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Thread: Clutch bleeding methods.

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    NBMWSsix's Avatar

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    Clutch bleeding methods.

    Buschman's method.

    This is the clutch bleed method I came up with when installing my McLeod Master Cylinder. Other than the M/C itself the tools I needed where: Your Old Slave Cylinder, Dremel tool, GM OEM Spec Brake fluid (only one bottle was needed, but much recycling took place), Mity Vac Pump, Zip Tie, Small Rubber Washer. Ok the first thing I did was to create this little helpful tool. Iíll call it a slave sim. Cause basically itís job is to act like the slave cylinder, open up the hydraulic valve, and allow me to pull the fluid through the Master cylinder in the direction of the slave cylinder.




    I basically removed the female end of the Slaveís hydraulic connection by removing the pin (same pin setup as the M/C) and the connector slid right out. ***Not that you need it for this clutch bleed but if you happen to tear your M/C washer you will find the exact same sort of washer sealing the Slaveís female connector. So you might want to store it somewhere just incase.***



    Save yourself a half hour of frustration and Dremel out the inside of the tubing. It will make slipping the tube over the Slave's hydraulic connector so much easier. Be sure to clean out any and all loose rubber if you do Dremel the inside. I put just a little bit of grease around the tube to help slip it on.



    I placed a small rubber washer in the gap of the female connector. Not so much to seal the tube but just to help get the tube past that gap. The tubing came straight from the Mity Vac kit I got. I just cut one of the longer tubes in half. They are the perfect size for this job. Once the tube is on securely, zip tie it and youíll have an airtight seal.



    Here youíll see the M/C setup to be bleed. Forgive me for using a stock M/C in my pictures, but the McLeod is in and working. Iím certainly not gonna rip it out to take pictures of it.



    So Iíve mounted the M/C horizontally in the vise. Iíve removed the reservoir, but left the reservoir tube and ran it into a plastic container filled with brake fluid. Be sure to keep the brake fluid level above the tube opening at ALL TIMES! Otherwise, youíll suck air back into the system and have wasted all the time you just spent bleeding.



    Now I have the hydraulic line running upwards to help the air get out of the system. This is probably overkill since the Mity Vac is sucking the air out, but it isnít hurtin either. As you can see from the picture, I have my slave sim connected to the hydraulic line and running into the Mity Vacís vacuum container.



    The first step is simple. Pump up the Mity Vac to 5 psi and let the pump pull out the air and fluid. Obviously when your Mity Vacís container get near full empty it into the plastic container that feeds the reservoir tube. Continue to go through this cycle until you donít see any more air being removed. Then, go up to 10 psi. Repeat the cycle until there are no more bubbles. Then go to 15 and then 20 psi. Every time you bump up youíll magically see more air. At 20 psi you might notice the bubbles start to aerate a little bit (kinda looks like soap suds if youíre not familiar). Donít worry about those; weíll get those later. Just try and eliminate the normal air bubbles.



    OK so now onto the second step. A little more complicated, but youíll get all the ďtrapped airĒ with this method. The M/C should be setup exactly the same as in the first step. The only possible change would be the size of the tube inside the Mity Vacís vacuum container. This picture doesn't quite illustrate it so well but you need to connect the tube that ďalmostĒ reaches the bottom of the container. If you were already using that one, then youíre set. If not put that tube in now.


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    To start youíll need to pump the Mity Vac quickly and build up 20 psi of pressure as fast as you can. The Mity Vacís container should be filling fast. Wait till it hits about the halfway mark (the fluid level needs to be at least an inch to an inch and a half above the bottom of the tube so no air is sucked in). Once your fluid level is high enough slowly pump the M/Cís clutch pedal rod in all the way and slowly let it out. Youíll notice a ton of air released at this point. When you pump the clutch pedal rod in, the fluid flows into the container rather quickly. When you let the clutch pedal rod out it sucks whatever air and fluid are in the the Slave Sim tube back in (this is why itís important to have the fluid level above the tube so no extra air is sucked in). The Mity Vac will not be able to suck any fluid unless the clutch pedal rod is completely released. Once the rod is back out the Mity Vac will get all those air bubbles you just shook loose. (You can use the trigger on the Mity Vac to quickly release pressure so your fluid level does not go past the top of the Mity Vacís vacuum container) Continue to do this till you donít see any more bubbles.



    There is one spot left where air can still hide in the M/C unit. To get to these bubbles we have to change the setup a little bit. First off remove the Slave Sim from the Mity Vac (Weíre done with the Slave Sim) and disconnect it from the hydraulic line. (The clutch pedal rod should be rock solid and youíll not be able to push it in with the hydraulic line closed)



    Remove the Reservoir tube from the container and reinstall the actual reservoir. Now you need to find a way to hang it up so that it sits vertically (I mangled a couple of coat hangers for this duty) On the Mity Vac attach a different tube in place of where the Slave Simís tube was attached. To that tube you need to find one of those little nozzle accessories. You can see from this photo that it needs to be one of the nozzles that look like a pencil tip.


    As you can see from this picture, that nozzle has to fit ďinsideĒ the small hole at the bottom of the reservoir.



    With your hydraulic line disconnected and closed and your reservoir filled and vertically suspended you are ready for the Mity Vac. Before inserting the Mity Vac be sure to fill the tube holding the nozzle with brake fluid. You donít have to fill it up all the way, but at least 4-5 inches worth of brake fluid in that tube (about the halfway mark). Snuggly insert the Mity Vacís nozzle into the small hole at the bottom of the reservoir. Your setup should look something like this by now:

    Pump the Mity Vac up to 20 psi and you might find a few bubbles pulled out. Be sure the nozzle is snuggly in that hole; otherwise youíll just pull fluid out of the reservoir. I want to get any air that might be trapped in the reservoir tube or inside the M/C. Once any bubbles are pulled you can use the trigger to release the pressure and try it again. Keep doing this till no bubbles are pulled. Be sure to always keep at least 4-5 inches of brake fluid in the Mity Vacís nozzle tube, else when you release pressure air can get sucked right back into the M/C.

    Youíre done bench bleeding. Make sure the Reservoir is filled enough, put your moisture lock back in and recap the reservoir. Youíre M/C is now ready to install back in the car.
    The last stage of this Bleed might seem redundant, but many times air can hide in the slave and creep it's way back up. Plus this step is valuable to you when a week or two down the line you feel a little mushiness in the top travel of the pedal. Well forget pulling the M/C back out. You can just hook up the Mity Vac to the resevior and reverse pressure bleed the system while all components are installed in the car.



    As you can see you'll setup the Mity vac the exact same way as you did in the final stages of the bench bleed. However you can use the clutch pedal to jimmy stubborn air bubbles lose. Another trick I learned after doing this bleed method a few times is in this stage if you remove the canister from in between the Mity Vac and the Resevior you can hold 20 psi all day long. Just make sure to always have the pump elevated as you don't want fluid being sucked into the unit. When relieving presure via the trigger, do it slowly so fluid isn't sucked up.



    After pumping the Mity Vac up to 20+ psi, you'll notice tiny bubbles are still being removed. Some of this air was freed when you banged the M/C back into place and some is coming up from the slave. After the bubbles thin out try pumping the clutch pedal in very shallow strokes(just the mushy section up top, maybe 2" of travel). Do this about ten times then one time very slowly all the way to the bottom. If the clutch pedal sticks to the ground, don't worry, sometimes the 20 psi from the Mity Vac can do that because of the reverse pressure(least, that's my guess). Continue this method till it becomes difficult to actually see the air bubbles.



    Remember this last stage you can do in 15 minutes anytime you feel the clutch pedal is shifting funny or the engagement point is moving around. After the car has sat all night the air tends to sit higher and is easier to get to. That's typically a good time to do this "maintanence bleed".


    That's it, you're done! You should be able to just start her up and start bangin gears!

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    Ramos method

    Parts needed:
    1. Mityvac - can be found for around $30 at Sears, Harbor Freight Tools, Autozone, Advanced Auto Parts, Orielly's, etc.
    2. Female end for the slave - Taken off the old slave or you may need to contact any local shops that might have some laying around. You may also find one from someone on this board. Worst case scenario is to remove your slave and use the female end from it.
    3. Pickle jar - Couple bucks from your grocery store. Eat pickles, rinse and dry the jar. I chose Vlasic Kosher pickles. Use a drill or dremel to make the holes, use a couple of the tips from the Mityvac and superglue them in.

    Similar to Buschman's method I use a mityvac with my process but, with a couple differences. You don't need to remove the master out of the car and I used a pickle jar to hold more fluid and maintain about 25 psi for a more complete bleed.

    Here is where it starts. You are pulling the line up through this area.

    Once you get the line pulled up fully it should stick out about this much.



    This is the fluid I am finishing with. I flushed the system with regular Dot 3 until it ran clear with virtually no bubbles. Then I put in the Dot 4. It has a higher boiling point. 446 degrees.




    This is the jar I used to setup my custom bleed setup. It holds about 3 bottles of fluid and keeps the psi for almost the entire time it is filling. The bottle that comes with the Mityvac is much to small and you empty it frequently which makes the bleed process take much longer.





    Here is everything we are going to use. As you can see the jar is quite a bit larger than the bottle.



    I connect the line to the master and used a ziptie to hold it in place on the end of my hydraulic. Don't do it too tightly or it will not allow a good flow of fluid thru the line. We do this because we want the least resistance for the air to get out of the line.



    Here is the setup I had. It worked very well.



    This is probably the minimum psi to get all of those stubborn air bubbles out.



    That psi pulled this out of the system. Nasty icky...



    Starting the process.



    Now you will want to have a few bottles of this on hand to ensure that you keep the resivoir full during the process. If it empties you will only suck air into the system and have to start all over.



    What I did to prevent this is put a small tube with one of the mityback tips inserted into the hole in the bottom of the resivoir and the other end into a large bowl or container filled with fresh fluid instead of the mityvac in this picture.


    I used a screwdriver to tap the line while the system was under that psi vaccuum to loosen any stuck bubbles.



    And looky here what do we get.




    With this method you don't need to perform the final steps of the Buschman's because the system is under such high psi for such a long time it's very thorough. When you don't see any more bubbles you can disconnect the master and pull the line back down and plug it back in and your done.

    IF you have a brand new slave it would be a good idea to bleed it before you install in on the tranny so that you won't have to when you are under the car.



    Hope this helps. Ask questions if needed.

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