Confirmation about clutch fluid...

[Mike V]

Evening all,

I have used the search feature to find out as much as I can about the clutch hydraulic system.

Im a little confused about the set up though due to reading different things.
Haynes for example says 'Brake (and clutch) fluid' yet some one on the forum said 'Haynes has it wrong'
Is the brake fluid a seperate system to the clutch?

I am considering having the clutch fuide changed but then I read that it shouldnt as it is a 'sealed for life system'...

(All this is in regards to having a stiff gear change. Yet clutch seems fine. Pulls well in 4th at 30mph.)

[Phil]

Hi, the clutch and brake fluid is totally separate. The clutch fluid reservoir is above the pedal, inside the car. Very hard to get to! It is said to be sealed for life, but it isn't.

[T-Cut]

There's precious little fluid in the clutch reservoir. This is due to its small size and also due to a voluminous plastic insert which seems to serve little purpose. If the insert is removed permanently, you can almost double the fluid capacity. And with a clutch system as precarious as this one is, every little helps.

TC

[HarryM1BYT]

The clutch master cylinder is directly above your toe as you press the clutch pedal. You will need to remove the cover panel to be able to see it and it is still awkward to see. Remove the top with its black insert and cut the insert down so it just leaves the upper part in place to form a seal - then you can get much more fluid in.

There is a bleed nipple on top of the gearbox visible below the battery/ between battery and engine at the bottom.

[Mike V]

Thanks for the reply guys. I will investigate further tomorrow. There is a Rover garage near me aswell so I might drop by and have a chat witht the guys. See how much they charge for a change etc. Sounds like its worth a go. According to the paper work it has never been done. (car at 60k)

[Mike V]

The clutch master cylinder is directly above your toe as you press the clutch pedal. You will need to remove the cover panel to be able to see it and it is still awkward to see. Remove the top with its black insert and cut the insert down so it just leaves the upper part in place to form a seal - then you can get much more fluid in.

There is a bleed nipple on top of the gearbox visible below the battery/ between battery and engine at the bottom.


Thanks Harry, there is a picture on here somewhere I spotted showing the nipple. I saw it when re-searching before so I know where you mean.

[HarryM1BYT]

I was advised that all metal pipes down there mean it has had a replacement slave cylinder, so maybe a new clutch too.

It will not take much bleeding before the master is emptied, so fill it before your start. I found it easiest to use some aquirium type plastic air pipe, with a bit of thin steel wire down the pipe at the cylinder end, to enable an hook to be formed to make it stay put on the cylinder. A large syringe body in the other end of the pipe, makes it easy to pour in the DOT4, if it is held high and lots of newspaper to catch the spills on the carpet.

[Phil]

Just my opinion but I wouldn't snip the seal down, I agree that it is too big but it serves a purpose to seal the system from the atmosphere.
Brake fluid is hygroscopic so absorbs water, if the brake fluid absorbs water it won't do what it is meant to.
The idea of the big seal is to allow the drop and rise of brake fluid in the reservoir without creating pressure or vacuum when the pedal is depressed. Hence there is a vent hole drilled in the reservoir cap.

[HarryM1BYT]

A normal hydralic system (brake and clutch) has a vent and are not sealed from the atmosphere. Rover put the seal in to make it a sealed for life system, unfortunately making the capacity for fluid tiny - not enough for the very slightest of fluid loss. Probably their idea was that it was less costly to mount it there where it could not be so easily maintained, but call it maintanance free for life.

If the system is to be maintained, then there is no longer any real need for it to be air sealed. Likely changing the fluid more frequently will prolong its life, rather than never touching it.

[Phil]

A normal hydralic system (brake and clutch) has a vent and are not sealed from the atmosphere. Rover put the seal in to make it a sealed for life system, unfortunately making the capacity for fluid tiny - not enough for the very slightest of fluid loss. Probably their idea was that it was less costly to mount it there where it could not be so easily maintained, but call it maintanance free for life.

If the system is to be maintained, then there is no longer any real need for it to be air sealed. Likely changing the fluid more frequently will prolong its life, rather than never touching it.

Hi, I am more than likely wrong but I can't think of any brake or clutch circuit with a vent to the atmosphere on any model? :o

[HarryM1BYT]

Every hydraulic system has to have some sort of vent in the master cylinder, above the level of the fluid. Large commercial/ industrial hydraulic units have a vent often sealed with a drying filter.

The top of the 75's brake master cylinder has a vent in it, to allow air in surely? If it didn't, then as the brake pads wore down the fluid in the cylinder would be under a slight vacuum.

Modern motorcycles which use hydraulics for clutch or brakes, use a similar semi-sealed system. Mine uses hydraulics for both F&R brakes and the clutch.

The cover of the master cylinders have a diaphram which forms a seal between fluid and air, but yet allow the fluid level to fall. The top covers have an vent to allow air in above the diaphram. The seal is like a shallow rubber bellows. That pretty much describes the idea behind the seal in the clutch master cylinder of the 75's clutch.

[Mike V]

Update: I removed the cover above the pedals to inspect the clutch master cylinder. Here is what I found:

A light trace of something dripping down. I couldnt take a pic as my sister has borrowed the camera. But here is a mock up..

http://c.imagehost.org/0483/Leaking_slave.jpg

What do you guys think? Is it possible the clutch has leaked slightly or is this just the remnants of some lubricant used on the piston?

[HarryM1BYT]

The only way to prove it is a leak, is to dry it all off thoroughly and see if more fluid appears. Did you check the fluid level in the cylinder? you can't really check it except by putting a finger down into the cylinder.

Some suggest it makes the pedal easier to operate, if some lubricant is sprayed around the area of the pivot - hopefully your 'leak' might just be where someone has attempted to lubricate it.

[Mike V]

The only way to prove it is a leak, is to dry it all off thoroughly and see if more fluid appears. Did you check the fluid level in the cylinder? you can't really check it except by putting a finger down into the cylinder.

Some suggest it makes the pedal easier to operate, if some lubricant is sprayed around the area of the pivot - hopefully your 'leak' might just be where someone has attempted to lubricate it.

Im hoping so Harry. I couldnt check the level on the side and didnt want to open it and put any fingers in. Like you say Il clean it and see how I go. Theres a chance someone has tried something before as one of the screws was missing from the panel above the pedals.

[COLVERT]

Just my opinion but I wouldn't snip the seal down, I agree that it is too big but it serves a purpose to seal the system from the atmosphere.
Brake fluid is hygroscopic so absorbs water, if the brake fluid absorbs water it won't do what it is meant to.
The idea of the big seal is to allow the drop and rise of brake fluid in the reservoir without creating pressure or vacuum when the pedal is depressed. Hence there is a vent hole drilled in the reservoir cap.
The reason people talk about water absorbtion in the brake fluid being detrimental is because if it reaches the brake calipers it can possibly be turned to steam with total brake loss. OUCH !!! However moisture in the clutch fluid is hardly worth bothering about because the system runs almost COLD. ie. it doesn't need changing.
Once the clutch system starts to leak topping up is hardly worth the trouble because the leak is due to wear and no amount of topping up will make THAT go away.

Colvert. :shrug: :getmecoat:

[COLVERT]

Update: I removed the cover above the pedals to inspect the clutch master cylinder. Here is what I found:

A light trace of something dripping down. I couldnt take a pic as my sister has borrowed the camera. But here is a mock up..

http://c.imagehost.org/0483/Leaking_slave.jpg

What do you guys think? Is it possible the clutch has leaked slightly or is this just the remnants of some lubricant used on the piston?
There are two seals. The one that operates the clutch and the other one which seals the operating rod to the inside of the car. The rod seal is the one that has gone.If the other seal has gone then you will not be able to operate the clutch.


Colvert.

[T-Cut]

I have been told that the clutch reservoir cap has a vent hole in it. I'm slightly surprised, because I have always assumed that the internal 'condom' gizmo was to allow the fluid to maintain its equilibrium pressure by allowing the condom to expand and contract. If that's not the case, and the cap does indeed have a vent hole, then why on Earth did they fit it?

TC

[HarryM1BYT]

I have been told that the clutch reservoir cap has a vent hole in it. I'm slightly surprised, because I have always assumed that the internal 'condom' gizmo was to allow the fluid to maintain its equilibrium pressure by allowing the condom to expand and contract. If that's not the case, and the cap does indeed have a vent hole, then why on Earth did they fit it?

TC

To be absolutely honest, I just assumed that there had to be a vent in the cap - I didn't actually think to confirm it. As already said, the diaphram/condom is there just to prevent the air from getting to the fluid and thus allowing the moisture from the air into the fluid.

There really has to be a vent, otherwise temperature variations and small amounts of fluid loss would cause enough pressure to cause it not work.

My bikes front brake and clutch levers each have a master cyclinder mounted on the handlebars. The cylinders are a little smaller than a 10 pack of ciggarettes, laid flat down and cast from alloy. The side upper most is removable for topping up etc.. Directly under the cover is a bellows like flexible diaphram to keeping the air away from the fluid, which is able to expand into the master cylinder as the fluid level changes. Above the diaphram is vented to the atmosphere by breather which zig-zags its way out to a vent - to prevent dirt and wet getting in. The diaphram not only keeps the air and fluid apart in the bikes master cylinder, but prevents fluid loss directly from the master cylinder vent due to the crazy angles the shallow master cylinder is put through whilst riding the bike. To check or top it up, you have to turn the steering to level each cylinder.

[drewbie]

I think the seal is just that, so that it can be sold as a sealed for life part and kept in store without the risk of fliud leaking from it. I removed and replaced it with an 'o' ring, i bleed thru new fluid yearly using a pressure bleeder and keep the level 10mm below the top of the reservoir using a simple dipstick made from a bit of wire. This clean fluid i believe helps protect the seals in both the slave and master from faliure.

[COLVERT]

I think the seal is just that, so that it can be sold as a sealed for life part and kept in store without the risk of fliud leaking from it. I removed and replaced it with an 'o' ring, i bleed thru new fluid yearly using a pressure bleeder and keep the level 10mm below the top of the reservoir using a simple dipstick made from a bit of wire. This clean fluid i believe helps protect the seals in both the slave and master from faliure.

Clean fluid sounds like a good idea but may I ask you a question ??
Changing the fluid presupposes that the old fluid is dirty.
If it is dirty then where did the dirt come from in a sealed system ?
I guess the only place could be the seals wearing away.
If this is so then changing the fluid will not make the seals new again, just clean and worn. Clean fluid will leak past worn seals just as easily dirty fluid !!!
I think having to perform that contortionist act to replace the old fluid will afford very little gain and a great deal of sprain !! Lol.

:shrug::shrug::shrug::D:D


Colvert.

[COLVERT]

I have been told that the clutch reservoir cap has a vent hole in it. I'm slightly surprised, because I have always assumed that the internal 'condom' gizmo was to allow the fluid to maintain its equilibrium pressure by allowing the condom to expand and contract. If that's not the case, and the cap does indeed have a vent hole, then why on Earth did they fit it?

TC
T-Cut, Sir. Not having actually seen one of these gizmos, could you tell me if it is actually sealed with a volume of air inside it ??
If so then I think the way you described it's function is correct.


Colvert.
:bowdown:

[Phil]

The condom type thing is there to allow the fluid to rise and fall. It also completely seals the fluid from air. The cap has a hole in it to allow the expansion and retraction of the condom.
At least that's what I thought but Harry has other experience. :)

[drewbie]

Clean fluid sounds like a good idea but may I ask you a question ??
Changing the fluid presupposes that the old fluid is dirty.
If it is dirty then where did the dirt come from in a sealed system ?
I guess the only place could be the seals wearing away.
If this is so then changing the fluid will not make the seals new again, just clean and worn. Clean fluid will leak past worn seals just as easily dirty fluid !!!
I think having to perform that contortionist act to replace the old fluid will afford very little gain and a great deal of sprain !! Lol.

:shrug::shrug::shrug::D:D


Colvert.

The blackening of the fluid is mainly caused by the reaction of the fluid with aluminum. Best to use a brand name of dot 4.

[FrenchMike]

Hi,

You want to know why black dirt:

Here the state of my slave seal after 70 Kmiles

6543

Mike

[T-Cut]

Indeed, the black contamination typically found in old fluid is rubber particles from the pressure seal on the piston. The relatively short life of these units is definitely associated with deterioration of the seal material. One might argue that flushing the debris away using a new fluid charge on a regular basis can only improve its chances of a longer service life.

TC

[HarryM1BYT]

The condom type thing is there to allow the fluid to rise and fall. It also completely seals the fluid from air. The cap has a hole in it to allow the expansion and retraction of the condom.
At least that's what I thought but Harry has other experience. :)

No, No....

I was suggesting that there MUST be an air vent in the lid to allow for expansion and contraction. I said 'Every hydraulic system has to have some sort of vent in the master cylinder, above the level of the fluid. Large commercial/ industrial hydraulic units have a vent often sealed with a drying filter.'

I said 'The top of the 75's brake master cylinder has a vent in it, to allow air in surely? If it didn't, then as the brake pads wore down the fluid in the cylinder would be under a slight vacuum.'

T-Cut suggested he hadn't realised it was vented.

Phil said 'Hi, I am more than likely wrong but I can't think of any brake or clutch circuit with a vent to the atmosphere on any model? :o '

[T-Cut]

The cap vent is primarily to allow air to replace the displaced fluid volume during the pressure cycle. As the slave piston returns, the volume of fluid in the reservoir recovers and air then leaves the headspace. The brake master cylinder is similarly vented. If the clutch reservoir condom is indeed a flexible diaphragm (which seems unlikely from what I've seen), then the fluid level fall/rise would be balanced by an inflation/deflation of the diaphragm without need of a vent. However, I believe (from what I've read) that the condom is of rigid plastic construction, so it's purpose remains a mystery (to me anyway). Maybe my undertanding of its construction is wrong?

TC

[Phil]

I will post some pics in a minute..

[Phil]

As promised..
http://i841.photobucket.com/albums/zz336/Sweepthedog/photo.jpg
http://i841.photobucket.com/albums/zz336/Sweepthedog/photo2.jpg
http://i841.photobucket.com/albums/zz336/Sweepthedog/photo3.jpg

[HarryM1BYT]

The diaphram/condom thingummy is very flexible. As you can see from the photos, with the condom in place it takes up a lot of room in the cylinder, it does no leave very much room fluid - most of the fluid is displaced as the condom is put back into the cylinder. I spent ages trying to work out how to refit the condom in a compressed form, so that it wouldn't displace so much fluid - in the end I gave up and simply cut the condom down.

I think, simply fitting something (a disc) a touch smaller than the internal diameter of the cylinder, which would float on the fluid - would be as good a method of preventing moisture absorbtion from the air. The less surface area between the interface between fluid and air, the slower will be the moisture absorbtion.

[T-Cut]

The diaphram/condom thingummy is very flexible.


Ah, thank you. That explains everything. The condom inflates with air coming in through the vent. It deflates in reverse fashion. However, the fluid is sealed from atmosphere by the upper rim of the condom which is compressed by the cap.

IMO, the condom is more trouble than it's worth, especially if you are prepared to do a clutch fluid replacement as per the brakes schedule. That would make sense, especially if you have a flexible back. I'd like to make the clutch reservoir extend to somewhere accessible under the bonnet so you could refill it without trying to be Houdini every two years. It would be easy enough as per my draft below.

http://i5.photobucket.com/albums/y191/waveguide/Clutch_Stuff/My_Modified_clutch_Hydraulics_SMALL.jpg

This principle has been discussed several times here and there but I don't think anyone's actually gone and done it yet. I just wish I had a flexible back. Another eBay business eh?

TC

[COLVERT]

The diaphram/condom thingummy is very flexible. As you can see from the photos, with the condom in place it takes up a lot of room in the cylinder, it does no leave very much room fluid - most of the fluid is displaced as the condom is put back into the cylinder. I spent ages trying to work out how to refit the condom in a compressed form, so that it wouldn't displace so much fluid - in the end I gave up and simply cut the condom down.

I think, simply fitting something (a disc) a touch smaller than the internal diameter of the cylinder, which would float on the fluid - would be as good a method of preventing moisture absorbtion from the air. The less surface area between the interface between fluid and air, the slower will be the moisture absorbtion.
Thank you for the info. which I found interesting. Just one thing though. Why are you concerned about moisture being absorbed into the fluid ??
There is no danger of it boiling, as in a brake caliper and as it is incompressible it will work just as well as brake fluid !!!
If it didn't cause rust you could operate the clutch with water as the energy transfer agent.


Colvert. :getmecoat::):):)

[T-Cut]

I think, simply fitting something (a disc) a touch smaller than the internal diameter of the cylinder, which would float on the fluid - would be as good a method of preventing moisture absorbtion from the air. The less surface area between the interface between fluid and air, the slower will be the moisture absorbtion.

Frankly, this idea that hydraulic fluid sucks moisture from the atmosphere is grossly exaggerated. Many, many brake and clutch systems NEVER get replenished and they manage to keep going. The condom is all part of MGR's sealed for life principle, which is, frankly, a joke. Far better to have a clutch fluid replacement schedule along with the brakes. (2 years/30K miles). The only issue with that is actually doing the service. That's why I invented the above system for fluid changing. Of course, none of it matters that much if the master and slave seals aren't up to it. And of course, the slave is the fly in the ointment.

TC

[HarryM1BYT]

I am not concerned about it boiling, my concern is with regards to the damage to the system, that the moisture on the fluid could do.

[COLVERT]

Ah, thank you. That explains everything. The condom inflates with air coming in through the vent. It deflates in reverse fashion. However, the fluid is sealed from atmosphere by the upper rim of the condom which is compressed by the cap.

IMO, the condom is more trouble than it's worth, especially if you are prepared to do a clutch fluid replacement as per the brakes schedule. That would make sense, especially if you have a flexible back. I'd like to make the clutch reservoir extend to somewhere accessible under the bonnet so you could refill it without trying to be Houdini every two years. It would be easy enough as per my draft below.

http://i5.photobucket.com/albums/y191/waveguide/Clutch_Stuff/My_Modified_clutch_Hydraulics_SMALL.jpg

This principle has been discussed several times here and there but I don't think anyone's actually gone and done it yet. I just wish I had a flexible back. Another eBay business eh?

TC
That is a great idea T-Cut and worth some thought.

When the clutch hydraulics fail it seems the usual culprit is the slave cylinder disintergrating. This is frequently followed, not long after, by the master cylinder, which one supposes has done the same amount of work.
( But under less arduous conditions. )
There seems to be in most cases a gradual loss of pedal. This indicates worn cylinder rubbers. By the time things have reached this state is there really much use in prolonging the agony by topping up the master cylinder ? :shrug:

Colvert. :confused:

[T-Cut]

I am not concerned about it boiling, my concern is with regards to the damage to the system, that the moisture on the fluid could do.


I think you're worrying unnecessarily. The percentage of water absorbed by clutch hydraulic fluid open to the atmosphere (vented cap) is minute. The hydraulic system is designed to operate with a hygroscopic fluid (absorbs moisture) and will tolerate any miniscule concentrations of moisture likely to be absorbed during the typical life of a clutch system. And it's standard practice to renew the hydraulic system when the clutch itself is overhauled.

TC

[COLVERT]

I am not concerned about it boiling, my concern is with regards to the damage to the system, that the moisture on the fluid could do.


I am not being contentious in any way but is there ANY hard evidence that the contributary factor in clutch hydraulic failure to be caused by water ingress ?? :shrug:

Colvert.

Has anybody performed a post mortem on a master cylinder to see if there is any rust or pitting present ? :shrug: Anybody ?????

[T-Cut]

When the clutch hydraulics fail it seems the usual culprit is the slave cylinder disintergrating.

That can be fixed more satisfactorily by fitting the significantly cheaper Freelander diesel slave cylinder. It's of a more robust construction and fits all 75/ZT models. Minor adjustment of the hydraulic pipes (which are in steel) may be necessary, but this should put the slave problem to bed.

TC

[Mike V]

That can be fixed more satisfactorily by fitting the significantly cheaper Freelander diesel slave cylinder. It's of a more robust construction and fits all 75/ZT models. Minor adjustment of the hydraulic pipes (which are in steel) may be necessary, but this should put the slave problem to bed.

TC


is that worth commiting to the memory banks TC?

''If your slave ever goes replace it with a Freelander item''

I have seen it mentioned once or twice around the forums.

[T-Cut]

is that worth commiting to the memory banks TC?


It'll save at least 50% of the parts cost and probably last 'forever'.

TC

[descam]

I am not concerned about it boiling, my concern is with regards to the damage to the system, that the moisture on the fluid could do.



My concern is freezing. Last week the temperature was -5 celcius en I noticed my clutch slipping above 3rd gear when I accelarate hard.

Now it not freezing anymore (+3 celcius) en my clutch doesn't slip anymore.

Replacing the fluid should do the trick?

[chris75]

That can be fixed more satisfactorily by fitting the significantly cheaper Freelander diesel slave cylinder. It's of a more robust construction and fits all 75/ZT models. Minor adjustment of the hydraulic pipes (which are in steel) may be necessary, but this should put the slave problem to bed.

TC

Just harking back to this quote , can T-Cut or anyone who has done it advise just what "adjustment" is required to the pipe ? Definitely seems the way to go :xmas-smiley-031:

[Greeners]

My concern is freezing. Last week the temperature was -5 celcius en I noticed my clutch slipping above 3rd gear when I accelarate hard.

Now it not freezing anymore (+3 celcius) en my clutch doesn't slip anymore.

Replacing the fluid should do the trick?

Clutch fluid is hydroscopic, and over a period of time can absorb moisture. It certainly wouldn't hurt to change the fluid. Nip down the pound shop and get a turkey baster and a short length of plastic tube to fill the master cylinder,

[T-Cut]

Just harking back to this quote , can T-Cut or anyone who has done it advise just what "adjustment" is required to the pipe ? Definitely seems the way to go :xmas-smiley-031:

The Freelander diesel slave cylinder will fit all 75/ZT models, both diesel and petrol. The hydraulic pipes are metal as distinct from plastic and will have a slightly different shape to accomodate the Freelander engine space. However, they are near enough apparently to go in with relatively little adjustment. They have the same self-seal coupling as the OEM system.

TC

[T-Cut]

My concern is freezing. Last week the temperature was -5 celcius en I noticed my clutch slipping above 3rd gear when I accelarate hard. Now it not freezing anymore (+3 celcius) en my clutch doesn't slip anymore. Replacing the fluid should do the trick?

The very cold weather affects almost everything mechanical on a car. However, the hydraulic fluid will never freeze due to moisture absorption. DOT4 is made from glycols similar to antifreeze. As we know, a 50/50 coolant mix is good down to -40C. I think it would take a few hundred years for DOT4 to absorb that much moisture. In a very old system, decades old, the moisture will still be less than ten percent. It certainly won't freeze in the UK. However, I believe the clutch fluid should have a similar service schedule to the brakes. Replace every 4 years.

TC