Ur MB hydraulic clutch adjustment

BackintheFold · 23-07-22, 04:06 PM

How are you supposed to adjust the clutch?
Mines had a new clutch maybe 3,000 miles ago and the bite point is very high.
So I’m barely touching the pedal and it’s disengaging. I’d like it a little further down the travel.

I’ve got the lower dash trim off and I can see the master cylinder locknut.

Do I loosen the nut off, then rotate the pushrod so it screws into the lever/arm?
That is, so that the pushrod that goes in to the master cylinder is effectively shorter? How do I know when it is the right length? Or can it fall out or otherwise be damaged by me doing what I’ve said above?

I can’t even touch the pushrod at the other end of the lever that is allegedly connected to the pedal!! So adjustment there is currently not an option.

Open to suggestions!
Thanks

BackintheFold · 23-07-22, 04:23 PM

I’m thinking I should remove the pin at the end of the master push rod, adjust the pushrod until the pin and hole are lined up by the fluid pressure from the slave pushing back up from the clutch, then lock the locknut and keep
My fingers crossed.

Sound acceptable?

I am assuming the pushrod has been adjusted too long.

Groundhog · 24-07-22, 01:19 PM

You cannot adjust the clutch per-se, you can only adjust the free play which in any event should never need doing. I assume you have a little free play? And I assume the clutch pedal is level with the brake (i.e the pedal stop rubber missing/failed)
Do you know for a fact it was replaced and not just in part or with a secondhand unit or a particularly inferior brand?
I would say , from your brief description and without experiencing the ‘drive’, that it has got issues.

BackintheFold · 24-07-22, 01:30 PM

I have the receipt for a new clutch and the PO said he’d had it changed.

The issue I have is no free play that I can see/feel in the pedal.

I’ve poked around this morning, and I have a plan (for another day).

First,remove the pin from the master pushrod to the lever. Allow that to find its seating position from the clutch and slave pushing the hydraulic fluid back up the pipes.

Then somehow adjust either the length of the pushrod or the length of the pull rod to get the hole in the lever to line up with the master push road hole and replace the pin.

There doesn’t appear to be an easy way to do this. Just the least difficult!

tractor Dave · 24-07-22, 03:02 PM

Maybe an incorrect aftermarket slave has been used. If the rod length of the slave is incorrect you will get this very symptom.

Groundhog · 24-07-22, 03:28 PM

I assume you mean master?…….in all the many hundreds of master cylinders I changed ‘back then’ I discarded the threaded pin that came with the cylinder and left the original attached to the pedal. It could be that someone went to the lengths to swap the yolk and locknut over and got the length wrong- hence the problem. Trouble is if there is no free play then it is equivalent to driving with your foot permanently resting on the clutch pedal, result = premature worn out clutch.

tractor Dave · 24-07-22, 05:38 PM

I've only ever seen this on the slave but master will have the same effect. On the one I saw an aftermarket slave rod was too long so it was acting on the clutch slightly before you even started pressing the pedal.

Hanuman · 24-07-22, 05:42 PM

Replacement cylinders came with all the required hardware for as long as I have been an owner. One prevailing wisdom was to use the original rod, if memory serves. Thus avoiding having to make any adjustments to a rod. It’s been a long time since I did one.
It may be that a cylinder has been replaced, and/or the rod has been adjusted to cater for a deteriorating mechanism or clutch?

BackintheFold · 24-07-22, 09:15 PM

Han.. that is my thought.
That the pedal was adjusted to make up for a worn clutch, then a new clutch fitted without resetting the pedal.
It could also be the wrong length rod having been used.

It would be SUCH a simple job to check this if it wasn’t for poor access!

The bottom line is I need to get the master push rod pin out so I can find where the clutch and slave wants to place it (regardless of whether the problem is wrong length rod(s) or incorrect adjustment), then adjust the push and pull rods to allow that.

There’s been a noise ever since I bought the car that I’ve been unable to pin down. I thought I was just being over sensitive. Now it strikes me it may be the clutch release bearing being slightly engaged.

I won’t be using the car for August so I may have time to give it a go without worrying about it being immobile if I get stuck! I can see me removing the pin and then not being able to adjust the rod length and so being unable to put the pin back in! The joy…

I think once I’ve removed the master/pin, and start getting my hands dirty I’ll
Be able to figure it out better. There’s two
Places to adjust (master rod and pedal rod). Is the master rod fixed in the master cylinder? I mean, is it possible to remove the rod just by pulling it out of the cylinder? Does it just sit in a “cup”? Or is it attached so if I had it in front of me and I pulled it I’d pull all sorts of seals out with it?

Can I rotate the master rod?
Is the pedal road set up with a right hand and a left hand thread, so I can loosen the locknut and rotate the pedal rod to adjust the length ? (If it was same threaded at both ends rotating it would just tighten one end and loosen the other, meaning the length would remain the same.

Really simple to work out if I had them on a bench, but I’m not even sure I can undo the master rod locknut in situ.
I think I will End up having to remove the master rod pin, and adjust on the pedal
rod. Maybe some long thin pliers will enable
Me to rotate the pedal rod, and I can figure out which way to do it by trial and plenty of error!

Hanuman · 25-07-22, 06:31 AM

I’m currently not in UK/Europe, otherwise, I’d take a photo of the entire pedal box that I’ve got, spare.

I vaguely recall that the rod simply screws out, and uses a locknut, to set its length. There may be a set length in the Bentley manual.

Access is crap, but.
If you’re reasonably flexible, an hour on your back with a 1/4” drive socket set will have all the bits in your hands.

The pedal has a stop position. It’s usually not in great condition. Pivot and actuation are not really adjustable.

Left drive version, here
https://audi.7zap.com/en/rdw/audi+qu...6/7/721-59000/

Right hand drive coupe/quattro May give more clarity
https://audi.7zap.com/en/rdw/audi+co...8/7/721-76020/

If I remember correctly, the bellows on the master cylinder push rod holds the rod in place, but the rod is simply a rounded end acted upon by the cylinder. Hence, part of the don’t adjust, reuse philosophy. But it’s a very long while since I did one.

23-07-22, 04:23 PM	#2
BackintheFold Senior Member Classic Audi Club Member Join Date: Feb 2019 Location: Near an MB ur Quattro Posts: 1,190	I’m thinking I should remove the pin at the end of the master push rod, adjust the pushrod until the pin and hole are lined up by the fluid pressure from the slave pushing back up from the clutch, then lock the locknut and keep My fingers crossed. Sound acceptable? I am assuming the pushrod has been adjusted too long. __________________ 2006 A3 (daily drive) 1987 MB ur

24-07-22, 01:30 PM	#4
BackintheFold Senior Member Classic Audi Club Member Join Date: Feb 2019 Location: Near an MB ur Quattro Posts: 1,190	I have the receipt for a new clutch and the PO said he’d had it changed. The issue I have is no free play that I can see/feel in the pedal. I’ve poked around this morning, and I have a plan (for another day). First,remove the pin from the master pushrod to the lever. Allow that to find its seating position from the clutch and slave pushing the hydraulic fluid back up the pipes. Then somehow adjust either the length of the pushrod or the length of the pull rod to get the hole in the lever to line up with the master push road hole and replace the pin. There doesn’t appear to be an easy way to do this. Just the least difficult! __________________ 2006 A3 (daily drive) 1987 MB ur

24-07-22, 05:42 PM	#8
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,016	Replacement cylinders came with all the required hardware for as long as I have been an owner. One prevailing wisdom was to use the original rod, if memory serves. Thus avoiding having to make any adjustments to a rod. It’s been a long time since I did one. It may be that a cylinder has been replaced, and/or the rod has been adjusted to cater for a deteriorating mechanism or clutch? __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor

24-07-22, 09:15 PM	#9
BackintheFold Senior Member Classic Audi Club Member Join Date: Feb 2019 Location: Near an MB ur Quattro Posts: 1,190	Han.. that is my thought. That the pedal was adjusted to make up for a worn clutch, then a new clutch fitted without resetting the pedal. It could also be the wrong length rod having been used. It would be SUCH a simple job to check this if it wasn’t for poor access! The bottom line is I need to get the master push rod pin out so I can find where the clutch and slave wants to place it (regardless of whether the problem is wrong length rod(s) or incorrect adjustment), then adjust the push and pull rods to allow that. There’s been a noise ever since I bought the car that I’ve been unable to pin down. I thought I was just being over sensitive. Now it strikes me it may be the clutch release bearing being slightly engaged. I won’t be using the car for August so I may have time to give it a go without worrying about it being immobile if I get stuck! I can see me removing the pin and then not being able to adjust the rod length and so being unable to put the pin back in! The joy… I think once I’ve removed the master/pin, and start getting my hands dirty I’ll Be able to figure it out better. There’s two Places to adjust (master rod and pedal rod). Is the master rod fixed in the master cylinder? I mean, is it possible to remove the rod just by pulling it out of the cylinder? Does it just sit in a “cup”? Or is it attached so if I had it in front of me and I pulled it I’d pull all sorts of seals out with it? Can I rotate the master rod? Is the pedal road set up with a right hand and a left hand thread, so I can loosen the locknut and rotate the pedal rod to adjust the length ? (If it was same threaded at both ends rotating it would just tighten one end and loosen the other, meaning the length would remain the same. Really simple to work out if I had them on a bench, but I’m not even sure I can undo the master rod locknut in situ. I think I will End up having to remove the master rod pin, and adjust on the pedal rod. Maybe some long thin pliers will enable Me to rotate the pedal rod, and I can figure out which way to do it by trial and plenty of error! __________________ 2006 A3 (daily drive) 1987 MB ur Last edited by BackintheFold; 24-07-22 at 09:20 PM.

25-07-22, 06:31 AM	#10
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,016	I’m currently not in UK/Europe, otherwise, I’d take a photo of the entire pedal box that I’ve got, spare. I vaguely recall that the rod simply screws out, and uses a locknut, to set its length. There may be a set length in the Bentley manual. Access is crap, but. If you’re reasonably flexible, an hour on your back with a 1/4” drive socket set will have all the bits in your hands. The pedal has a stop position. It’s usually not in great condition. Pivot and actuation are not really adjustable. Left drive version, here https://audi.7zap.com/en/rdw/audi+qu...6/7/721-59000/ Right hand drive coupe/quattro May give more clarity https://audi.7zap.com/en/rdw/audi+co...8/7/721-76020/ If I remember correctly, the bellows on the master cylinder push rod holds the rod in place, but the rod is simply a rounded end acted upon by the cylinder. Hence, part of the don’t adjust, reuse philosophy. But it’s a very long while since I did one. __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor

24-07-22, 01:19 PM	#3
Groundhog Grown up member Join Date: Nov 2009 Posts: 143	You cannot adjust the clutch per-se, you can only adjust the free play which in any event should never need doing. I assume you have a little free play? And I assume the clutch pedal is level with the brake (i.e the pedal stop rubber missing/failed) Do you know for a fact it was replaced and not just in part or with a secondhand unit or a particularly inferior brand? I would say , from your brief description and without experiencing the ‘drive’, that it has got issues.

24-07-22, 03:02 PM	#5
tractor Dave Senior Member Classic Audi Club Member Join Date: Apr 2018 Location: Wales Posts: 1,174	Maybe an incorrect aftermarket slave has been used. If the rod length of the slave is incorrect you will get this very symptom.

24-07-22, 03:28 PM	#6
Groundhog Grown up member Join Date: Nov 2009 Posts: 143	I assume you mean master?…….in all the many hundreds of master cylinders I changed ‘back then’ I discarded the threaded pin that came with the cylinder and left the original attached to the pedal. It could be that someone went to the lengths to swap the yolk and locknut over and got the length wrong- hence the problem. Trouble is if there is no free play then it is equivalent to driving with your foot permanently resting on the clutch pedal, result = premature worn out clutch.

24-07-22, 05:38 PM	#7
tractor Dave Senior Member Classic Audi Club Member Join Date: Apr 2018 Location: Wales Posts: 1,174	I've only ever seen this on the slave but master will have the same effect. On the one I saw an aftermarket slave rod was too long so it was acting on the clutch slightly before you even started pressing the pedal.