Reverse Bleeding the Slave Cylinder
06-23-2018, 03:30 PM
#1
Burning Brakes
Thread Starter
Reverse Bleeding the Slave Cylinder
In the course of replacing the timing belt (and several other things) on my 1987 928 S4, I had to remove the slave cylinder in order to insert the flywheel lock. Since the car has the original hard lines, I found it easiest to disconnect the hydraulic line at the slave cylinder, which necessitated bleeding the slave cylinder when I put everything back together.
Thanks to posts by others on this forum, I found the most effective method to be to "reverse" bleed the system. Using the following:
https://www.ebay.com/itm/Portable-Pn...t/201872823256
I used the bleed valve hose that comes with the kit, and jammed the cut end into the steel orifice of one of the master cylinder adapter caps that it comes with, from the inside. Then hooked up the cap to the tank and otherwise used it as instructed. I set the pressure for roughly 25psi. Before beginning, I made sure that the clutch pedal was all the way out, removed the brake fluid reservoir cap, and then opened the bleed valve on the slave cylinder to let fluid drain out until the reservoir was almost empty. Then I put the bleed kit's bleed valve adapter onto the slave cylinder's bleed valve, and opened the ball valve on the kit's hose. I could hear the air gurgle into the reservoir after a short while. I turned off the ball valve when the reservoir was at the maximum level mark, tightened up the bleed valve, closed the reservoir, and checked the pedal. Perfect. One shot, and it's done.
I'm posting this to confirm that this method and particular kit works. You can find these under lots of names in lots of places, so it's not just this one kit that would work.
One thing to note is that the tank needs to have a significant amount of fluid in it to work. Otherwise, the bladder will seal against the outlet inside of the tank. I put in almost a quart after a cup or two wasn't enough. The downside is that it looks to be a real pain to switch out the brake fluid for a different kind if you need to use it on different vehicles.
It took a little bit to setup, but compared to any other method of bleeding, this was a snap.
Thanks to posts by others on this forum, I found the most effective method to be to "reverse" bleed the system. Using the following:
https://www.ebay.com/itm/Portable-Pn...t/201872823256
I used the bleed valve hose that comes with the kit, and jammed the cut end into the steel orifice of one of the master cylinder adapter caps that it comes with, from the inside. Then hooked up the cap to the tank and otherwise used it as instructed. I set the pressure for roughly 25psi. Before beginning, I made sure that the clutch pedal was all the way out, removed the brake fluid reservoir cap, and then opened the bleed valve on the slave cylinder to let fluid drain out until the reservoir was almost empty. Then I put the bleed kit's bleed valve adapter onto the slave cylinder's bleed valve, and opened the ball valve on the kit's hose. I could hear the air gurgle into the reservoir after a short while. I turned off the ball valve when the reservoir was at the maximum level mark, tightened up the bleed valve, closed the reservoir, and checked the pedal. Perfect. One shot, and it's done.
I'm posting this to confirm that this method and particular kit works. You can find these under lots of names in lots of places, so it's not just this one kit that would work.
One thing to note is that the tank needs to have a significant amount of fluid in it to work. Otherwise, the bladder will seal against the outlet inside of the tank. I put in almost a quart after a cup or two wasn't enough. The downside is that it looks to be a real pain to switch out the brake fluid for a different kind if you need to use it on different vehicles.
It took a little bit to setup, but compared to any other method of bleeding, this was a snap.
06-23-2018, 05:02 PM
#2
Race Car
Nice job on the reverse bleed.
Just so you know, it is possible to remove the slave cylinder without detaching the line.
Just so you know, it is possible to remove the slave cylinder without detaching the line.
06-23-2018, 05:57 PM
#3
Former Sponsor
When I built my first one piece hose that replaces the stock rubber hose and the steel line under the starter, I did this only because I didn't have room for the steel line with a pan spacer.
This one piece hose has become one of our best sellers!
This hose allows simple removal of the clutch slave....allows the slave to be pulled straight out.
And reverse bleeding, because the slave can be lowered way down with the one piece hose turns a difficult task into a simple one.
Why Porsche didn't figure this out, is beyond me, although it is pretty obvious none of the engineers ever had to remove a slave cylinder.
This one piece hose has become one of our best sellers!
This hose allows simple removal of the clutch slave....allows the slave to be pulled straight out.
And reverse bleeding, because the slave can be lowered way down with the one piece hose turns a difficult task into a simple one.
Why Porsche didn't figure this out, is beyond me, although it is pretty obvious none of the engineers ever had to remove a slave cylinder.
06-23-2018, 07:27 PM
#4
Rennlist Member
When I built my first one piece hose that replaces the stock rubber hose and the steel line under the starter, I did this only because I didn't have room for the steel line with a pan spacer.
This one piece hose has become one of our best sellers!
This hose allows simple removal of the clutch slave....allows the slave to be pulled straight out.
And reverse bleeding, because the slave can be lowered way down with the one piece hose turns a difficult task into a simple one.
Why Porsche didn't figure this out, is beyond me, although it is pretty obvious none of the engineers ever had to remove a slave cylinder.
This one piece hose has become one of our best sellers!
This hose allows simple removal of the clutch slave....allows the slave to be pulled straight out.
And reverse bleeding, because the slave can be lowered way down with the one piece hose turns a difficult task into a simple one.
Why Porsche didn't figure this out, is beyond me, although it is pretty obvious none of the engineers ever had to remove a slave cylinder.
06-23-2018, 07:56 PM
#5
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Way back just after we went from wooden spoke wheels and Flintstone brakes, I remember having to invest in a bladder-style bleeder to replace the air-over-fluid style commonly used. Since then we've seen the Motiv and my similar but home-brew garden-sprayer versions move into popular use. This kit, with the assortment of adapters and hoses on top of the bladder-style tank, is an absolute bargain.
It won't solve some of the common issues that Greg's hose cures, like reverse-bleeding with the slave low so the bubbles can flow uphill to the reservoir. For those of us with multiple vehicles to maintain, not all of them blessed with the same ATE reservoir cap, the combination of things makes a pretty elegant solution.
It won't solve some of the common issues that Greg's hose cures, like reverse-bleeding with the slave low so the bubbles can flow uphill to the reservoir. For those of us with multiple vehicles to maintain, not all of them blessed with the same ATE reservoir cap, the combination of things makes a pretty elegant solution.
06-23-2018, 09:49 PM
#6
Burning Brakes
Thread Starter
In order to leave the slave cylinder connected, I would have had to remove the starter, or at least loosen it. But, the slave cylinder was leaking. So, it was a good opportunity to rebuild it.
Greg, I would like to get one of your hoses. Is it best to contact you through your site to order it, or...? Does your site list all of the available products? If there are other things that I can use, I'll probably just order it all at once.
Greg, I would like to get one of your hoses. Is it best to contact you through your site to order it, or...? Does your site list all of the available products? If there are other things that I can use, I'll probably just order it all at once.
