Clutch Fork movement & Master Cylinder

[dondel]

Hi all,

I had last week lost of pressure on the clutch; with some problems I managed it back home. Before I lost the pressure, I noticed problems to change the gears which became later on impossible.

I checked the 2 Cylinders, which seem fine to me. I didn't notice any leaking of the pipes. Unfortunately, I couldn't open the bleed screw; so I couldn't air the system. (After a lot of chemical and brute force, I managed to open the screw )

1st question: how do you open the Master Cylinder to check if the rubber is still fine? I read somewhere in the forum that a member changed the rubber in the master cylinder, but I don't see where to open it. I managed to take off the "ring" and the "washer" but the rest seems to stay in the cylinder.

2nd question: I was wondering how the cylinders interacts with the clutch. At the RHD side of the gearbox, you have this so called clutch fork which is moved by the slave cylinder. At least on my BJ8, this fork is moving "freely" in both directions; no "resistance" or so is keeping it in one position. As the slave cylinder (different to the master) is not connected as such to the push rod, it cannot be pulled back by the cylinder it self. So is this free movement ability of the clutch fork correct or is there something broken?

I hope I was any clear and would be very grateful for your thoughts!!

 

[bob hughes]

Ouch

This sounds very strange, I assume that the master cylinder has been removed from the car? Having removed the circlip ring the push rod can be removed, the insides should be able to be removed. Try blowing air through the hole at the other end keeping your thumb over the second hole, or, just tap the open end gently to entice the piston to come out.


How much movement do you have in the clutch fork end, you can expect some as a sort of waggle but there has to be very strong spring resistance as the arm moves back, you will not be able to produce the movement manually as the force required is large. This force is the one that also returns the slave cylinder push rod.

As an aside, I had to replace my master cylinder a few weeks ago as the re-rubbering kit did not work - I had the same gear change problems. If the slave cylinder has broken down, you should see fluid behind the dust cap, if the master cylinder is at fault, you may not detect leakage, I could not see any on mine, yet that was the cause of the problem.

You are going to have to release that bleed screw to bleed the system, you should be able to get enough access to it from inside the car, but if you are working from underneath, you may not. If it is really tight, consider removing the slave cylinder out of the car and work on it on a bench.

Best of luck

Bob

 

[Keoke]

Hi all,

I had last week lost of pressure on the clutch; with some problems I managed it back home. Before I lost the pressure, I noticed problems to change the gears which became later on impossible.

I checked the 2 Cylinders, which seem fine to me. I didn't notice any leaking of the pipes. Unfortunately, I couldn't open the bleed screw; so I couldn't air the system. (After a lot of chemical and brute force, I managed to open the screw )

1st question: how do you open the Master Cylinder to check if the rubber is still fine?

[A]
Remove the cylinder from the car carefully removing the pipes.

I read somewhere in the forum that a member changed the rubber in the master cylinder, but I don't see where to open it. I managed to take off the "ring" and the "washer" but the rest seems to stay in the cylinder.


Now that you have the "ring " and washer removed;

Tap the cylinder lightly on a piece of wood to jar the internal piston and rubbers out the same end as the ring came from. Kits are available from the stockist to rebuild the cylinder or it can be rebuilt by professionals or a replacement unit can be purchased from the stockist.

2nd question: I was wondering how the cylinders interacts with the clutch. At the RHD side of the gearbox, you have this so called clutch fork which is moved by the slave cylinder. At least on my BJ8, this fork is moving "freely" in both directions; no "resistance" or so is keeping it in one position. As the slave cylinder (different to the master) is not connected as such to the push rod, it cannot be pulled back by the cylinder it self. So is this free movement ability of the clutch fork correct or is there something broken?

[C[
It sounds like the Slave cylinder has failed. Consequently, you do not feel the resistive load of the clutches pressure plate.

I hope I was any clear and would be very grateful for your thoughts!!

----------------------------------- Keoke

 

[dondel]

Thanks Bob!

How much movement do you have in the clutch fork end, you can expect some as a sort of waggle but there has to be very strong spring resistance as the arm moves back, you will not be able to produce the movement manually as the force required is large. This force is the one that also returns the slave cylinder push rod.

Well, that's what I was afraid of... no resistance at all in my case! I can move the fork very easy in both directions. The slave cylinder would never be pushed back.
So this means that there is something broken in the clutch!?

Does anybody know how exactly the clutch fork is moved back towards the front? Is there a spring, I suppose, and where is that located... Sounds like I have to disassemble the whole car?

So I assume that is the problem why I got no pressure on the clutch pedal anymore and not because of the hydraulic system...

Just to add, I recently changed the oil in the gearbox. Could this have something to do with the problems? Perhaps the wrong oil?

 

[TimK]

The spring returning the clutch is the pressure plate which disengages the clutch when the clutch fork is pushed forward by hydraulic fluid then presses the throw out bearing (inside the bell housing) against the pressure plate releasing pressure on the clutch disk. If the throw out bearing is worn out there will be a lot of free play and it won't reach the pressure plate enough to disengage the clutch. If someone in the car depresses the clutch pedal, does the clutch slave pin push forward on the throw out bearing lever, also called the clutch fork (the one that goes into the bell housing to which the throw out bearing is attached).
See the Moss catalog section on clutch system.

If so the hydraulics may not be the problem. The throw out bearing can only be replaced by removing the transmission, which I have done three times in the last three years. I can walk you through it if you haven't done it before. If you do remove the transmission, you should replace the clutch and pressure plate along with the throw out bearing if it is old.

the throw out bearing presses down on the center of the pressure plate.
Your problem has nothing to do with changing the oil.
This photo shows the throw out bearing lever (clutch fork) attached to the clutch slave pin.

 

[bob hughes]

Hey Tim, can you remember how much free movement there should/could be on the fork end before you hit the true clutch resistance, I can't.

Always a good idea to check out the hydraulics before you pull the gear box out though, to see if the action is working.

If the gear box has to come out, think about re-newing the bearing in the end of the crank and if you feel that you are competant, add in an aftermarket oil seal to the crank - (if you leak oil through the rear journal and into the clutch area)

Bob

 

[TimK]

Bob, no I can't remember amount of clutch fork free play, but not a lot. Yes, I did add a BCS rear main lip seal. I did not renew the crank bushing/bearing.

I didn't know how to tell if it needed it or how to do it and I didnt think to ask. I agree the hydraulics should be checked out before removing the trans.

 

[Keoke]

Hey Tim, can you remember how much free movement there should/could be on the fork end before you hit the true clutch resistance, I can'

OH!!!- about 1/8" to 1/4" Max I would say

 

[bob hughes]

<span style="color: #FF0000">I didn't know how to tell if it needed it or how to do it and I didnt think to ask. I agree the hydraulics should be checked out before removing the trans.</span>

Tim, Just a point for when you are in there next, my local restorer / mechanic replaces the bush as a matter of course when he replaces clutches etc, mine was oval where it had been worn and fell out so it was a no-brainer. I guess that you would need to mic the bush and the end of the shaft from the gear box if you were just checking for wear. I am told that you have to bash it out by breaking it up, this sounds a bit harsh, I would consider drilling out the centre first to weaken the side walls then run a fine point down the side to buckle it

 

[Bob_Spidell]

Hardly worth it for a 'once-in-a-lifetime' job, but there are pullers available (you might be able to rent or borrow one from the local parts house):

https://www.amazon.com/Mountain-MTN9001-Pilot-Bearing-Puller/dp/B000X282DM


You can also 'chip' them out with a chisel, or possibly screw a big bolt inside that can be yanked on. Be careful not to gall the cavity in the flywheel, if it's damaged bad enough you could distort the new bushing. If there's enough drag on the gearbox input shaft it could affect shifting. Also, don't apply any more force than necessary on the new bush else you peen a lip on it.

Usually, the new bushing should be soaked in oil prior to installation.

 

[TimK]

Thanks for the advice on the pilot bearing. I doubt I am going in there again. I am 67 years old and put less than 500 miles a year on my car. It shifts fine and the bearing looked good to me (see photo above). But it is nice to know there are pullers for that job.

 

[dondel]

Sorry for my late answer; was (again abroad for work)
Well, 1st thanks already for all your information!

Hey Tim, can you remember how much free movement there should/could be on the fork end before you hit the true clutch resistance, I can'

OH!!!- about 1/8" to 1/4" Max I would say

Well, I have a free movement there of estimated 1"

The cylinders seem fine to me; they produce pressure when testing them (outside the car; without oil). When they were still in the car connected to the pipes and the recipient, the slave didn't move anymore... But this, I think was because the clutch didn't move the slave back again; the slave remained at it's maximal position. For this, I asked how it should behave normally. Anyway, I think I will see to get a rebuild kit for the cylinders; just in case.

But still I have this fork movement.

So it seems to me that I will have to get the transmission out...
For this, I think I need better equipment... How do you do this "operation"? What is the best equipment / tools for this work?
In the Workshops books I have this open-heart operation is described to some extend, but I, not being a mechanic (and newbie) feel like lagging of information.

The other thing is, as said by (nearly) all of you is the things to change once I got the transmission out. I loose some oil a little bit everywhere (which always creates problem in our mandatory official technical control) so I think this would be the best timing for sealing everything, so that I will never ever again lose any oil :lol: .

Further I have some minor issues when changing gears 3 -> 2 or 2 -> 3; that the changing goes a little harder than 3<->4.
But this I will check with you guys in an other post; next year or so :crazy:

Long post nothing said, big thanks to all of you!
I am looking forward to your suggestions and holding of my hand

 

[Keoke]

For this, I think I need better equipment... How do you do this "operation"? What is the best equipment / tools for this work?

Floor jack,Block of wood, Jack stands and a strong back.---Keoke-- :laugh:

 

[TimK]

Keoke captured the basics, for a little more info, see my new thread on Transmission Removal/Replacement.