belgiumbarry

i'm confused.... installed new MC and slave on my '82 clutch but doesn't work.
I pressure bleed from above , from under , i pushed the rod in of the slave etc.... nothing works.
Pedal has no resistance , pumping doesn't help making "any" pressure.

I assume in the MC , the plunger has a one way valve at the top ? if that one doesn't close , i just pump oil back to the reservoir ?

Are there other idea's/tricks to try ?

I already installed booster and new MC brakes…. if bad clutch MC i can start all over ….

Mrmerlin

best thing to do is install the Greg Brown flex hose to the slave then the bleed sequence takes about 4 mins to complete
LMK when you have this hose installed and I will write you a bleed procedure

belgiumbarry

Stan , i have the oem line with a just bought new flex hose….i assume bleeding "must" work with those too as in 99 % of 928's....
My pressure bleeder at 1.2 bar pumps fast oil from above down or from down to above , so sure no obstructions in the lines.

I'm more concerned in the new master.... pedal pumping it doesn't make any extra pressure…..

captainOCD

I also was finding it impossible to bleed the clutch with my pressure bleeder. I don't remember the exact sequence of what I did after trying the pressure bleed, but some combination of pumping the pedal, then going under, unbolting the slave, then with it angled with the cylinder pushing it all the way in, holding it for 30 sec or so, then letting it all the way out. After that a couple times I had a good pedal.

SwayBar

Instead of pushing the rod of the slave, unscrew the bolts on the slave almost all the way out, and pump the slave cylinder in and out until it feels very firm. This will pump the air naturally upwards-and-out thru the lines.

belgiumbarry

thanks Matt , seems i'm not alone.
I will try it that way , unbolt slave and push in the rod and hold it for 30 sec , several times…i did it only once.

will come back with results….

belgiumbarry

Thanks Swaybar , i can start with that trick.... and see what it gives.

belgiumbarry

tried it already and doesn't change anything…. no pedal.

GregBBRD

If the pushrod from the pedal puts any preload on the master, the port that allows fluid to go into the master will be blocked and you will not be able to bleed.

If you replaced the hose from the fluid reservoir to the master, making that hose too long and routing it incorrectly is an extremely common problem. An air bubble will be trapped in the low section and you can never bleed the system. The hose must run continuously downhill, without "dipping" below the level of the master cylinder. The hose must go around the power brake booster at the "3 o'clock" position (viewed from the front), for this to work.

I made my one piece hose to replace the rubber hose from the sway bar mount and the metal line under the starter to make pan spacers, high output starters, etc. easier to fit. Stan "figured out" that his hose makes the bleeding procedure much easier, which I ignored, for years. Then one day, after struggling bleeding a clutch for hours, I tried his method.

I'm not sure I will ever use the stock hose and line ever again...turns a miserable, long, tricky job into a five minute affair.

Instead of calling it "Greg's clutch hose", we really need to rename it to "Stan's clutch hose".

belgiumbarry

thanks Greg , much appreciated !

i tried it already today with pushrod preload and without , pedal up or down … no difference , was looking too at the old one if it could be blocked at a certain position ( seal just under the opening )

I can imagine one long hose is so much more simple instead of that short hose and hard line. But what is it's content ? If i push the slave all way in , oil ( and air ) must have pasted many times that little diameter length ...slave is diameter 24 mm , stroke about 30 mm … that's a lot of oil for such a tiny tube.

And yes, i renewed the hose master-reservoir.....and made it perhaps too "long" ….. will check it ! just don't understand the "3 o'clock" position (viewed from the front) ? the reservoir nipple is at 9 o'clock viewed from the front , no ? ( '82 928 )

Bulvot

If you have a pressure bleeder, I recommend reverse bleeding the slave cylinder. It works very well. I tried lots of methods recommended on here by people like Stan, but the only one that was simple, fast and never failed is reverse bleeding. The "hardest" part is knowing when to stop, so it helps to either have someone watching the reservoir, or running it slow enough that you have time to go back and forth and check.

The flex line is a very nice upgrade, but it's not at all necessary to bleed the system of air.

belgiumbarry

Thanks Bulvot , but i you mean by reverse bleeding is putting the pressure bleeder on the slave and push oil up … i tried that already many times. Oil is free running up ( i have the bleeder cap on the reservoir with a hose in a container … so no hurry , i can let it flow till pressure bleeder would be empty.

As Greg's tip... i tried it : pressure bleeder on slave , pushing oil up . Playing with the hose master-reservoir to have no air pockets …. no better , no pedal.

What i do not understand is that i get no pedal pressure with pumping , even if it would be a sponge one , but a bit of "working" …. ???

captainOCD

Sorry if it's obvious, but have you checked that the reservoir is completely topped off? I can tell you from experience (reservoir to master hose leaked) on my car that once the brake fluid level is below about 1/2 to 1/3 the reservoir is chambered such that no more fluid gets to the port for the hose. I remember going through hell with my brother on his e46 trying to bleed the clutch after an engine swap, and after a couple hours of frustration we realized that the chamber for the clutch in that car only filled from the rest when it was nearly topped off. Sometimes you get lucky with simple solutions.

belgiumbarry

thanks Matt for the idea , but reservoir is topped off, i'm aware of the chambers inside. A leaking clutch system will give you at least still brakes.
More, with the cap on the side , i cannot get a hose in it to suck it empty , for removal for example , so i drain it via the clutch slave and callipers ….

Last attempt i did see that with pedal pushed in , the pressure bleeder doesn't get oil from slave to above : so in that case the one way valve in the plunger is working . If i release the pedal , the flow is back.
This gives me the idea that , as long as there is air in the system , the pressure on the valve is not enough to close it by pumping the pedal. In this case we pump oil in the MC from the front chamber to the back chamber which is open to reservoir. Seems 1.2 bar from the bleeder closes it , so only pumping the pedal doesn't even make 1.2 bar in the front chamber…. just a guess….
Could be the reason why so many have troubles to bleed the system.
With pedal pushed in i have indeed a little bit of oil pressure at the slave , about 2" hose length oil when bleed nipple opened.

Mrmerlin

Ok with Gregs Hose installed
open the bleeder to the slave,
let it drip till the air looks to be out.

Remove the slave from the bellhousing.
Hold the bleeder port up and open it again this should get any air out of the slave.
then let it hang with the pushrod pointing to the floor.

Push the rod into the slave to full compression.
Hold this position for about 30 seconds.

Let the rod go , the spring will push the rod all the way out.

repeat this 3 times.
then install the slave,
NOTE use some fresh grease on the rod socket in the arm.
Press the clutch pedal it should be perfect.