924Board.org

[skytrooper]

Anybody have a quick down and dirty version of bleeding the clutch cylinders ? I do not want to replace them until I have a chance to bleed them, just to be certain that they might not still be fine.

Oh, if it makes any difference the car is a '87 924S

Thanks

[joecitizennn]

what is wrong with them in the first place? Bleeding is not going to fix screwed up seals.
To bleed, remove clutch/brake reservoir cap, remove the little plastic cup that sits inside (while not completely necessary it makes filling easier.) Top up reservoir. Find a reluctant assistant. Put car on lift or jack stands. One person crawls under the car and attaches a clear plastic hose to the nipple on the slave cyl. The other person operates the pedal inside the car.
They say to fill the bottom of a container with clean brake fluid and make sure the end of the hose is immersed. I suppose to keep air from accidently re-entering the system. I dont usually do that. i just stick the hose in a jar or pan. With a clear hose you can see if an air bubble is traveling back up to the nipple.
Person under car opens nipple by unscrewing it a fraction and shouts "down" Person in car presses down, and old fluid is expelled from bleeder nipple. When the fluid stops flowing, person under car closes bleeder nipple by screwing it down and shouts "up" and person in car lets up drawing fresh fluid into lines. Keep at it untill you can see clean new fluid flowing through hose. *
I usually have my wife help me, but if you dont have anyone to help, you can buy a bleeder valve. It either attaches to the bleeder nipple or it replaces it with a nipple containing a one way valve. Using this system you just loosten the valve and pump the pedal until clean fluid comes out, close the valve and you are done.

*Make sure you constantly check the reservoir so you dont draw air into the clutch line when the level drops.

[joecitizennn]

What happens alot of the time with clutch cylinders besides the failure of rubber, is people dont change their brake fluid enough. Brake fluid absorbs moisture, and over time the moisture can damage steel parts with rust. If you take your clutch cylinders apart you are likely to find some pitting. It may or may not be fixable by a hone. Probably not. Before you decide to buy a rebuild kit you should look at your cylinder bores. 2 of the 3 924S clutch slave cylinders I have rebuilt have been badly pitted inside.

Parts to slave cylinder, old parts below new parts.


Pitted cylinder walls

[skytrooper]

That could very well be the problem. I have not removed the cylinders from the car to tear down and see. The brake fluid hadn't been changed in 10 years and it was black. I cleaned out the resevoir, added new fluid, and bled the brakes (rebuilt calipers)...and they work now. I was hoping on trying the same thing with the clutch cylinders also. I do have rebuild kits coming UPS this week sometime.

[Rasta Monsta]

Google "black label powerbleeder". . .it is 1/50th the PITA as other techniques I have seen described here. . .[/code]
_________________
Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[joecitizennn]

You are still going to have to crawl under your car.

[Smoothie]

I find that if you install the slave cylinder pre-bled, all you need to do is pump the pedal (quite a few times, but still easier than crawling under), to finish the job. This eliminates the under-car bleeding step altogether.
-And I just verified yesterday that it works with other vehicles as well. My brother stopped by and the clutch slave in his Ford F150 failed toward the end of his trip, but he made it to the house. This truck has the major pain in the A arrangement that requires the transmission to be removed to replace the slave cyl. Long story short, the new slave cyl was pre-filled and bled by the manufacturer (Hecho in Mexico from parts made in USA and France ) - we installed it and reassembled the truck, filled the reservoir at the master cylinder, pumped the pedal quickly by hand probably 50-60 times, then another 20 or so by foot after it started returning on its' own, topped off the reservoir again, and the job was finished.
I've been doing the 931's hydraulic clutch this way for over 10 years - I just bench bleed the slave cyl, install it (hook up the line first, then position the slaves' rod in the fork, finish tightening the line, then attach the slave with its' 2 mounting bolts and tighten them, then pump the pedal until it comes back..
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[!tom]

[Rasta Monsta]

[skytrooper]

[joecitizennn]

Im confused. You said the bore is fine, but the piston wont come out. How can you see all the bore?

As a last resort you could use compressed air to blow the piston out. There is a spring behind the piston, sometimes you can get the piston out by pushing it down against the spring pressure, and letting it pop back up as quick as possible untill it has worked far enough out to grab ahold of the end of it and pull it all the way out. (sometimes takes a lot of poking) If it is stuck in there, you may have rust. If you do blow it out with compressed air, point it into a wadded up shirt or a pile of rags. That could make one hell of a pellet gun!!

I took apart a 924S slave that was ok, or at least saveable with a hone, maybe 3/4 of the way down, but then there was bad pitting in a ring around the cylinder wall (see above picture look at the awful pitted ring). Right where the pistons rubber seal sits when the pedal is up (car was stored for 15 years). I dont know why the rust chose to start there, but it made the thing unusable.

[skytrooper]

Well, at that point I couldn't see all the bore. What I could see looked pretty darn good...not at all like your example above. I took your advice tonight and poked at the plunger a couple of times....and it popped right out. The inside looks good down inside there also, but I am taking it to work tomorrow where I have all the good tools.

Thanks

[joecitizennn]

Here is a picture of what the master out of the red 87 924S looked like. Yum! Surprisingly, the bore is shiny as glass all the way back. Good thing because it is too small for a 3/4 brake hone. It took me 15 minutes to get the piston out with wd-40, and careful pushing with a rod through the pressure hole on the end.

[img][/img]

[skytrooper]

Yeah, my master looked like that on it's guts too. I did however say the heck with it and bought both cylinders today. The master had a real bad spot in it