Slave cylinder bleeding
Discussion
Hi Kids...I've installed a new clutch slave cylinder and ss hose. Upon bleeding the system, I'm still incountering some grinding, reverse mostly. Before resorting to the adjustment screw, should wifey keep pumping ( the clutch pedal) and bleeding the system? We've been through the proceedure about 4 or 5 times. Clutch pedal feels normal. Thanks for the imput.
Dave
90SE
Dave
90SE
Did you make sure that the Spring in the Master isn't Broken?
These Springs can break in half and the system will feel like it working properly, but because the Master's Piston is not operating over its full range, there won't be enough Hydraulic Fluid to Fully Activate the Slave.
...replaced 2 of these Little Buggers, so far!
>> Edited by deecee on Tuesday 4th April 15:39
These Springs can break in half and the system will feel like it working properly, but because the Master's Piston is not operating over its full range, there won't be enough Hydraulic Fluid to Fully Activate the Slave.
...replaced 2 of these Little Buggers, so far!
>> Edited by deecee on Tuesday 4th April 15:39
My slave cylinder was the first to go, but the master went soon after and probably should be been done with the slave. So I would double check the condition of it. Bleeding the slave cylinder can be tricky. The best way to do it is to let it hang from the clutch line and then use a pressure bleeder to push the brake fluid through the system.
I agree with DK; however, if you don't have that system handy here's another trick. I still had the red hose when I replace the master cylinder. Bleeding was a pain but I could see the bubbles and notice that they were located just outside the slave cylinder. I worked the slave cylinder by hand until the bubbles were one big bubble. Then had my wife stomp on the clutch as I opened the bleeder valve. I could actually hear the bloop of air exit. I locked down the bleeder valve and all was fine. Rather than driving it on the road to check for grinding, we started the car while it was still on jack stands. Prior to bleeding, the wheels would turn even with the clutch fully depressed, after bleeding no wheel movement.
There are high points in the clutch hydraulic line where bubbles can collect. To get all the bubbles out, it's necessary to establish a continuous fluid flow that will carry the bubbles with it. Pumping the pedal is an intermittant process that has the fluid moving in spurts... starting and stopping. Move a bubble a little bit out of a high point and it just flows back up when the fluid stops while you're returning the pedal for the next stroke. You can Yo-Yo all day long and not get anywhere.
The best way to bleed the Esprit's clutch line is with a pressure bleeder. That will establish a continuous fluid flow that will carry any bubbles through and out of the system.
If you use a Gunson EZ-Bleed, then do not follow the instructions with regards to the pressure source. They suggest using the spare tire for a pressure source, but they don't tell you to let most of the air pressure out first. (!) Full tire pressure is way too much and will blow the cap off the reservoir... and brake fluid all over the place. Since brake fluid is very good at removing paint, that's not a good thing.
2.5 to 5 psi is all that's required. So I bought a small, 2-quart garden sprayer for US$10.00. The spigot/ ferrule on top of the sprayer where the wand/ nozzle would normally go is the perfect size to accept the air pressure tubing from the EZ-Bleed. Set it all up per the instructions minus the tire, give the sprayer's air pump a few strokes to lightly pressurize the system, then open the bleed screw on the slave cylinder and let it flow.
The only things you have to watch are:
1) The fluid flow through the clear tubing... keep it moving. If it stops, the air bubbles will start rising again. Give the sprayer air pump a couple of strokes as necessary to maintain the flow.
2) The fluid level in the EZ-Bleed's clear reservoir. If you run it dry and start pumping air into the clutch hydraulic system, you'll have to start all over.
When you're all done, the sprayer reservoir is also a convenient storage place for the EZ-Bleed bits.
Without a pressure bleeder, there are still some things you can do to make pedal pumping more effective.
First, bench bleed any new cylinders... master or slave. Get as much air out as possible before you begin the installation. The master can be messy since the outlet port doesn't have a valve like the slave's bleed screw. Hold it the wrong way and it will pee all over the place. A new master will usually come with a bolt or plastic cap plugging the port. Re-installing that after bench bleeding will minimize any mess. Have rags handy.
When you install the slave, make sure the bleeder screw is on top where the air bubbles will collect. It may be more convenient to reach when it's on the bottom, but it won't work well when it's not were the bubbles are going to collect.
The hydraulic line's route under the chassis backbone is the low point. From there it goes up to the slave and up to the master. Bleeding can be facilitated if any trapped air is given a one-way up-hill path and a little time to follow it.
Connect the slave to the hose, then allow it to dangle below the car with the bleeder open and pointing up. Then jack up the front of the car to establish an up continuously uphill path.
Fill the reservoir and do a quick bleed to fill the drained hydraulic line as much as possible. Then just let the whole thing sit for a while. Walk away and take a break. Over night is great.
In time, the zillion tiny bubbles in the fluid will join into a few large bubbles and migrate uphill to the master. In the stock system, there's a metal bundy pipe that goes upward from the master outlet, does a U-turn and heads back down. That U-turn is an air-trap and the most difficult place in the system to bleed. It's the cause of most of the Yo-Yo bleeding problems, and it's where the air in the system should have not collected if you left it alone for a while as noted above. So how do you get the air out?
First, go back to the slave that you bench bled before installing, and that's been dangling at the low point for a while, burping air. It should now be full of fluid with virtually no air. Push in on the spring loaded piston until it bottoms out, forcing all the fluid into the line. Do it with some force so that the bubble in the U-turn at the master gets pushed all the way through into the reservior. Push the piston in and hold it.
CAUTION: If the master reservoir is full when you push in on the slave piston, it will overflow. Remove any fluid from the reservoir first.
Push in the slave piston and hold it while an assistant tops off the reservoir. When you release the spring loaded slave piston, it should draw fluid back into the line at the reservoir... not air.
Repeat until no air is observed belching into the bottom of the reservoir when the slave piston is depressed. Then complete the slave/ pushrod/ adjuster screw installation. The system should be pretty free of air at that point and require minimal additional bleeding.
You can optimize your chances of success in that procedure if you gently reform the U-turn portion of the bundy pipe to minimize it's height and volume above the master cylinder's outlet port.
Personally, I don't understand that set up. The verticle U-turn is a natural air trap and just begs for bleeding problems. It seems like a 90 degree elbow fitting with little of no height above the outlet port would greatly simplify the bleeding process. Some of the aftermarket AeroQuip-style hose kits do eliminate that loop.
If the system is all together and you're just trying to do a little maintenance bleeding to cure a soft pedal, attack the U-turn at the master first. Over time virtually all air in the system will have collected there anyway so burping it may be all that's needed.
The simplest way is to depress the clutch pedal hard to the floor and hold it there for 15 seconds or so. Then snap-release it. Flooring the pedal will put as much fluid into the system as the cylinder can. Holding the pedal for 15 sec will allow any bubbles that were displaced downstream by the fluid to work their way back up to the top. Snap-releasing the pedal will carry the bubbles out to the reservoir with the returning fluid.
Have an assistant work the pedal while you watch the reservoir. If there is air in the U-turn, you will see bubbles burp into the reservoir when the pedal is released. If so, repeat the process until no bubbles appear.
BTW, if you ever allow the reservoir to go dry and pump air into the system (shame on you), the air can usually be burped out using that method without doing a full bleed. It won't fix a slave or master that's gone bad, but if the problem is just a little air it can be the quick roadside fix.
Air moves uphill through a liquid, so think about what's going on and be smarter than air.
;-)
Regards,
Tim Engel
The best way to bleed the Esprit's clutch line is with a pressure bleeder. That will establish a continuous fluid flow that will carry any bubbles through and out of the system.
If you use a Gunson EZ-Bleed, then do not follow the instructions with regards to the pressure source. They suggest using the spare tire for a pressure source, but they don't tell you to let most of the air pressure out first. (!) Full tire pressure is way too much and will blow the cap off the reservoir... and brake fluid all over the place. Since brake fluid is very good at removing paint, that's not a good thing.
2.5 to 5 psi is all that's required. So I bought a small, 2-quart garden sprayer for US$10.00. The spigot/ ferrule on top of the sprayer where the wand/ nozzle would normally go is the perfect size to accept the air pressure tubing from the EZ-Bleed. Set it all up per the instructions minus the tire, give the sprayer's air pump a few strokes to lightly pressurize the system, then open the bleed screw on the slave cylinder and let it flow.
The only things you have to watch are:
1) The fluid flow through the clear tubing... keep it moving. If it stops, the air bubbles will start rising again. Give the sprayer air pump a couple of strokes as necessary to maintain the flow.
2) The fluid level in the EZ-Bleed's clear reservoir. If you run it dry and start pumping air into the clutch hydraulic system, you'll have to start all over.
When you're all done, the sprayer reservoir is also a convenient storage place for the EZ-Bleed bits.
Without a pressure bleeder, there are still some things you can do to make pedal pumping more effective.
First, bench bleed any new cylinders... master or slave. Get as much air out as possible before you begin the installation. The master can be messy since the outlet port doesn't have a valve like the slave's bleed screw. Hold it the wrong way and it will pee all over the place. A new master will usually come with a bolt or plastic cap plugging the port. Re-installing that after bench bleeding will minimize any mess. Have rags handy.
When you install the slave, make sure the bleeder screw is on top where the air bubbles will collect. It may be more convenient to reach when it's on the bottom, but it won't work well when it's not were the bubbles are going to collect.
The hydraulic line's route under the chassis backbone is the low point. From there it goes up to the slave and up to the master. Bleeding can be facilitated if any trapped air is given a one-way up-hill path and a little time to follow it.
Connect the slave to the hose, then allow it to dangle below the car with the bleeder open and pointing up. Then jack up the front of the car to establish an up continuously uphill path.
Fill the reservoir and do a quick bleed to fill the drained hydraulic line as much as possible. Then just let the whole thing sit for a while. Walk away and take a break. Over night is great.
In time, the zillion tiny bubbles in the fluid will join into a few large bubbles and migrate uphill to the master. In the stock system, there's a metal bundy pipe that goes upward from the master outlet, does a U-turn and heads back down. That U-turn is an air-trap and the most difficult place in the system to bleed. It's the cause of most of the Yo-Yo bleeding problems, and it's where the air in the system should have not collected if you left it alone for a while as noted above. So how do you get the air out?
First, go back to the slave that you bench bled before installing, and that's been dangling at the low point for a while, burping air. It should now be full of fluid with virtually no air. Push in on the spring loaded piston until it bottoms out, forcing all the fluid into the line. Do it with some force so that the bubble in the U-turn at the master gets pushed all the way through into the reservior. Push the piston in and hold it.
CAUTION: If the master reservoir is full when you push in on the slave piston, it will overflow. Remove any fluid from the reservoir first.
Push in the slave piston and hold it while an assistant tops off the reservoir. When you release the spring loaded slave piston, it should draw fluid back into the line at the reservoir... not air.
Repeat until no air is observed belching into the bottom of the reservoir when the slave piston is depressed. Then complete the slave/ pushrod/ adjuster screw installation. The system should be pretty free of air at that point and require minimal additional bleeding.
You can optimize your chances of success in that procedure if you gently reform the U-turn portion of the bundy pipe to minimize it's height and volume above the master cylinder's outlet port.
Personally, I don't understand that set up. The verticle U-turn is a natural air trap and just begs for bleeding problems. It seems like a 90 degree elbow fitting with little of no height above the outlet port would greatly simplify the bleeding process. Some of the aftermarket AeroQuip-style hose kits do eliminate that loop.
If the system is all together and you're just trying to do a little maintenance bleeding to cure a soft pedal, attack the U-turn at the master first. Over time virtually all air in the system will have collected there anyway so burping it may be all that's needed.
The simplest way is to depress the clutch pedal hard to the floor and hold it there for 15 seconds or so. Then snap-release it. Flooring the pedal will put as much fluid into the system as the cylinder can. Holding the pedal for 15 sec will allow any bubbles that were displaced downstream by the fluid to work their way back up to the top. Snap-releasing the pedal will carry the bubbles out to the reservoir with the returning fluid.
Have an assistant work the pedal while you watch the reservoir. If there is air in the U-turn, you will see bubbles burp into the reservoir when the pedal is released. If so, repeat the process until no bubbles appear.
BTW, if you ever allow the reservoir to go dry and pump air into the system (shame on you), the air can usually be burped out using that method without doing a full bleed. It won't fix a slave or master that's gone bad, but if the problem is just a little air it can be the quick roadside fix.
Air moves uphill through a liquid, so think about what's going on and be smarter than air.
;-)
Regards,
Tim Engel
I know this is probably not much help, but I recently replaced both the slave cylinder and red hose at the same time on my 89NA, so I thought you might be interested in my experiences. Basically - I followed the guide on www.andywhittaker.com, and encountered no problems, which makes me suspect that something other than simple bleeding technique could be your problem.
For the record, I fitted the new line and cylinder, filled the master cylinder (without priming the slave, dangling it upside down or any cunning trickery like that), had my girlfriend pump the clutch pedal a few times then push it to the floor while at the same time I released the bleed nipple. I repeated these last two steps a dozen times and all was good. A rare instance of things going right for me
The only thing that I did that was notable ormay have assisted things was that I had the car reversed up onto a ret of 30cm high ramps...so I guess the slave was elevated slightly higher than normal relative to the master. This may have helped bubbles rise up towards the slave.
Incidentally - fitting a new slave + SS clutch line (plus replacing the rubber bushes where the gear lever joins to the cables under the centre armrest) made an incredible difference to my gearchange. Trust me - your efforts will be rewarded, eventually!
Cheers, Si
For the record, I fitted the new line and cylinder, filled the master cylinder (without priming the slave, dangling it upside down or any cunning trickery like that), had my girlfriend pump the clutch pedal a few times then push it to the floor while at the same time I released the bleed nipple. I repeated these last two steps a dozen times and all was good. A rare instance of things going right for me
The only thing that I did that was notable ormay have assisted things was that I had the car reversed up onto a ret of 30cm high ramps...so I guess the slave was elevated slightly higher than normal relative to the master. This may have helped bubbles rise up towards the slave.
Incidentally - fitting a new slave + SS clutch line (plus replacing the rubber bushes where the gear lever joins to the cables under the centre armrest) made an incredible difference to my gearchange. Trust me - your efforts will be rewarded, eventually!
Cheers, Si
lotus still stands by the use of the red hose, and does not consider it a design flaw. while i am not a fan of lotus policies, i have not yet found a need to do the upgrade. my fear is that the better hoses will cause leaks at all the weak points in the system. meanwhile, it shifts reasonably well compared to some of the inappropriate race clutches they plunk into ferrari streetcars.
Simon..Short of borrowing your girlfriend ( lots of jokes come to mind) I'll get wifey to run the clutch pedal again. We only bleed it 3 times. I'm assuming we have alot more bleeding to do to expel all the air. If that doesn't work, I'll move on to Tims proceedures. Thanks
Dave
90SE
Dave
90SE
Another method is to use a hand held vacuum pump with a brake bleeding kit. You will then be sucking the fluid from at the slave. This method proved pretty effective with my 300ZX Twin Turbo, which have difficult to bleed clutch systems. The vacuum pump(many makes) and bleeding kit(made by Lisle) can be had at Sears....Mityvac also has one. Using this makes it a one person job too...you just need to keep your eye on the fluid level to make sure you don't suck it dry.
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