Outer Limits 4x4 Board

RAY185 wrote:Andy, when the clutch actually works, how far on the pedal does the clutch disengange? Towards the top, around the middle or pretty much flat to the floor?

i reckon its got 3 distinct levels
a) 1st press = no clutch, change gears
b) 2-3 presses = just enough to change gears, only need to get off the clutch a mm and your in gear (more noticable when engine is cold/1st drive of the day)
c) 3-4 you have about 1/3 off the floor and the clutch works like it would normally

once i find this level (c).. i just make sure my foot doesn't lift off completely otherwise its goes back to level a.. and i need a few solid pumps to get it back..

shorty_f0rty wrote:

RAY185 wrote:Andy, when the clutch actually works, how far on the pedal does the clutch disengange? Towards the top, around the middle or pretty much flat to the floor?

i reckon its got 3 distinct levels
a) 1st press = no clutch, change gears
b) 2-3 presses = just enough to change gears, only need to get off the clutch a mm and your in gear (more noticable when engine is cold/1st drive of the day)
c) 3-4 you have about 1/3 off the floor and the clutch works like it would normally

once i find this level (c).. i just make sure my foot doesn't lift off completely otherwise its goes back to level a.. and i need a few solid pumps to get it back..

Has to be the master cylinder then

Sounds like the check valve is sticking or something but pumping the peddle forces it to close, take foot off completely check valve opens, and probly sticks open again.

But you say the master works fine in the other vehicle, and that is what's perplexing.

to clarify..
- busted seal on slave clutch cylinder
- replace busted slave with spare slave (off parts vehicle, with working clutch)
- current issue was experienced, swapped in new slave cylinder
- swapped in spare master, still issue
- swapped in spare slave, same issue.. replaced new slave
- pumped at least 500mls of dot4 brake fluid through it each time new part added
- swapped in new master, same issue
- fixes itself after some wheeling (after approx 150 hwy km's)
- issue comes back after 2wks of easy daily driving. (approx 300 daily kms)
- replace spare slave and master cylinders on the parts vehicle, bleed once and clutch works perfectly no issues as on DD.
- bled clutch from master and from slave
- thread taped the nipple on the slave
- no fluid loss at all
- ARGH!

ok, the only viable solution is hardcore wheeling weekly.

Take the master cyld apart, and make sure you dont have some gunk in the valving in the front of the piston area, you will have to take out the circlip, and tap the piston out.
Once its out, just make sure that there is no damage to it, or that its been assembled correctly.
Bleed on the bench, then fit and bleed system.
Make sure your getting pedal movement corresponding at the same time on the clutch slave cyld assy.

Just to clarify, the new parts are the correct ones, and correct internal diameter for the vehicle you currently have them on??
If they worked on another, but not on this, is there a difference between them.

Different internal bores will give different pedal pressure, and different throw distance at the slave.

Trains

edited to add
I remember having a wierd problem with a brake master, simmilar to a clutch master, as it was on a formula ford.
when we bled it after assembly, it was fine,and good pedal pressure, but once on the track, and running, the pedal would go right to the floor.
We took it apart, and it had no visible sign of damage, or poor assembly etc.
Ended up just throwing it out,and getting another one, as it was new off the shelf when we fitted it, but when racing, no front brakes.....
go figure.

Trains

You can measure the movement on the fork ( slave conected side ) when the issue it's present and when not .?

Just to see if it varies ..

I thought other option could be the head .. the heat affect the DOT3 quality if you run the headers or exhasut to close to the master or slave ( clutch line ?)

Trains,

thanks for the tips, although with whats involved i dont think i'll get to dissassemble the master for a while. just the fact that the issue occurs for both the new and the spare master leads me to believe that its not worth the effort at this stage.

the bit im confused about is the fact that the original master cylinder (didnt show any signs of leaks), the spare master and a new master cylinder show all the same symptoms (having replaced just the slave with a spare & new slave cylinder).

The spare parts ARE the right one as far as Sunshine State 4wd are concerned and it all bolts up ok.

The slave does move when pressed. i noticed while getting the missus to help bleed the system that the first press with no pedal presure would result in a tiny movement at the slave, and following presses would move the slave more until there was enough pressure to move it fully.

my mechanic seems to think the clutch is going to need replacing soon as he said he can see there is not much meat left on the place through the clutch fork hole..

i haven't noticed any clutch slipping at all and was under the impression from the previous owner that the clutch only had 10,000km's on it..

would a worn clutch produce these sort of pedal pressure issues?

Andy. When you fitted the new clutch slave it would have come with a new adjusting rod, it goes between the slave and the clutch fork. I think this might be your problem. Check and see how much freeplay the clutch fork has, it should be about 5mm at the most. Try adjusting the rod out a bit further. If its not adjusted out enough it will give the symptoms you're talking about.

Not sure if the diesel clutch slave is a similar setup to the petrol but if it is then it might be worth looking into.

shorty_f0rty wrote:my mechanic seems to think the clutch is going to need replacing soon as he said he can see there is not much meat left on the place through the clutch fork hole..

i haven't noticed any clutch slipping at all and was under the impression from the previous owner that the clutch only had 10,000km's on it..

would a worn clutch produce these sort of pedal pressure issues?

I would not do the clutch untill it starts to show signs of slipping.

No a worn clutch would not show these signs.
What you are experiencing is a lack of disengagement, which by all accounts seems to be related to the hydraulic side of things.
Even with a broken diaphragm spring in the pressure plate assy, it would give different symptoms to what you have described.

My money is that there is a different internal diameter in the master, thus giving you less travel at the slave.

It is not a big deal totake the m/cyld apart and have a look, dont think you wont get it back together, there pretty simple, just be carefull and think when you put the piston seal back in, so you dont damage it.

Ok thinking cap on.
Start at the beginning.
Sorry if we go over stuff already done, but can you go through these, and let us know the results of each test please.

If you clamp off the flexible hose with some pliers, or proper hose clamps for this purpose, do you have a firm pedal with no travel??
If its still spongey, the problem is air in either the mcyld or the line to the hose that is clamped.

Does the firewall have a crack in it, thus the clutch m/cyld moves when the pedal is depressed, resulting in loss of pedal sweep.

Are the pedal pushrods the same length as the original.

Does the flexible rubber hose bulge when the clutch is depressed?

Is the slave cyld piston pushed as far back into the slave cyld as it can go, and then adjusted up the pushrod length so there is just 1-2mm of freeplay, if at all.

By what you describe, the pedal travel, thus the m/cyld piston travel, is not matched by the slave cyld piston, thus the throw out fork is not being moved as it should.

Did you bleed the mcyld on the bench first,

Put in vice, fill with fluid

Press in the piston all the way, place thumb/ finger over outlet hole,and let the piston slowly return,

do this till you get firm pressure in the mcyld, then, and only then, add it to the system, and bleed from the slave.

I would suggest using some flat tooth pliers, or vice grips on the flexible hose, and gently close the pliers after the pedal has been pushed to the floor, then telling the person in the cab to slowly lift the pedal, then put moderate pressure on the pedal, then release the pliers, allowing the air/ fluid to escape out the open bleeder nipple.

Do this 8 or so times, that should be enough for most.
Doing this will also show you if you are getting pedal pressure in the cab or not, thus helping us diagnose the area at fault.

Is the mcyld getting too low on fluid when you bleed, thus dragging air into the system by accident whilst bleeding??
top it up after each 2nd stroke.

Sorry if we are doubling over things, and going back to basics mate.

Trains

Ray, I'll check the free play.. I am positive that when installing the new slave i adjusted the rod to the length of the busted slave. that being said though there could be more freeplay than normal. so I'll have another look at that.


Trains, thanks for the suggestions and I dont mind going over the basics again.. its a good way to ensure everything is covered and the issue pinpointed.. often hard to do when just replacing parts willie nillie like i have done..

I will spend some time on the weekend with the things you have suggested as the 40 will be a bit more regular of a daily driver in the next few weeks so its important that this issue gets sorted.

thanks again for your patience and taking the time to write out the basic steps to test it.

Andrew

well had enough of a dodgy clutch so looked at it this morn..

clamped off the flexible hose and the pedal was rock solid
then looked at the freeplay with the clutch fork and it was about 10-15mm of play.. almost wound the rod all the way out to take up the tension..

test drive proved successful but i have to remember i dont need my foot on the clutch any more

thanks to everyone's input sorting this out.. starting at the basics does the trick!