Clutch slave cylinder bleeding 101 by jaybquick@JHM:
Being that I sell alot of transmission related parts (shifters, linkage upgrades, clutches, flywheels, transmission rebuild kits, etc.) I have been getting more and more calls with tech questions regarding our good friend the slave cylinder.
So I figured I would summarize the common problems and the best bleeding procedure for the DIY guy. Obviously a pressure bleeder is the OEM recommended way, but I doubt many of you have those.
IMPORTANT TIP New as of 5-11-09
We have found that if you try to bleed the clutch with the car NOT completely level. Like if you just jack up the front. You will almost NEVER be able to bleed it completely or will make it take forever. This traps air bubbles in one of the upper corners. So make sure the rear of your car is level with the front of your car and if not level even a little higher than the front. The key is to not have the front higher than the rear. We have always bled ours when the cars were level and routinely do it in 5 minutes or so. Well recently I was lazy and tried to do one with just the front of the car up and I couldn’t get it to bleed for me no matter what I did. I thought about it and it hit me why. So I jacked the back of the car up and BOOM, it bleed quickly. Hope this new tip helps some that are struggling.
NOTES:
The Slave Cylinder uses the same reservoir as the brakes, which requires a Dot 4 brake fluid. And of course we sell them here --> Clutch Slave and Master Cylinder
INSTALLING PROPERLY:
This is a commonly improperly installed item during a clutch job or any trans pull. First off I highly recommend not unhooking the hose from the slave unless you are replacing the slave cylinder. I recommend you just undo the 1 6mm allen(hex) bolt that holds it in place and leave the slave in the car still attached to the hose. This will save you the pain of bleeding. IMPORTANT: When you put the slave cylinder back in the trans (only after the trans is completely bolted back up to the motor) it should not slip in super easily especially if it has not been replaced and has no air in the system. You should also always start by putting a thin layer of grease on the outside of the boot where it goes into the trans so it does not catch and hang up when putting it in, this helps a lot. You have to make sure the pushrod goes into the clutch fork, this is very important or you can pop the piston and rod clean out of the slave cylinder and run the risk of it falling into the bellhousing and need to be removed by pulling the trans again. Then have to buy a new one, since you don’t want to risk it leaking once you figure out how to reassemble it, if you even can. When it hits the fork you will feel steady resistance and takes time to get it to compress and push fluid back into the brake reservoir (be patient and keep pressure, it takes strength to do this). Once it is in, it will drop into a catch on the trans that will hold it in place, at this point just reinstall the 6mm allen (hex) bolt and tighten it down. If it goes in super easily you most likely missed hitting the clutch fork with the push rod. However, if you have a new slave cylinder that you installed or have air in the system for any other reason it will be pretty easy to install. So another way to confirm engagement is push on the clutch pedal with your hand, not foot. It should give you resistance if it is not full of air. It should also feel funny the first time if you have a SAC style clutch pressure plate (OEM or RS4 type) since the SAC mechanism is setting itself. If you push the clutch pedal and it feels like it bottoms out and gets very hard, DO NOT FORCE IT. You are feeling the piston bottom out in the bore since the pushrod is not engaged into the shift fork and if it you press it one more time, POP goes the piston and rod out of the slave cylinder. Hope this info helps you with your transmission and or clutch install.
BLEEDING
** NOTE: You usually have to crack the bleeder screw .5 to 1 full turn to get any fluid/air to come out. **
Similarly to Brakes, Clutch hydraulics (slave or master) need to be bled after being opened or when a component is replaced. Also, you always need to make sure the brake/clutch fluid reservoir is full and stays above the level of the hose that comes out the side of the reservoir, this hose is what feeds the Clutch Master Cylinder so if the level gets below this hose you will then start sucking air into the clutch hydraulics and have to start your bleeding procedure all over again.
NEW CYLINDERS OR FULLY DRAINED SYSTEMS With all that air in there, it will just aerate the fluid and never bleed if you try the old pump it up and then hold it to the floor routine and then have someone crack the bleeder after. INSTEAD crack the bleeder FIRST, then push the pedal to the floor and hold it. Then while still holding the pedal to the floor close the bleeder. Then pull the pedal up, only once the bleeder is closed. Repeat this procedure several times until fluid comes out. Once fluid comes out then do it at least 2 more times to be careful. At that point you can switch to the old pump it up and hold it to the floor method. To do that, you just pump the clutch pedal several times, then hold it to the floor. While the pedal is on the floor crack the bleeder and then close. Repeat this 2 to 4 times just to be sure. At this point the pedal should feel great. Once you think you have it, give it a 30 minute break to make sure any incedental aeration settles down. Then come back and bleed it one more time, if you hear or see air do it again. If at any point you start with the pump it up first then crack it method you should give it a 30 minute break to let the aeration go away in the fluid. Once you aerate the fluid and just keep trying, you will be there forever and it will never bleed properly. PATIENCE AND PROPER PROCEDURE ALWAYS PREVAIL.
FINAL BLEEDING IF YOU ONLY HAVE A LITTLE BIT OF AIR IN THE SYSTEM
For this the old pump it up and hold it to the floor method usually works fine. To do that, you just pump the clutch pedal several times, then hold it to the floor. While the pedal is on the floor crack the bleeder and then close. Repeat this 2 or more times just to be sure. At this point the pedal should feel great. Once you think you have it, give it a 30 minute break to make sure any incidental aeration settles down. Then come back and bleed it one more time, if you hear or see air do it again. NOTE: Once you aerate the fluid and just keep trying, you will be there forever and it will never bleed properly. You must step away for at least 30 minutes to get the fluid to not be aerated.
GRAVITY BLEEDING
This is a great technique when you replace the slave cylinder to save you headache and time.
- Get the new slave cylinder installed; bolted in completely and connected to the hose.
- Make sure the brake fluid reservoir is full (clutch master and slave share this reservoir with the brakes)
- Crack the bleeder screw at least 1 full turn (360 degrees) to 2 full turns (720 degrees0
- Put a drop pad or rag below it on the ground.
- Take a break and within 5 to 30 minutes you should see fluid dripping out.
- Once the fluid starts dripping tighten down the bleeder.
- It is now about 90% ot 95% bled and now you may only have to do the above bleeding procedures once or twice. This saves a lot of headache and aerated fluid.
I hope this info can be of use to you guys, this info is free as a courtesy for your continued help and support of my business.
NOTE: All JHM customers that buy their parts us get this kind of knowledge and tech help. So be careful who you buy from. Can you call on them for help when your car is apart and you are stuck??? Also, due to our higher email(preferred contact method) and call volume as of late we obviously have to help our paying customers first and sometimes can’t get to other emails or calls for a day or so. I would love to help everyone but I can’t so I do the fairest thing I can, help those who help me.
Thank you everyone for your continued support. Keep checking out our new store for new aftermarket and replacement parts. We are adding new products every week and are seeking out more suppliers and new accounts. If it is not on our store yet, we can most likely get it within a few days at a great price.
http://www.audizine.com/forum/showthread.php/234720-Clutch-Slave-Cylinder-Install-Tips-and-Bleeding-101-by-JHM
