One last question I have: in order for the pressure bleeder to work best, it needs to be above the brake master cylinder at all times, right?