Clutch

Omathisen · #1 (**permalink**) 08-07-2008, 06:41 PM

Hi,
Next project: My clutch pedal has slowly been going soft, making it harder to get the car in gear. By bleeding the slave cylinder (first time I did this, the fluid was black), the clutch is hard again and works fine - 200 to 300 miles and then starts going soft again. I assume the problem is the slave cylinder? Any ideas? Any trick to changing this?
Thanks for any help. Learning my way from project to project.

GlynMeek · #2 (**permalink**) 08-07-2008, 06:57 PM

What type of slave have you got? Is it one of the 'infamous' Wilwoods where the piston will slowly unscrew from the rod?

Glyn

Roush #1 · #3 (**permalink**) 08-07-2008, 07:14 PM

Omathisen,
The dark fluid is sometimes an indication the fluid is being overheated....maybe the hydraulic lines are too close to a header?
Jody

Tony Radford · #4 (**permalink**) 08-08-2008, 02:46 AM

I've been plagued with this issue for years. The black fluid is likely caused by aluminum being rubbed into the fluid - like the black residue that accumulates on a rag while polishing aluminum. It eventually destroys the O rings in the master and slave. Also, if you use DOT5 synthetic fluid, the same thing can happen. Check both to see if fluid is getting around the piston seals. Replace one or both depending on what you find. It will just keep getting worse. It it's not the fluid, you may be overdriving your master by exceeding the max travel.

strictlypersonl · #5 (**permalink**) 08-08-2008, 03:57 AM

The problem is most likely the clutch master cylinder drawing in a minute bit of air each time it's released. A bad slave cylinder will leak fluid out the end.

Both the master and slave are iron, not aluminum. Sometimes the rubber feed hose will turn the fluid darker. No big deal.

Tony Radford · #6 (**permalink**) 08-08-2008, 05:14 AM

Maybe your slave and master are different. I'm running Wilwood master and Raybestos slave. Both are cast aluminum. Not iron. My system has no hose.

CobraEd · #7 (**permalink**) 08-08-2008, 06:21 AM

Put a cable on it !!!!

.

ERA Chas · #8 (**permalink**) 08-08-2008, 06:28 AM

12 years ago I lost the pedal about 2 miles from home. Shut the car and let it cool 20 minutes and pedal returned enough to get home.
Inspection showed black fluid. Bled and refilled then insulated the line (which nearly touches the head and exhaust port and is just above headers) from reservoir to master with Firesleeve. No more overheated fluid. Ever. Bleed clutch and brakes every season.

Omathisen · #9 (**permalink**) 08-10-2008, 12:30 PM

Hi,
Thanks for all the input. Bled the clutch today. Fluid that came out was dark gray, nearly black. Clutch is hard again.
Let me answer each of the contributions as best as I can:
I do not know what kind of slave cylinder I have; there is no identification on it.
I doubt it can be overheated, since I have had the car for 10 years and this issue only started last year. (I thought I would start by bleeding, before moving on to replacement, etc.) But I will look up Firesleeve.
There does not seem to be any leakage. The fluid level stays where it is and the slave cylinder is dry.
As for air, where would it come in?
And last year, when the clutch first went soft, and I had problems getting the car into gear, it helped to shut things down and then start up again with everything working (at least while I parked it).
First time, I bled it, the fluid was all black; the second time it was only a little discolored; the third time it was clear; and now it is dark again.
And finally, I have no clue what "putting a cable on it" means.
I am hoping to fix this myself but will go to a shop if I cannot.

patrickt · #10 (**permalink**) 08-10-2008, 12:43 PM

Quote:

Originally Posted by Omathisen

HAs for air, where would it come in?
And last year, when the clutch first went soft, and I had problems getting the car into gear, it helped to shut things down and then start up again with everything working (at least while I parked it).
First time, I bled it, the fluid was all black; the second time it was only a little discolored; the third time it was clear; and now it is dark again.
And finally, I have no clue what "putting a cable on it" means.
I am hoping to fix this myself but will go to a shop if I cannot.

Ignore the cable remark; it was a joke. If you can make the problem go away, even for a short while, by bleeding the system then that confirms that air is the problem. A bad master cylinder can actually suck a little air in past its seals. Don't let the color of the fluid mislead you, air is your problem. I would just go ahead and replace the master cylinder with a nice Tilton and I think your problems will be gone.

Omathisen · #11 (**permalink**) 08-10-2008, 01:44 PM

I am leaning towards a new slave - Tilton sounds good. I guess the cable joke is on me. Nice sound effects by the way.

patrickt · #12 (**permalink**) 08-10-2008, 01:58 PM

Neither cylinder is all that expensive. You might think of just replacing both at the same time. It's gotta be one or the other.

Omathisen · #13 (**permalink**) 08-12-2008, 06:32 PM

Easier said than done.
I was going to order a master and slave and replace both - but what kind? Is there a model number? Tilton's website did not make me any smarter and my ERA manual does not specify types or models?
I asked Tilton but have not heard back yet.

cobred · #14 (**permalink**) 08-12-2008, 06:40 PM

If you call ERA with the car number they may be able to look up the part numbers that were used at the time your car was built. Who knows, they may still use the same ones.

patrickt · #15 (**permalink**) 08-12-2008, 06:59 PM

Currently for a Master Cylinder they use BMW 2152 1104 510 or the larger
Tilton 74-875U (that's what I have on mine, allows for a shorter pedal travel with no noticable increase in pedal effort). The current slave is BMW 21521104269. Wouldn't hurt to call them to confirm the right cylinders for your number, tho.