Slave Cylinder Help Please

[2000RangerY]

I am in a pickle. I am working on my daily driver...

I just rebuilt the transmission. In the process I replaced the rear main seal, clutch and pressure plate, and slave cylinder.

The slave cylinder is not engaging. It only moves about 1/8. It seems weak? The new slave cylinder is much lighter and seems to have more plastic parts.

I have bled it and I have a solid stream of new fluid. No bubbles or air coming out. The system didn't bleed down of fluid either.

Before I buy another slave cylinder, is it possible that I installed something wrong? Nothing comes to mind. Only 2 bolts holding on the slave cylinder.

Thank you for your help.

P

 

[RonD]

Open bleeder on slave and let it gravity bleed for 20 seconds or so, tighten bleeder
Then check reservoir, remove the rubber cup in reservoir(air dam), top up fluid as needed, leave cup out for now
Air dam limits air contact with fluid, so not part of the system working or not

Now watch inside reservoir while someone pushes clutch pedal down
You should see NO FLUID come up into reservoir, if it does replace master

Clutch pedal has bushings at the top pivot point, can cause less pedal travel, so less fluid flow into slave
Should "feel" funny when pushing down the pedal

Master itself is at an angle, this means it can get air trapped at the top, by pushrod
Need to pull out the master and turn it "up" to bleed out the air

 

[2000RangerY]

Open bleeder on slave and let it gravity bleed for 20 seconds or so, tighten bleeder
Then check reservoir, remove the rubber cup in reservoir(air dam), top up fluid as needed, leave cup out for now
Air dam limits air contact with fluid, so not part of the system working or not

Now watch inside reservoir while someone pushes clutch pedal down
You should see NO FLUID come up into reservoir, if it does replace master

Clutch pedal has bushings at the top pivot point, can cause less pedal travel, so less fluid flow into slave
Should "feel" funny when pushing down the pedal

Master itself is at an angle, this means it can get air trapped at the top, by pushrod
Need to pull out the master and turn it "up" to bleed out the air

Thank you for your help. I will try that tomorrow for sure!

Just to make sure we are on the same page about the master... I didn't let the fluid run out during the process. All of the air should have been limited to the slave cylinder. I am not sure how air would have gotten to the master. Also, I do have full travel of the clutch pedal. The pedal only seems "normal" at the very end of the travel. About 1/4 of pedal and the slave cylinder only moves about 1/8 inch.

Thanks again.

 

[RonD]

There are only light springs in master and slave, the Return spring for the pedal is the pressure plate springs/fingers
When you install the transmission the slave's throwout bearing should contact the "fingers" once bellhousing is touching engine, so 0 clearance, its recommended to open slave bleeder when install trans because of the 0 clearance, but you don't have to

When you press clutch pedal down you should immediately feel the "finger spring" resistance
At top of pedal movement
What you describe is no resistance until pedal is down most of the way
Slave travel is about 1/2"

So either slave/throwout bearing is not touching the pressure plate springs, or fluid flow is not starting until pedal is most of the way down

Hydraulics are pretty simple to understand
You have 2 chambers with a hose in between
If you push/force fluid out of one chamber then that amount of fluid goes to the other chamber

The piston in the master pushes fluid out as you press down the clutch pedal
That fluid flows down the hose and into the slave
The slaves chamber must expand to take on the extra fluid, but has resistance of the "finger springs" to overcome
Thats the resistance you should feel in the pedal as slave tries to expand

If there is no resistance then fluid is not flowing, or is leaking out

A "bad slave" is when it leaks
I don't think you can get "the wrong" slave that would bolt to bellhousing
I guess you could leave off the throwout bearing, it does come off, but new slave would come with it attached

Master piston could have a bad seal so some fluid is pushed up into reservoir
Or into top of master, but it should leak out in the cab if that was happening

If you disconnect the hose from the slave, hoses valve will close
Then try to push down clutch pedal
Should be hard as a rock no movement at all
This would mean master is not leaking fluid and air free
If you can push it down a bit or slowly then replace master

 

[2000RangerY]

There are only light springs in master and slave, the Return spring for the pedal is the pressure plate springs/fingers
When you install the transmission the slave's throwout bearing should contact the "fingers" once bellhousing is touching engine, so 0 clearance, its recommended to open slave bleeder when install trans because of the 0 clearance, but you don't have to

When you press clutch pedal down you should immediately feel the "finger spring" resistance
At top of pedal movement
What you describe is no resistance until pedal is down most of the way
Slave travel is about 1/2"

So either slave/throwout bearing is not touching the pressure plate springs, or fluid flow is not starting until pedal is most of the way down

Hydraulics are pretty simple to understand
You have 2 chambers with a hose in between
If you push/force fluid out of one chamber then that amount of fluid goes to the other chamber

The piston in the master pushes fluid out as you press down the clutch pedal
That fluid flows down the hose and into the slave
The slaves chamber must expand to take on the extra fluid, but has resistance of the "finger springs" to overcome
Thats the resistance you should feel in the pedal as slave tries to expand

If there is no resistance then fluid is not flowing, or is leaking out

A "bad slave" is when it leaks
I don't think you can get "the wrong" slave that would bolt to bellhousing
I guess you could leave off the throwout bearing, it does come off, but new slave would come with it attached

Master piston could have a bad seal so some fluid is pushed up into reservoir
Or into top of master, but it should leak out in the cab if that was happening

Thank you for the help. You are right, the pedal goes straight to the floor. There are no leaks and the bearing is touching the fingers. I am going to try bleeding it again tomorrow. I am going to test the system to the quick disconnect first. Once I have pressure, I will reconnect the slave and go from there.

I appreciate everyone help!

 

[RonD]

With quick disconnect off(hose off) clutch pedal should be rock hard, instantly

 

[2000RangerY]

Solved: I did a bench bleed of the master cylinder. It was amazing how much air got in it. After a while I decided to replace it with a new one due to the gunk coming out.

Next, I gravity bled the system back on the truck with the slave cylinder connected.

Thank you all for your help.
Merry Christmas.

 

[RonD]

Good work

And thanks for the update, it WILL help someone else down the road

Merry Christmas