Bleeding the Clutch Slave Cylinder

[LeonardU]

I need to bleed the clutch slave cylinder on my early Contemporary Cobra and need help. I tried to bleed it myself with a Mighty Mite and it didn't work. I have been told that I need to bleed the master cylinder first manually by using the clutch pedal, but I can't locate a bleed fitting on my master cylinder for my clutch. Has anyone used a brake bleeder that works with a air compressor to power bleed the system? Any help would be appreciated. The weather is great and the car sits on stands. I need to get the Cobra on the road. Thanks for any help.

Len

[jhv48]

I just had to post this to this thread.

After hours of bleeding the slave cylinder with the car jacked up and my wife operating the clutch while I open and close the bleeder valve, I had an epiphany!

I remembered someone on this forum suggested that the way he bled the system was to crawl under the car, loosen the bleeder valve and let it drip into a drip pan while he went inside and had a beer.

It works! I opened the valve, let it drip into a pan, came out and filled the reservoir every 15 minutes before it went dry, and after two full bowls of fluid, climbed under the car, tightened the bleeder and it was done. Clutch pedal is just as strong as it ever was.

Thank you, whoever suggested this method. You're a genius!

[patrickt]

I remember that; I was skeptical at the time. Have you tried it on your brakes?

[Excaliber]

Often, especially when bleeding a new and totally empty hydraulic system, I remove the bleeder valve entirely. The master cylinder usually does not have a bleeder valve, you open one of the hydraulic lines to bleed it. If it's brand new and was previously dry (no fluid) AND I forgot to "bench bleed it" (or you don't know how to do that) then I remove the line entirely.

With the MASTER (always start here first) hydraulic pressure port (the line was removed) now completely open you have a couple of choices. You can use the fill it up and go have a beer method, (mostly doesn't work for the Master, often works well for the slave though) or you place your FINGER tightly over the exposed hole and use your finger for a bleeder valve. So the wifey is pumping on the pedal and eventually you begin to "feel" a little pulse, or some pressure. Have your assisstant hold the pedal down while you ever so gently loosen your finger hold enough for some pressure/fluid to come dribbling and later squirting out the hole. CRITICAL next step: Hold your finger tightly back over the hole (like you have closed the bleeder valve) while your assistant releases the pedal pressure. Now HOLD for a few seconds or longer with the pedal pressure released to give the brake fluid TIME to be drawn into the empty cavities and areas internal to the master cylinder. Repeat until your are getting so much pressure it is impossible to stop the fluid from squirting out with just your finger. Put the line back in the Master, it is "ball park bled" and internal cavities and voids are filled with fluid. You are now ready to focus on the slave (clutch, brake, whatever). Same thing, remove the bleeder, cover the hole with your finger and YOUR finger becomes the bleeder valve. When you can't hold the pressure anymore, your ready to install the bleeder valve. Or, go have a beer and let it bleed first, sometimes that doesn't work though, depending of various systems. Almost always works great (have a beer method) on clutch slaves though! Do the clutch master if it's new using the finger method first.

If this bleeding procedure takes a few hours, your doing it wrong, period. Most likely it's because you have SO MUCH air you can't get started with a good bleed. Hence, the "remove the line or bleeder valve entirely and use your finger method" to get in the ball park so you CAN bleed the system!

I never was a big fan of power bleeders using air pressure or whatever, just not my cup of tea. I prefer to hire a neighbor kid, if that's what it takes (give him $5) and let him pump away at the pedal. Unless your going to be doing this for hours, and if thats the case, "your doing it wrong".

You MUST remove the line or the bleeder valve entirely if your going to use your finger. Putting your finger OVER the end of the bleeder valve will not seal the port. It will suck air back in and you will be there "for hours" trying to figure out why this isn't working. Using a plastic line placed over the bleeder valve and the other end of the line in a can of fluid is also a pretty screwed up method. These "self bleeding kits", as they are often called and seen on late nate TV informercials are generally a crock and your throwing away your money. As often as it DOES work (conditions have to be PERFECT, they seldom are) it DOESNT work and again your there for hours trying to figure out how come you can't get the air out and the fluid in!

[jhv48]

Originally Posted by patrickt

I remember that; I was skeptical at the time. Have you tried it on your brakes?

Haven't tried it on the brakes. Due to the length of brake lines, could take a long time to gravity feed through all four lines.

[Excaliber]

Especially if their NEW and EMPTY lines. Then you really only have two decent options: Power bleed using air pressure (risky, fraught with potential problems) or the "finger over the hole method", which is surprisingly quick! I'd bet quicker than a pressure bleed!

[mickmate]

I use a line on the slave bleeder and get the other end up to a decent height in the engine bay and keep it submerged in fluid.

[jhv48]

I was actually purging the master cylinder, slave cylinder and connecting lines of old fluid and replacing it with fresh fluid. Not just trying to eliminate air in the system.

[Excaliber]

mickmate, that method works well, IF, the threads around the bleeder valve aren't letting air back in the system and there is an air tight seal on the tube over the tip of the bleeder valve. Sometimes it's tough to get both to work.

Jim, purging is a CLASSIC case of when I pull the bleeder valve out and use the finger method. You can get a LOT of fluid out with every stroke of the brake pedal. When you see the fluid color start to clear up or change, then switch back to the bleeder valve method. I recently bled both the ERA and my auto trailer using the finger method to purge the system of old fluid. Worked well, I was done in no time. Of course it is a two man job, that can be a serious downside sometimes.

[LeonardU]

I finally purchased a Motive Power Bleeder with the 45mm adapter for my reservoirs any it is wonderful. The price is $50 and it so simple to use. It is a 2 gallon pressurized unit that pumps up the pressure in your reservoirs to 10 PSI. You open the bleeder on your slave cylinder and all the old fluid and air is forced out of your system. My clutch is better than ever. It is a 1 person job, takes no time at and there is no mess. I highly recommend the unit.

Len

[Jimbocobra]

Here are the step-by-step instructions with pictures for bleeding for the Master/Slave from Bill Littleton, the midwest Backdraft Dealer (gcperf.com). He is one of the most helpful guys around. He wrote a tech article, I found it extremely helpful hope you do as well: http://gcperf.com/march10newsletter.html

[Sal Gerace]

I like to pressure bleed from the bleeder on the slave.this method has given me the best pedal so far. I use a pheonix system but I am sure other companies make this style system. Pressurizing from the resevoir down does not work at all on the clutch.

[LeonardU]

I have tried gravity bleed, pedal bleeding and vacuum bleeding with unsatisfactory results. My pedals are not floor mounted and the reservoirs are not high enough above the master cylinders. I don't know what you mean by bleeding from the bleeder on the slave. I am not familiar with the Phoenix system; would you describe it for me. To say that pressurizing from the reservoir down does not work at all on a slave cylinder may be an overstatement on your part. It is the only method that has worked for me. I am not an expert, but a novice who is trying to learn.

Len

[Sal Gerace]

The Phoenix system like other pressure bleeders out there is a pump that pushes fluid or pulls fluid through your brake or clutch system. I have used the pump to push fluid from the bleeder valve back up to the brake resevoir. The way it works is it has a jar that you fill with brake fluid and the the pump attaches to the jar via a small hose and where the fluid exits the pump there is a small hose that attatches it to the bleeder. As you pump the handle it draws the fluid out of the jar, through the pump and if attached to a bleeder fitting (that is open of course) up through your hydralic clutch system pushing any air from the slave on up out to the resevoir. This method seems to work best for me because as it pushes the brake fluid through the system it not only pushes air out but also pressurizes the system giving a very firm pedal.