bleeder valve size on clutch hydraulics

I have to push my clutch pedal ALL the way to the floor and even then shifting is rough. It's been suggested I may have air in the hydraulics, so I want to try bleeding. A competent assistant may be a problem, so I want to install Speedbleeders (which I put on my brake cylinders, and love).

 

But I have no idea what size they need to be (master & slave) and neither the nice folks at Speedbleeder, nor my Subaru dealer, has any idea. SB did suggest that the diameter is probably 1mm smaller than the wrench size, so that could be a starting point. And they had a note that a later model WRX was 7mm (w/ 1mm thread pitch and 8mm wrench size), which mine also uses an 8mm wrench. So that's probably it, except they have a "short" and a regular length version. Anyone have any idea ? TIA !

Edited December 4, 2018 by RustyShackleford

You dont want to install speed bleeders. You might think you do now, but you dont. If there is air in the system now, it came from a leak. Find the leak.

 

If the fluid is boiled or full of water, speed bleeders are not the answer.

Thanks for the reply. Why would speedbleeders not help getting water or compromised fluid out ? How should I find the leak ? I'm not really losing fluid; but I guess it'd be air leaking in, not fluid leaking out. Can you detail for me how you'd suggest that I proceed ? Thanks.

How old is the fluid? Subarus bleed point is at the bottom, not the top. Its ass backwards. Dont mess with the bleeders.

Fluid is as old as the car, I believe; I change out the brake fluid every year or two, but never done the clutch. It looks like there's bleed valves on the master and slave cylinders both. I appreciate your responses, but I still am not sure what you're suggesting I do.

If you want to risk air locking the master you can bleed them. If you dont have a preesurized vessel (tool) you can use a friend to push the clutch. Otherwise you can recover the fluid from the master res (vacuum pump, or rags if u must) then refill. Pump the clutch a bunch and repeat.

 

You need to replace the fliid. Chances are the bleeders are siezed 12 years without movement.

 

It is not worth installing speed bleeders. Once the system is dry you will have a good time priming it again.

... A competent assistant may be a problem...

 

All you need is a sturdy piece of wood dowel, or plastic pipe, to place between the steering wheel and the clutch pedal (when it is down at the floor). This will pressurize the system so you can bleed it.

Although OP may have fixed the issue, I'll echo what others have said: replace the fluid first.

 

Even if you don't do a full bleed, replace it as m sprank noted, getting as much out as you can and refill. When I was having issues, I got as much out with a syringe as I could and refilled and just that first replacement was a marked improvement in clutch operation.

All you need is a sturdy piece of wood dowel, or plastic pipe, to place between the steering wheel and the clutch pedal (when it is down at the floor). This will pressurize the system so you can bleed it.

But it stops putting pressure on the clutch pedal as soon as you open the bleeder, doesn't it, so won't push the pedal all the way to the floor ?

 

When I was having issues, I got as much out with a syringe as I could and refilled and just that first replacement was a marked improvement in clutch operation.

Wow really, so without bleeding at all, just suctioning out the reservoir and re-filling it ?

 

I did do a bleed, just with the slave cylinder's bleeder and an assistant. When opening the bleeder, the pedal went straight to the floor and stayed there. Just moving it back and forth with my hand re-pressurized it; not exactly the behavior I was expecting. Did this about half-dozen times so flushed a good bit of new fluid thru there. I think it improved things a little but not much.

So, a new term to me: "Air Locking the Master". I assume it means trapping air downstream of the plunger that you are unable to remove from the bleed screw on the slave?

 

My 05 GT has a bleed screw on the master, this does not show in the manual. The instructions for bleed/replacement do not mention it either. The procedure for fluid change/bleed is pretty standard using only the slave bleed.

 

Can anyone give a step-by-step procedure for changing the fluid in the clutch taking into consideration the (2) bleed screws available to assure complete fluid change and not trapping any air in the system?

 

Thanks for any help you can give.

I'll give it a shot and see if you think this would be a correct procedure:

 

1. Remove fluid from the reservoir with a syringe.

2. Wipe out the reservoir with a lint free cloth to remove any dirt/debris.

3. Fill reservoir with fresh fluid.

4. Attach a hose to Master bleeder.

5. Have someone slowly press clutch pedal down then open bleed screw on Master then close after a few seconds and retract clutch pedal.

6. Repeat until clean fluid free of bubbles comes out.

7. Remove hose from Master and attach hose to Slave bleeder.

8. Have someone slowly press clutch pedal down then open bleed screw on Slave then close after a few seconds and retract clutch pedal.

9. Repeat until clean fluid free of bubbles comes out.

10. Torque bleed screws to 5.8 ft-lb

11. Check for leaks and road test.

 

Comments?

It might work. It should work. But I have had to bench bleed sooo many my fingers are crossed for you. Always a bit of trepedation when a Subie clutch res is dry. Finicky bunch.

Thanks for the reply.

 

I completed the fluid change. One observation was that when bleeding the clutch, the clutch pedal would almost drop to the floor even if you only depressed it half way, requiring pulling it up. Any idea why?

 

A related question: I had my clutch replaced some years ago and I noticed that the force required to push down the pedal was greatly reduced. After changing the clutch fluid the pedal became considerably harder. I remember having the same issue with the fluid change then (pedal dropping to the floor).

 

Any thoughts about what is happening here?

Common occurrance. Has to do with action of the cylinders, suction and air (as best I could figure). Spring return clutches seem to exhibit it more too. By depressing the pedal to the floor you are extending the piston beyond its normal point. Some say it could cause seal damage. If it bothers you, use a block of wood to limit travel of the pedal from hitting the floor.

 

New fluid can make the pedal feel stiffer. Especially if the old fluid had lost viscosity. Brake fluid is hydroscopic (absorbs moisture from air) and degrades with time.

Any thoughts about what is happening here?

 

 

The return spring is on the clutch fork, so when the system is bled the spring is always retracted (no pressure in the slave cylinder); thus you have to pull the pedal back because the spring exerts no pressure with the fork & slave already retracted.