Clutch fork free play on BJ8 How Much?

[jjs64bj8]

Just installed rebuilt motor/trans with all new clutch, pressure plate (PP), and throw out (TO) bearing. Clutch fork bushings all good, no slop, fork straight, rebuilt master and slave cylinders. After bleeding system, everything seems to be working fine except. While relaxed the rod out of the slave cylinder is tight on the fork. There is no free play at the fork at all. Seems tight and am concerned in this state the TO bearing is too tight on the PP. The motor and tranny have not yet been started or tested.

The clutch is definitely releasing and engaging for when in gear I can not turn the output flange of the tranny (no driveshaft installed yet) and with the clutch pedal in, I can move the flange easily by hand.

I scanned prior posts and could not find a good answer as to how much, if any, free play there should be. I would think one should feel a little slop. If a little free play is necessary how do we achieve this? Shorten the push rod out of the slave. Am I missing something?

??????Help

Thanks

jjs64bj8

 

[healeyblue]

this sounds normal to me on a hydraulic clutch system. Now you should have a little at the master clevis end.

 

[jjs64bj8]

healeyblue

I have very little free play at master cylinder. In fact the only play in the clutch pedal is a little slop in the clevis pin. Once that slop is taken up I can see the slave cylinder rod (fork) starting to move immediately as the clutch pedal is depressed. Estimated total stroke of the slave cylinder rod is about 1/2" when clutch pedal is depressed all the way to the floor. As I indicated the clutch seems to be engaging and disengaging properly. It has been a long time since the car has been together so I do not have much to compare it too.

I would think that since it is a hydraulic system it should be relaxed when no stroke on the master cylinder. But I still would think there should be some minimal movement at the fork. I mean it is tight.

Thanks

jjs64bj8

 

[Keoke]

Free play on the clutch should be about 3/8"

 

[jjs64bj8]

keoke thanks for the reply, but free play as measured where? If at the clutch pedal/master cylinder how get 3/8" when the rod is not adjustable? I know the pedal is all the way back when not depressed and is being stopped by the MC retainer circlip. So the MC push rod is not displacing any fluid. Help as I am really confused.

Thanks

jjs64bj8

 

[Keoke]

keoke thanks for the reply, but free play as measured where? If at the clutch pedal/master cylinder how get 3/8" when the rod is not adjustable? I know the pedal is all the way back when not depressed and is being stopped by the MC retainer circlip. So the MC push rod is not displacing any fluid. Help as I am really confused.

Get an adjustable push rod for the brake cylinder and install it on the clutch side.

 

[healeyblue]

The hydraulics should never be totally relaxed per se'. Like the hydraulics on brakes are never fully relaxed and returned to their start point, or you would have to re-pump the brakes to bring the calipers and pads back in close proximity to the rotor every time. If you have enough stroke to disengage the clutch disc, I would think you are fine.
Jim

 

[Keoke]

Heat generated in most hydraulic systems will be transferred to the fluid .Consequently, the fluid will expand and without some free play it can lock up the brakes.
They just did not see a need for the clutch but thermal conduction and other mechanical considerations justify the use of free play in the clutch in some instances.

 

[vette]

Pardon folks, but there can't be free play in the Hydralic part of a hydralic system. That would amout to air in the system. Air compresses at a much greater rate than hydralic fluid and would severly reduce the amount of pressure exerted by the system. Just like when there is air in the brakes. When you bleed your clutch you are removing all of the air or hopefully so. There then should be consistent fluid from the pressure side of the clutch master cyl piston to the pressure side of the slave cyl piston. When you are bleeding the clutch you are necessarily pushing the slave cyl pistion out as far as it can go without it pushing on the throwout release fork. There is no play. BUT AS SAID ABOVE YOU NEED TO HAVE ALITTLE PLAY IN THE CLEVIS AT THE TOP OF YOUR CLUTCH PEDAL. dAVE.

 

[Keoke]

Pardon folks, but there can't be free play in the Hydralic part of a hydralic system.

Good point Vette it is a mechanical adjustment.

 

[jjs64bj8]

Thanks for all the replies. I actually had a second slave cylinder push rod which was a hair shorter than the one installed. I replace the push rod and there was thus a little play. BUT as soon as I exercised the clutch pedal several times the play went away. I suppose this verifies what many have said, the system essentially adjusts itself. All seem to be working so we will see when we fire up the engine and check the tranny. So what happens when the clutch relaxes the pressure plate pushes back the throw out bearing to its relaxed position.


Again thanks

jjs64bj8

 

[healeyblue]

I agree too. When I referred to slack in the hydraulic side of the system I meant that the slave cylinder never returns to its fully compressed state, once bled. The pushrod will always be in contact with the throw out arm of the clutch.

 

[BOBBYR]

Pardon folks, but there can't be free play in the Hydralic part of a hydralic system.

Good point Vette it is a mechanical adjustment.

Hey Keoke, That was smooth. Bobby R

 

[steveg]

One would think there would be close to zero play in the system at rest. With foot removed from the clutch pedal, the hydraulic circuit is open back to the reservoir, and the clutch springs push the slave cylinder back to the point where the mechanism and slave piston come to a stop. With new clutch, etc, the slave piston would be very nearly seated.

Disc brakes would be similar, in that the only retracting mechanism is the runout on the rotor.