New Clutch Hydraulic System

Evening, All.

Today I replaced both clutch master and slave cylinders and fitted a pedal box I had reconditioned that already had the new master cylinder in it. The new pedal box is the later type with the double curly spring. When it came to filling the system with clutch fluid and bleeding it, the pedal was so light that I thought there was a problem somewhere. First gear now engages without a battle and gear changes are smoother. Is the difference the spring makes really this great? The only slight fly in the ointment is that, no matter how much I try, I can't get the advised 140mm height on the clutch pedal, despite adjusting away like mad. Also, is the return spring still necessary? I've fitted it anyway. I'm told the system will improve and self bleed to a degree, which is good news as the slave bleed nipple, while reasonably accessible, is difficult to rotate enough to bleed easily.

Many thanks,

Dom

Hi Dom,

I changed mine from the single tension spring to the as you call it double coil spring, Yes it does make a big difference, I did not refit the single tension spring. although only to the force required, not the gear selection itself. I take it you have tried adjusting the MC to get the 140mm ?

It has been recommended on here in the past, to use a stick to hold the pedal down overnight to help it bleed. I found reverse bleeding helped with the bleeding and a final normal bleed, but make sure the vehicle is higher at the front. ( plus the bleed nipple is at the top of the slave cylinder).

Cheers

Thanks, neilly.

Yes, the bleed nipple is at the top. I've just looked at the diagram and am confused by the nut on the front face of the pedal box in terms of which way does what! If I screw it in (having slackened off the locknuts on the MC pushrods, will that raise pedal height?

Many thanks,

Dom

Hi Dom,

Did you read this?


Cheers

Yes, I did. It looks like if I screw in item 4 it will raise the pedal height. Can you please confirm this?

Maybe I didn't introduce enough free play between the pushrod and the MC piston. I'll have another go when it stops raining!

domderbyshire said:

Yes, I did. It looks like if I screw in item 4 it will raise the pedal height. Can you please confirm this?

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Hi Dom, When I had the issues with mine I found the measurements were correct,So I never had to play with it .
But item 4 looks like the pedal pushed down stop position, not anything to do with pedal up position. If it was not raining here I would go and check. ..LOL
How have you been trying to adjust it?

Cheers

In that case, it's got to be the free play between the end of the pushrod and the MC piston. It's raining here, too, but I'm tempted to have a go as the job has gone really well, but it bugs me when things aren't quite right!

If you think about it,

If you adjust the lock nuts, marked as item 2 towards the left of the page as shown above then the pedal will move upwards from the floor.
Having said that, as long as the pedal moved correctly, has the gaps required to make sure it is working correctly, I am not sure I would get hung up on the pedal height being slightly off.

Cheers

Well, it works and I know I'm close, so that's not too bad. At least I understand better now. Thank you very much for your help.

I am going to go and have a look at mine in the morning providing the storms do not stop play.

Cheers

Me, too. I look forward to hearing from you!

I couldn't resist another go at adjusting the setup in the rain last night with a torch.... Item 4 in the diagram, when screwed in, makes the pedal move closer to the floor. At the moment I've unscrewed it to the point whereby I can have the pedal as high as possible with it only just touching the armature in the pedal box when the pedal is fully released. I also wound the lock nuts as far away from the bulkhead as possible and the pedal height seems fine in the car, even if it's still not quite 140mm. As for free play between the push rod and the MC piston, I'm not quite sure how to set and measure that. There is a little movement in the pedal before pressure is felt, so I presume I'm not preloading the system and risking clutch slip. The car drove fine on a test drive last night. I'm still amazed by (and slightly nervous about) how much lighter the clutch action now is. I reckon another bleed might be necessary once everything has settled. I tried the block of wood trick overnight and have yet to drive the car today, so we'll see if that helped.

Tried a quick bleed this morning, having left the pedal depressed overnight. The pedal is light, but smooth. Gear changes are nice and there's no clutch slip. Job's a good'un.

Pleased to hear it!

Hi @domderbyshire

I am not sure why, ( it must be a LR thing) but as it has just stopped raining, I have been and looked at mine. Unfortunately, I cannot adjust bolt 4 , as it is seized ( currently having a soak in ATF/Acetone mix) but , from what I can see shining a torch down there and moving the pushrod / pedal lever fully forward in the pedal box, item 4 is the stop position for the pedal fully down position. So it stops you mashing the pedal thru the floor.

Having said that, my item 4 is further down in the pedal box so it acts as pedal down stop, the way it is in the drawing it does as you say and adjusts the pedal up position. Might be because mine is a l'ill bit of a bitsa 90.

Cheers

Yes, mine's only a humble 200 Tdi. I swapped the pedal box as I felt it was easier to buy a second hand one, strip it and repaint it etc on the bench, while also fitting the MC off the car. An ulterior motive was to generate a lighter clutch action by using a later box with the double coil spring. Driving the car today was a pleasure and I'm pleased with the job. It wasn't hard, but filling a completely empty system and bleeding it caused me a bit of worry.

I'm still not sure if there's actually any free play between the MC and the push rod, but the clutch doesn't slip, the car idles correctly and there is some downward movement in the clutch pedal before it disengages, so I'm presuming that's ok.

One small thing that's niggling me is the lack of a washer between one of the lock nuts and the trunion. There wasn't one when I stripped the donor pedal box, so I went with that. Having looked at numerous images on the internet, I think there should be. Anyway, it's easy enough to rectify.

Oldseadog said:

Pleased to hear it!

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Thank you!