Hydraulic clutch problems?
 

Hi all, I have a problem with my hydraulic clutch which i thought was a leaking slave cylinder so I bought a new one but this has not solved the issue!

When I push the pedal to blead the system (bleed pipe on the other end going into container full of fluid) the master level drops as it should and clutch fluid comes out the other end as it should.

I have put through approx 3 litres with no air coming out what so ever but the pedal remains limp and will not work the clutch.

I have double checked the 3 connections with no leaks and am at a loss as to the problem?

Does it matter in which position the clutch control arm is when bleeding?

The clutch was working before engine came out and has only covered 20k but the control arm can be moved anyway manually.

Has anyone got any ideas as to the problem or am I doing something wrong?

Cheers
Craig

Craig, are you pressing the pedal with the nipple open, then whilst holding the pedal down, closing the bleed nipple, then repeating the process?

No.............I take it that is the problem?

Wish I was not at work in an hour I would try that now will try tomorrow John and let you know cheers

Craig

I have just thought about this for a couple of minutes and now feel decidedly stupid.... I don't know how I expected the system to pressurize by just pumping through liquid :icon_rolleyes:

Hi Craig.

When you move the clutch arm, you should be able to move the clutch arm on the gearbox up to a certain point. then you will feel like you need super man to move any further. This is the clutch engaging.

And don't forget. Keep the master cylinder topped up.

Craig, I did mine as I described - seems to work okay.

Right this fracking clutch is now really starting to piss me off!

I have now spent about 25hrs on this thing including all day today and it's still not working.

I have had it to bits so many times and today managed to get a slight feel to the pedal for the first time enough to move the clutch fork about 4mm when pressed but not enough....

does anyone have any ideas??????????????

what I can say is that there is a new slave on there and the master cylinder when pedal pressed whilst bleeding will empty the fluid in three presses so it must be shifting enough fliud

Craig

Craig

Just a thought, as I have had this issue when bleeding brakes, is the car level, not trying to apear insulting but sometime the simplest things can help.

Is it worth contacting you local Honda dealer if there are any secrets they can offer.


Steve

Cheers Steve, no it's not insulting I am sure it is something very simple like that but just can't get it, yes car is level and I have tried unbolting the master cylinder and lowering it below lines to see if this makes a differance but it did not.

I'm not even sure why the clutch has got a bit firmer today and I can't help thinking that somewhere there is either an air pocket or a leak but no fluid is leaking from the 3 connectors

Hi Craig.

Been there done it with the Rover Clutch. I the Rover clutch are known to be barstewerds to bleed. Especially the 600 TI which I learned how to do it.

This is the way I did it.

Three people to start off with.

Top up reservoir fully. Check and top up during process when necessary.

Get assistant to sit in car.

Put clear plastic tube onto bleed nipple on slave cylinder and end into glass jar.

Open up bleed screw and ask assistant to depress clutch pedal fully ~ by hand is best at this stage ~ pedal may plop to floor quickly and stay there ~ that can be normal. Leave it there. Close bleed screw.

Ask assistant to raise clutch pedal fully and hold there.

Open slave bleed nipple.

Ask assistant to depress pedal fully and hold down.

Close bleed nipple.

Raise pedal and hold.

Open nipple.

Depress pedal.

Close nipple.

Repeat this process untill bubbleless fluid appears in tube/jar. May need to do this ten times ~ maybe less ~ depending how much air allowed into system when it ran dry.

Then open nipple one more time and push pedal to floor AND HOLD IT THERE!

Close nipple immediately with pedal still flat on floor.

Change of process now. Still under car, open slave cylinder bleed nipple and push in slave's push-rod as far as you can and hold it there. This will expell any air out of the SLAVE cylinder ~ lock nipple and relase push rod which should return in a second or so. You can push the push rod into the slave by hand easily with the nipple open. Don't forget to top up reservoir as this process will use quite a lot of fluid through the sytem.

Open nipple and push the push rod into slave as far as you can, hold it there and close nipple, repeat a couple more times observing clear fluid into tube ~ ideally no bubbles now. Check nipple firmly closed.

Then get a length of wood say 2 by 1" or better still a tube about 20" long ~ as used with small hydraulic jack handles works well.
No need for the assistant inside the car now except to observe the pedal ~ still on the floor. The next operation should return the clutch pedal to the fully raised position so that it stays there!

Place the wood or tube in such a way that you can use it to lever carefully and slowly the push rod into the slave cylinder ~ only this time with the bleed nipple still locked shut NOT open. As you do this, provided you have expelled all the air from the sytem as described above, you should hear the clutch pedal return to the fully up position WITHOUT assistance as your pushing fluid back up the system towards the master cylinder. This process usually will make a 'clunk' inside the car as it does so. If it does, you know you've sorted it and you can relax the leverage pressure on the slave push rod so that it returns.

Select neutral and start car. Depress clutch and select various gears to check operation.

Did that last weekend. My son since reports that the clutch and gear operation on his car is better than at any time before.... Sorted.

And a Rover 800 guy:

Get a jar, few metres of rubber tubing.
Make two holes in the lid for the rubber tubing.
One length of tube goes from caliper bleeder to jar.
Other length goes from vacuum outlet on the inlet manifold into the jar.

Start the engine and you've got a vacuum pump.
Open or close the lid or close the bleed nipple to control the fluid input/output.

Dont let the tube from inlet manifold dip into the brake fluid or it'll go into the engine, shouldn't cause any damage anyway, just clouds of white smoke as it gets burnt.

I used a coffee jar, drilled two holes etc, keep the cardboard bit from the lid or it won't seal.
5 mitres of clear 5 mill tubing from Focus, less than a fiver.
Needs to be a glass or metal jar or it'll just collapse before you generate enough vacuum to suck the fluid out.
I'm surprised how much vacuum a 2 litre car can generate actually.

You will get the odd splash of fluid up the vacuum pipe, as long as you don't let the fluid get to the same level as the vacuum pipe you wont have a problem.

Used less than 500 ml to bleed a Rover 800, I've now got almost a whole gallon of Dot4 sitting in the cupboard, looks like I'll be bleeding every car I can find to finish off what's left.

Hope this helps.

Hi John, thanks for your reply good post but unfortunately I had already done all of the above except push in the slave cylinder and I have done that tonight but no differance.............

My pedal is not actually soft about the same as my clutch pedal on my astra td and the clutch fork does move about 4mm but I am now 100% certain that I have covered all the possible probs so am at a loss what to do??

I can either rip it out and put cable in which would mean a new pedal box or I can get a mechanic to have a look but but I fear this would do no good!

I am sure this will pass but at the moment I feel like leaving the piece of shit well alone to rot.

Many thanks guys for the advice though it's appreciated

Craig

What system are you using?

He's using a honda master and slave.

Oh. Probably no help at all then. I was going to say that Rover have a valve of sort part way down the pipe. Don't know how important this is.

The really odd thing is that my identical setup (master and slave) was bled in a spare 5 minutes, and seems to work fine. :noidea:

Well I ordered a new master clutch cylinder the other day to see if this improves things, that will mean all new parts fitted now!!

I pick it up in the morning so hope to have it fitted tomorrow night

Craig

Last week before you posted this I did start to wonder about a restricted flow valve or a checked one way valve but alas apparently there is not on the honda

One brand new slave cylinder, master cylinder and all new o-rings later and..................no differance infact the fork moves less with the new master on than the old one!

Nothing left to try

Hi Craig.

I have no valve in my system.

OK things to try:

Make sure the clutch and lever are ok. You will have to get a measurement off one of the other honda guys of how much the slave lever moves to engage clutch. Then try it by hand. As it gets stiff (this is the clutch engaging) you might need help levering it further.

When you tried the above, what were the bubbles doing in the clear tube at the slave when the pedal was being pressed? Going towards the jar or back towards the master cylinder? I know the above is a long winded process with the dancing of feet and spanner at either end, but found that's the only way that works. Not tried the vac bleed but heard it's works great.

I wish I was closer otherwise I would give you a hand.

Craig,

There must be something, that all of us have overlooked.

If the system is hydraulically sound, and it has to be given new components, and no leaks, then it'd be handy if you could post pictures of your system from pedal to slave cylinder.

As for master cylinder stroke, the full travel of my clutch pedal translates to about 95 % of the master cylinder stroke. The Clutch starts to bite about 40% of the way up the pedal stroke. The action is quite digital, as the pedal is quite short (about 60% of the honda clutch pedal length at a guess).

John.

Right here goes, John the bubbles go towards the jar when pedal pressed!
some photos in order from front to back of car

Pic of reservoir and master cylinder
http://i157.photobucket.com/albums/t...y/DSC00574.jpg

Close up of master cylinder
http://i157.photobucket.com/albums/t...y/DSC00568.jpg

Pic of inside the car clevis and master piston
http://i157.photobucket.com/albums/t...y/DSC00571.jpg

pic of pedal in place
http://i157.photobucket.com/albums/t...y/DSC00580.jpg

exiting the rear bulk head
http://i157.photobucket.com/albums/t...y/DSC00582.jpg

entering the slave
http://i157.photobucket.com/albums/t...y/DSC00585.jpg

when pedal pressed equates to 100% piston travel

clutch
 

Hi Craig,
haven't been checking forum for a while, mega busy at work. Sorry to hear your problems with clutch. Is it possible your bulkhead structure is flexing too much and thus losing travel at the slave cylinder. I presume the clutch doesn't clear when fully depressed, does the pedal feel really sloppy which would be hydraulic problem or does it feel normal and just can't get gears.
If the latter the clutch plate may have stuck to the flywheel due to not being used for a long time. Ring me if you want to discuss.
good luck with it anyway.
Brian
ps apart from clutch hows it going

Hi Brian, thought I would have seen you at stoneleigh with your updated car?
I will have to come down and have a look soon.

Bulkhead does not flex as it's reinforced with 3mm stainless top to bottom.
pedal has feel and master piston travels 100% with pedal pressed which in turn moves the clutch fork about 1cm maybe a bit more but after speaking to John and Jerry my pedal is not stiff enough

Although I have spent about 35-40 hrs on it now and put through about 5 litres of fluid I still think it's hydraulic and not the clutch

Just not sure how to combat it now may take you up on the call.

Other than that the car is ready to drive
Craig

Hi
What size hose are you using to go front-rear?

Hi Craig.

The bubble direction says to me the master is doing it's job.

Grant has a good point. I'm using copper pipe complete from end to end. Pirtek suppplied the pipe and put the ends of the master and slave on for me.

I found that brake pipe is larger than the clutch pipe in diameter.

I have questioned this in my own head as the clutch hose is goodridge front to back about 8mm internal which was made up by pirtek but after speaking to John (alackofspeed) last night the internal dia does not make any differance (lost me abit then but something about equazi pressure) so that is something else struck of my list of things it could be!!

Infact just realised that I no longer have a list........:icon_frown:

Hi Craig.

When Ian (Merlinman) did his hydrualic clutch (building a 5EXI with old DOHC honda lump), changing the copper pipe diameter made all the difference.

clutch
 

Hi Craig,
I think Limpabit might have hit the nail on the head. If you are using large bore pipe the pressure will be the same but the distance travelled by the slave cylinder will be less, not sure about this as I'm no hydraulic engineer but you might have to try it as you have nothing else left on your list mate.
I couldn't make Stoneleigh due to heavy work schedule, the cars doing well though, gearchange is superb to what it was. I have loads of jobs to do still when I get some spare time. I use the car every day for work and so far have had few problems but it is only 4 miles away, I haven't done any long runs in it for a while.
Hope you get sorted with your clutch soon, if you want to try solid brake pipe I can make one up for you, I am using solid brake cunifer pipe on my clutch by the way.
Brian

The hydraulic pipe diameter should make no difference, if it is assumed that the fluid is incompressible, and the pipe's volume is unaffected by internal pressure.

Looking at it very modularly, the fluid leaves the master cylinder, is displaced into the tube, which in turn displaces the slave cylinder's piston.

The only way I can see the larger bore pipe making a difference, is if the pipe, because of its greater diameter, expands sufficiently under pressure, that it "consumes" some of the fluid displaced by the master cylinder, thus reducing the movement of slave piston.

Craig, my point about the system, is that it is qausi static, and that flow speed can be ignored. It's not like fuel hose, for example, were there is a pressure drop resulting from the flow, hence it being advisable to measure, and regulate fuel line pressure as close to the point of use as possible.

Gent's if you are talking about pressure in lines or pipes etc, then pipe internal diameter has a massive effect. It is down to internal friction of the material on the internal walls of the pipe or tube. Bigger diameter less friction for the increase of fluid moved.
I work in an industry where amongst other things our equipment is used to supply paint around the car factories. Too small a pipe diameter and the pressure drops are horrendous. Resulting in too little paint pressure at the robot sprayer electrostatic atomisers.

If you want to compute the pressure diiference in pipes then take a look at the following:
http://www.flowmaster.com/solutionov...FQNQEgodHw--6g

Or failing that do a google on Pressure Drop Calculations.

Now one thing that does not change (if you alter the diameter of pipe work) is the amount of travel. So the travel will be the same it's just that you will be exerting less pressure if the pipework is too small.

Cheers Mike

Mike, your comment about pressure was what I was getting at in my post above. I was taking the flow out of the equation, stating that a clutch hydraulic system is quasi static, and thus the flow speed can be ignored - the only issue is static pressure of the fluid, and thus pressure drop associated with pipe bore, and fluid velocity and viscosity does not need to be considered.

Anyhow, the jist of the matter as far as Craig is concerned, is that my clutch works using a narrower bore similarly constructed flexible tube, and the same specification master and slave cylinders. We can therefore rule out the diameter of Craig's clutch hose being the cause of his difficulties.

Next suggestion what might be wrong..........? (I'm clean out of ideas, having discussed this to death on msn with Craig.)

The line pressure drop due to flow is only an issue during pedal movement - I agree with John that if you just consider the static cases at each end of the pedal motion then you can ignore the bore size. The only potential issue I can see from small bore would be that the clutch movement may be too "damped" - i.e when you release the clutch pedal it might return more slowly than you want due to losses in the pipe. I've gone with 6mm copper which is as per honda use on the type R I think? (except the small bore section over the transmission). I'm not talking from experience yet though because I haven't filled my clutch system yet!

On the subject of which - what's the total travel required at the master or slave cylinder to disengage? John - I saw you said you'd got 95% of the master cylinder travel available: does it need all that? I fear my setup currently has less.

Richard

Rich, I can't recall what bore my goodridge tubing is, but I think it's 3/16 - my friend is in the bespoke tubing business, and what I have is standard issue brake / clutch hose. Whatever size the hose might be, one thing is for sure, there are no problems with the bore damping the flow. When you bleed the system you'll see how small a quantity of fluid is displaced with each pedal stroke, hence the inconsequential effect of any dynamic losses in the system.

When I said 95% that wasn't totally accurate, and is just my best guess from what I recall when I built my rather odd clutch system. I know that 100% pedal stroke is very close to being 100% of the master cylinder's stroke.

I would say my clutch starts to bite around 35-40% of the stroke above the fully depressed position, and is fully engaged around 65% of the travel. I've not measured it though, and the figures are just my best interpretation of what I feel through my foot!

What is the case with my setup, is that with the lever ratios compromised to suit the pedal length needed in the Marlin, the clutch is quite sharp when compared to typical modern cars.

Rich, have you gone for straight copper, of cunifer? I don't know what the SVA requirements are, but I was lead to believe a few years back, that cunifer should be used instead of copper as it's less likely to degrade in the presence of brake fluid.

I remeber now. Your right. Make the pipe larger helped with the foot effort not the actual movement.

Did you try moving the clutch lever on the box to see if you can engage the clutch by hand?

I had it as said above. Due to the clutch not being used, it got stuck. I manged to free it up by raising the rear wheels off the ground. Run the engine in a high gear and hit the brakes.

The only other way is remove the box.:(

Might be worth asking one of the other guys to measure the clutch arm movement on the box when the pedal is pressed. That way you can see if you have this amount of movement by hand.

Hi John, yeah the fork seems to move freely but very difficult to push fully with engine in car

Hi
We switched the pipe on John (Marlinturbo)'s 5EXi from 0.19 to 0.13" ID and it got us the travel and pedal feel required.
I don't know (or care much) about all the theory... But it worked!

Grant, chhers for that!

I will defo try this then as it sort of goes against everything that has been said but the clutch line is the only part I have not tried changing and I know there is no air in my line for defo......

Spent about 70hrs on the bitch now!!

Craig

I will let everyone know the outcome

I agree it's odd... But there was deffo no air in John's line.
In desperation we changed the pipe and hey presto... Clutch!

Any joy yet Craig?

Not intending to gloat if not, but I thought I'd explain my clutch experience following today's efforts, just in case it helps.

My setup:

- Civic R master cylinder linked to Rover clutch pedal. Before trying to fill with fluid I modified the cyclinder mounting with a spacer to shift it 5mm forwards -this followed various bits of advice (thanks chaps) suggesting I should make sure I had the whole master cylinder travel available. Now gives full cylinder travel for full pedal travel. Master directly connected to 6mm copper hard line through tunnel to a bulkhead fitting at the firewall. 5mm braided flexi from there to slave cylinder.

Got to be honest - bleeding was a piece of cake. I filled the reservoir and pumped the master a few times with no real effect. Then I opened the slave bleed a couple of turns and stuck a long length of clear hose onto the nipple. This was long enough for me to stick the end in my mouth while still topping up the reservoir. I sucked (hard!) until fluid without bubbles was coming up the tube (then stopped before getting a mouth full!). I then tightened the bleed nipple again and hey presto, clutch works, fully disengages (heavy but I I haven't any more pedal travel to play with so tough). Took about 5 minutes. I really can't think what the problem is at your end. Must be hugely frustrating :eusa_think:
Richard

PS - yes, I used straight copper, not cunifer. As far as I'm aware there's no issue with corrosion from brake fluid. After all, pure copper brake line is readily available. Hope this isn't an SVA issue... I guess for SVA purposes it's cunifer anyway just to be on the safe side :nod:

Hi all, Update on my piece of shit clutch!!

After changing all my components and spending £££'s my clutch still did not work and I was basically wanting to smash my car into little bits.....

I have spent over 70hrs on it in total maybe slightly more.

I decided a couple of weeks ago to take everything off and down to a local garage who pressure bled the system for me.....garaunteed no air my hopes were high!

Connected everything back up and hey presto.....it was no better still not working.....ffs

After it playing on my mind for a while and a few people posted on here about the id of the clutch line I visited pirtek and asked there advice.
They told me the inner dia should not make a differance but sometimes it can but they could not make me up a line smaller then the goodridge I already had.

Anyway visited Brians garage on fri (holgate 86) who very very kindly made me up a line thanks much........

Just had the time to fit it tonight due to work commitments and if being honest not expecting much.

connected it up did the usual with bleeding it took the normal 5 mins and clutch works like a dream...........I can select all gears and little drive followed works perfect.

So after all the wasted time it was definately the innternal dia of clutch line, just wish I had followed my instincts and tried it earlier but you live and learn.

My car would bhave been more or less done now but at least I can get motivated again.

Many thanks to everyone for posting and offering advice it is much appreciated

Craig

Great news! I'll be b*ggered if I know why it has made a difference.... the *only* logical explanation can be the length of pipe, and the wall elasticity.