Diesel clutch master cylinder question

[biffa75]

This is something I feared, that the clutch needed replacing..

I'm "hoping" that the master cylinder is the cause.
There doesn't appear to be any leaks around the box/ engine as I've seen others say this is the slave leaking so that's okay.

The master is weeping and... As I found today, when changing gear, foot off the clutch, put your foot behind the pedal and attempt to pull the clutch pedal up with your foot. The pedal didn't move but.. it did have a very slight "thud" feeling through the pedal. After this, at 2k rpm, full throttle.. no clutch slip. Did this a few times to confirm and then went back to driving without putting my foot behind the clutch pedal and it appeared to slip again.

I maybe be clutching at straws here but.. I'm hoping the Luk master cylinder wasn't returning fully behind the pedal and effectively, acting as if the pedal was being used as a foot rest so very slight pressure still being applied..

If it does still slip afterwards, I have at least tried the easiest and cheapest option before removing the gearbox. After all, the master cylinder was leaking fluid anyway.

As the old saying goes..

"hope for the best, expect the worst"

Having seen the 75 tourer diesel in more detail doing the clutch doesn't both me there's loads of room

I'll report back. When I've finished the job,

Thanks guys

[macafee2]

Originally Posted by Number 6

Or NOT wanted to read....

opps sorry yes, I will go and amend my post

macafee2

[macafee2]

Personally I think a clutch change is a long job and day 1 should just be the day for undoing those seized nuts and bolts on the exhaust down pipe, silencer bracket, hub/damper.

My big problem was getting the gearbox and engine apart as they wanted to sit at different angles, Mike Noc came to my rescure. Also the bolts that hold the gearbox in place are different lengths, get some card, draw a large circle and put the bolts through the card in the right places.
The sub frame can be lowered and refitted by removing one of its bolts at a time and inserting a long 12mm threaded rod with nuts and large washers. Undo the nuts and the sub frame will lower. do up the nuts and the sub frame will rise.


The Haynes manual was very good on how to take it all apart.

good luck

macafee2

[biffa75]

Thanks for the advice macafee2.

A quick update*
The original Luk master cylinder (that was fitted to the car when the car was purchased only a few days ago) may have been causing the clutch slip, the slave wasn't leaking and the friction plate wasn't really worn.(could also have been the poor quality clutch kit that had been fitted?) Having removed it from the car and draining the fluid, we found the fluid was a gloopy black consistency and when drawing the push rod back and forth, you could feel when pulling the push rod back out, a sudden "slackness" became apparent. Waggling the end of the push rod revealed a sudden "thud" felt through your hands. We believe that a seal or something internal wasn't fully returning inside the cylinder which could also be the cause of the black goop in the bottom of the reservoir. Possibly the seals degrading and leaving traces against the bore walls causing the issue to be exacerbated perhaps? If this is the case, it could be giving the effect of someone sat with their foot partly on the clutch pedal, riding the clutch. Anyway... Was worth a try, the unit was leaking and it was getting difficult to engage 1st and reverse..

Changed the master cylinder for an AP unit and used the original pipework, bled the system a number of times to help flush out any gunk and black goop from the rest of the clutch hydraulics and... Unfortunately the clutch still slipped. The operation of the clutch pedal was a lot lot smoother and thankfully no more leaks.


I did fear that the damage may have already been done as we bought the car with the clutch already slipping (wasn't noticed in the test drive by my grandfather or by my wife who drove the car home, I couldn't go to view the car due to work).

Anyway.. today saw the gearbox being dropped out of the car, took little over an hour. With the clutch removed.. we quickly discovered a part number on the clutch friction plate. A quick eBay search revealed it to be an unbranded cheap clutch kit rated a heavy duty clutch kit??

We very quickly noticed.. the dmf was beyond re-using.. lots of stress cracks to the surface, lots of blue on the surface and a LOT of high spots.
High spots could also be seen on the clutch pressure plate too.

So with an Luk clutch kit ordered, dmf being collected tomorrow and a new guide tube and drive shaft oil seals.. hopefully this will put an end to this slippy clutchy business.

Thanks have to go to my brother who removed the gearbox while I was in bed having been on nights. He said it was one of the easiest gearbox removals he has done. (Me and my brother have done a few clutches over the years and some were a real PITA.

On a side note, while diving into the job, we know the egr has been blanked off, it has had the inline thermostat mod fitted.. I'm thinking at some point if the clutch all goes okay of visiting big Russ and seeing if he can tell me if it has had the 160map done.

Quick question tho guys..

The fly wheel bolts, are these re-usable or are new ones required?

Thanks
Rob

[macafee2]

Originally Posted by biffa75

Thanks for the advice macafee2.

A quick update*
The original Luk master cylinder (that was fitted to the car when the car was purchased only a few days ago) may have been causing the clutch slip, the slave wasn't leaking and the friction plate wasn't really worn.(could also have been the poor quality clutch kit that had been fitted?) Having removed it from the car and draining the fluid, we found the fluid was a gloopy black consistency and when drawing the push rod back and forth, you could feel when pulling the push rod back out, a sudden "slackness" became apparent. Waggling the end of the push rod revealed a sudden "thud" felt through your hands. We believe that a seal or something internal wasn't fully returning inside the cylinder which could also be the cause of the black goop in the bottom of the reservoir. Possibly the seals degrading and leaving traces against the bore walls causing the issue to be exacerbated perhaps? If this is the case, it could be giving the effect of someone sat with their foot partly on the clutch pedal, riding the clutch. Anyway... Was worth a try, the unit was leaking and it was getting difficult to engage 1st and reverse..

Changed the master cylinder for an AP unit and used the original pipework, bled the system a number of times to help flush out any gunk and black goop from the rest of the clutch hydraulics and... Unfortunately the clutch still slipped. The operation of the clutch pedal was a lot lot smoother and thankfully no more leaks.


I did fear that the damage may have already been done as we bought the car with the clutch already slipping (wasn't noticed in the test drive by my grandfather or by my wife who drove the car home, I couldn't go to view the car due to work).

Anyway.. today saw the gearbox being dropped out of the car, took little over an hour. With the clutch removed.. we quickly discovered a part number on the clutch friction plate. A quick eBay search revealed it to be an unbranded cheap clutch kit rated a heavy duty clutch kit??

We very quickly noticed.. the dmf was beyond re-using.. lots of stress cracks to the surface, lots of blue on the surface and a LOT of high spots.
High spots could also be seen on the clutch pressure plate too.

So with an Luk clutch kit ordered, dmf being collected tomorrow and a new guide tube and drive shaft oil seals.. hopefully this will put an end to this slippy clutchy business.

Thanks have to go to my brother who removed the gearbox while I was in bed having been on nights. He said it was one of the easiest gearbox removals he has done. (Me and my brother have done a few clutches over the years and some were a real PITA.

On a side note, while diving into the job, we know the egr has been blanked off, it has had the inline thermostat mod fitted.. I'm thinking at some point if the clutch all goes okay of visiting big Russ and seeing if he can tell me if it has had the 160map done.

Quick question tho guys..

The fly wheel bolts, are these re-usable or are new ones required?

Thanks
Rob

Rob you have some brother, treat him well.
thanks for the update, looks like you are well on the way to sorting this out

macafee2

[biffa75]

He's certainly a good one. We help each other out when it comes to repairs and restoration work stuff.

We are all hoping the new dmf and clutch kit solves the issue and we get some miles from it.

Having compared the new dmf to the existing flywheel at 81k miles.. even though it is within the 25mm tolerance, the existing flywheel seemed very... Sloppy, being able to expand the springs by turning the flywheel by hand.. the new dmf, you have very little free play before the springs come into it and then trying to turn it against the springs by hand is impossible.

Would it be unreasonable to wonder if the clutch hydraulic failure rates could be related to the dmf not being changed, even though it is within the 25mm tolerance?

Rob

[alanaslan]

Originally Posted by trikey

Nope, a leaking master would make gear changes difficult but once the gear is engaged, the master is taken out of the equasion.

A worn friction plate or a leaky slave can cause clutch slip.

Just as a matter of interest the difference in the thickness of a new friction plate and totally worn out one is 100 thousands of an inch.
Not much meat to play with but in the M47R I have seen nearly 200,000 miles on one plate. Useless facts from my senile old brain.


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[alanaslan]

Originally Posted by biffa75

Thanks for the advice macafee2.

A quick update*
The original Luk master cylinder (that was fitted to the car when the car was purchased only a few days ago) may have been causing the clutch slip, the slave wasn't leaking and the friction plate wasn't really worn.(could also have been the poor quality clutch kit that had been fitted?) Having removed it from the car and draining the fluid, we found the fluid was a gloopy black consistency and when drawing the push rod back and forth, you could feel when pulling the push rod back out, a sudden "slackness" became apparent. Waggling the end of the push rod revealed a sudden "thud" felt through your hands. We believe that a seal or something internal wasn't fully returning inside the cylinder which could also be the cause of the black goop in the bottom of the reservoir. Possibly the seals degrading and leaving traces against the bore walls causing the issue to be exacerbated perhaps? If this is the case, it could be giving the effect of someone sat with their foot partly on the clutch pedal, riding the clutch. Anyway... Was worth a try, the unit was leaking and it was getting difficult to engage 1st and reverse..

Changed the master cylinder for an AP unit and used the original pipework, bled the system a number of times to help flush out any gunk and black goop from the rest of the clutch hydraulics and... Unfortunately the clutch still slipped. The operation of the clutch pedal was a lot lot smoother and thankfully no more leaks.


I did fear that the damage may have already been done as we bought the car with the clutch already slipping (wasn't noticed in the test drive by my grandfather or by my wife who drove the car home, I couldn't go to view the car due to work).

Anyway.. today saw the gearbox being dropped out of the car, took little over an hour. With the clutch removed.. we quickly discovered a part number on the clutch friction plate. A quick eBay search revealed it to be an unbranded cheap clutch kit rated a heavy duty clutch kit??

We very quickly noticed.. the dmf was beyond re-using.. lots of stress cracks to the surface, lots of blue on the surface and a LOT of high spots.
High spots could also be seen on the clutch pressure plate too.

So with an Luk clutch kit ordered, dmf being collected tomorrow and a new guide tube and drive shaft oil seals.. hopefully this will put an end to this slippy clutchy business.

Thanks have to go to my brother who removed the gearbox while I was in bed having been on nights. He said it was one of the easiest gearbox removals he has done. (Me and my brother have done a few clutches over the years and some were a real PITA.

On a side note, while diving into the job, we know the egr has been blanked off, it has had the inline thermostat mod fitted.. I'm thinking at some point if the clutch all goes okay of visiting big Russ and seeing if he can tell me if it has had the 160map done.

Quick question tho guys..

The fly wheel bolts, are these re-usable or are new ones required?

Thanks
Rob

This is just another reason for hydraulic fluid lines to be fully flushed every five years and checked for water content every service or every year which ever comes first. You can pick up a reasonable electronic hydro check sensor for about £30.
If the fluid Is black and lumpy then the muck has to have come from somewhere. Seals passing or rubber hoses degrading.
The clutch in the M47R is not that bad a job. The question you have to ask yourself is whither to replace the DMF or not. Also do you fit another DMF or a solid flywheel. All the DMF does is make for a smoother gear change. Despite what some companies claim.
If a car needed a DMF to protect the drive train or crank. This retired engineer is a monkeys Uncle. The words utter bumpkin spring to mind. I remember being invited as a guest lecturer to a University in the midlands. The man up before me explained to the students why DMFs were required. I felt terrible when I proved with maths that his reasoning was out the window and the combustion forces on the crank exceeded by up to 8 fold the torque exerted by the flywheel. During coffee at the lunch time break the proff and I sat and discussed the pros and cons. Taking the manufacturer’s data and then disproving it with the mathematical model. He was astounded that so many manufacturers needlessly fitted expensive flywheels where a balanced lump of metal would do a better job and would reduce wear on crank oil seal wear.
We came to the conclusion it was so they could charge more to carry out a clutch change.
A bit like aero manufactures selling engines at anything to a million pounds less than cost. Knowing that over the next three years you will recoup that loss and then some with the sale of service parts.
Goodness knows what will happen when we go electric. If anybody knows of a company that can recycle lithium polymer batteries please let me know so I can buy shares in them. There is a mint to be made if it can be done. Then again dig a hole and drop them in who cares.


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[MSS]

Originally Posted by alanaslan

..............


The question you have to ask yourself is whither to replace the DMF or not. Also do you fit another DMF or a solid flywheel. All the DMF does is make for a smoother gear change. Despite what some companies claim.

If a car needed a DMF to protect the drive train or crank. This retired engineer is a monkeys Uncle. The words utter bumpkin spring to mind. I remember being invited as a guest lecturer to a University in the midlands. The man up before me explained to the students why DMFs were required. I felt terrible when I proved with maths that his reasoning was out the window and the combustion forces on the crank exceeded by up to 8 fold the torque exerted by the flywheel. During coffee at the lunch time break the proff and I sat and discussed the pros and cons. Taking the manufacturer’s data and then disproving it with the mathematical model. He was astounded that so many manufacturers needlessly fitted expensive flywheels where a balanced lump of metal would do a better job and would reduce wear on crank oil seal wear.

We came to the conclusion it was so they could charge more to carry out a clutch change.

A bit like aero manufactures selling engines at anything to a million pounds less than cost. Knowing that over the next three years you will recoup that loss and then some with the sale of service parts.

Goodness knows what will happen when we go electric. If anybody knows of a company that can recycle lithium polymer batteries please let me know so I can buy shares in them. There is a mint to be made if it can be done. Then again dig a hole and drop them in who cares.

Alan, What you say about DMF is interesting but I am sure you are more than aware that maths is only relevant if your mathematical model of the physical processes is representative.

As what you say will surprise most members of the forum, especially those such as marinabrian who have a lot of experience of the impact of DMF replacement with a solid flywheel, would you mind sharing details of your mathematical model and associated calculations please?

There is a basic flaw in your argument comparing ownership cost model of an aero engine with that of a car fitted with a DMF. DMF are not part of service schedules and are expected to last the car's lifetime, which they do in near 100% of cases. They do not therefore inflate the cost of a clutch change except in the very, very small percentage of failure situations. Such percentages will be irrelevant in terms of average cost inflation from a car manufacturer's perspective.

By comparison, aero engine servicing is a major element of the cost of ownership and a critical part of operating an aero engine. Without it, an aero engine becomes worthless and unusable.

Also, is it not the case that a DMF reduces the transient forces on the drivetrain at clutch engage time?

Thank you.

Perhaps you can respond in a new thread specifically for the purpose of discussing the needs for a DMF and impacts of solid flywheel replacement?

[HarryM1BYT]

Originally Posted by MSS

Perhaps you can respond in a new thread specifically for the purpose of discussing the needs for a DMF and impacts of solid flywheel replacement?

I'm with you on this point. My understanding of the DMF's purpose is that it helps smooth out and regulate the pulses of speed of the engine, as it fires. Rather than using a big, heavy flywheel to smooth it out, the flywheel can be much lighter making the engine more responsive, but avoiding the vibration of power delivery via the cushioning effect of a DMF.


I suspect it will make little difference so far as the smoothness of the gear change and take up.