Bleeding G50 slave

[Hendog]

I’ve bled my G50 slave before so it’s not new to me, but this time I have a problem. I started by bleeding all four corners of the brakes using my Motiv pressure bleeder. I only run 2-3 lbs of pressure to bleed the brakes and it all went well. I then went on to bleed the slave for the clutch. Nothing came out when I opened the bleeder, so I closed and added more pressure ~6 lbs then opened the bleeder and still nothing. I made sure the bleeder wasn’t plugged somehow (even though it was capped prior to working on it).

So here’s where things go sideways; I had not done this before. With the bleeder cracked open and about 6 lbs from the Motiv I pushed “gently” on the clutch pedal. It had zero resistance and seemed like it fell to the floor; that’s an exaggeration, it didn’t go all the way down but it sure went down easy, and it stayed there. I’ve read stories where pushing the clutch beyond it’s regular travel can damage the master cylinder, which is why I was very careful when I pushed in this one. It looks like some bit of fluid spit out of the bleeder but nothing much more than that. I closed the bleeder, and with my hand I checked the clutch pedal for feel. I can pull it up and push it back down to where it was. It doesn’t seem to be activating anything. At this point I added more pressure, up to 14 psi but no change at the bleeder and no change with the pedal, it’s still down.
Question: What causes the pedal to come back up in a normal situation?

The only reason I was bleeding the system is because it was over due: the last time was in 2015, 21K Km ago. Brakes and clutch were operating fine, but it was just time to get it done. I’m not sure where to go from here; any help would be greatly appreciated.

[yelcab1]

What caused the pedal to come back up under normal circumstances?

1. Pedal return spring
2. Pressure plate pushing back on the throw-out bearing which pushes back on the hydraulic fluid in the slave circuit, which pushes back the pedal.

You have air in the circuit and it needs to work its way out.

First of all, using the Motive system requires a totally leak proof circuit. Did you clamp shut the overflow tube at the master cylinder? Do that first.

Second, connect the motive bottle back up. Pump it to 10-15 psi. No more than 15 is ever needed.
Jack the rear end of the car up so you can get under the gear box, connect a hose to the bleeder valve, put the open end of the hose into a container with a bit of fluid so no air can get back into the hose while bleeding.
Crack open the valve, if no fluid is coming out, help it along by pumping the clutch pedal slowly.
Do this until clean fluid is coming out of the hose in a steady stream, shut the valve.

Test the pedal to see if you have clutch pressure. This should do it if you have not done anything to the clutch hardware.

[john walker's workshop]

Bleed it with the pedal all the way up.Tie it to the steering wheel if you have to. Never had to pump it. I just use air pressure in my Motiv unit.

[Hendog]

Originally Posted by yelcab1

What caused the pedal to come back up under normal circumstances?

1. Pedal return spring
2. Pressure plate pushing back on the throw-out bearing which pushes back on the hydraulic fluid in the slave circuit, which pushes back the pedal.

You have air in the circuit and it needs to work its way out.

First of all, using the Motive system requires a totally leak proof circuit. Did you clamp shut the overflow tube at the master cylinder? Do that first.
Yup, would not have been able to bleed brakes otherwise

Second, connect the motive bottle back up. Pump it to 10-15 psi. No more than 15 is ever needed.
Jack the rear end of the car up so you can get under the gear box,
Yep, it's on jack stands
connect a hose to the bleeder valve, put the open end of the hose into a container with a bit of fluid so no air can get back into the hose while bleeding.
Crack open the valve, if no fluid is coming out, help it along by pumping the clutch pedal slowly.
That's where my problems started
Do this until clean fluid is coming out of the hose in a steady stream, shut the valve.

Test the pedal to see if you have clutch pressure. This should do it if you have not done anything to the clutch hardware.

Originally Posted by john walker's workshop

Bleed it with the pedal all the way up.Tie it to the steering wheel if you have to. Never had to pump it. I just use air pressure in my Motiv unit.

Thanks John, I was hoping you would chime in. The pedal stays up, no problem, when I pull it up. I'll keep at it.

[Hendog]

A week later I'm finally getting back around to this...

Is this the line to my slave cylinder?

[Flat6pac]

The slave feed is higher on the reservoir then the brake feed and drops down to the pedal area with another slave on the clutch pedal
Bruce

[Hendog]

Confession: I had pinched the line to my slave. I removed it and then took the pic above. Once that pinch was removed I was able to bleed and restore my clutch action. I buttoned it all up and took it for drive: brake and clutch are great, transmission shifts nice as well (I changed the gear oil too).

This hassle was nothing more than a self inflicted "wound" Thank you all for your responses.

[Ctopher]

Man we all have had those! Glad you figured it out and now you know….and knowing is half the battle!

And now I know for when I do my flush here soon.



CTopher

Originally Posted by Hendog

This hassle was nothing more than a self inflicted "wound" Thank you all for your responses.

[Marine Blue]

Originally Posted by Hendog

Confession: I had pinched the line to my slave. I removed it and then took the pic above. Once that pinch was removed I was able to bleed and restore my clutch action. I buttoned it all up and took it for drive: brake and clutch are great, transmission shifts nice as well (I changed the gear oil too).

This hassle was nothing more than a self inflicted "wound" Thank you all for your responses.

If it makes you feel better I did the exact opposite when I bled mine. Basically underfilled the reservoir and pushed air into the entire line !

Once I realized the issue I filled the reservoir way up and purchased a vacuum bleeder to pull fluid through. Works beautifully now and on the plus side I know its completely flushed.

[Hnichols]

Originally Posted by Hendog

A week later I'm finally getting back around to this...

Is this the line to my slave cylinder?

It's a moot point now, but I'm surprised the vise-grips pinching your return line were adequate. When I tried that I had fluid leak out under the car and couldn't figure out what was wrong. I pinch it with a c-clamp.

[Locker537]

Instead of pinching the vent line, I pop it off and cap it with a silicon cap for that reason.

[Cloggie]

OK, just did mine and learned a lot.

Mine was a completely new system - lines, master, slave all completely empty.

I am a gravity bleeder kind of guy so did that first.....didn't work. Fluid came out of the slave, but no clutch action.

I got very frustrated and removed the slave from the transmission and bled while it was hanging - no avail.

Called it quits, consulted the bottom of a few glasses of whiskey and got at it again today.

Long and the short of it is that I failed to adjust the rod on the master cylinder side of things as shown below.



Shown is it set to its final length, originally it was completely unthreaded and the stop on the clutch pedal was actually on the floor.
What was happening is there was just not enough stroke on the master cylinder with the rod as loose as I had it, hence not fluid pump and hence no clutch actuation.

I believe that you can use that threaded rod to adjust the clutch pedal position - within limits of course - and now it is quite easy to get the brake and clutch pedals set to the same height, the way I like them.

To be fair, I have a completely adjustable throttle pedal so I can fiddle endlessly to get it all where I want it to be.

Anyway, redid the gravity bleeding and it is definitely a slow process, give it at least 10 minutes after first appearance of fluid on the slave cylinder bleed. I did cycle the clutch pedal several times and got my initial actuation.

I then followed John's advice and cycled the pedal with the slave bleed open which got things even tighter after a further gravity bleed.

I will probably let it set for a bit and rebleed when I install the engine (I just have a mockup in it now).

Hope this helps someone....and oh yes, keep that reservoir topped up, I actually went through more flushing fluid with the clutch than I did with gravity bleeding all four of my Turbo calipers which were also a completely new system with new everything.

D.