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nissan
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Discussion Starter · #1 ·
hey guys, got one i cant solve for ya's


it all started yesterday morning when i went to leave for work, and had no clutch, had a look, no fluid.
so put some fluid in it, and drove it to work with the clutch system full of air and just rev matching cause it wasnt moving far enough.
by the third job i went to, the clutch was working alright, well enough for me to grab my trailer, and go pick up my project car from the shop, and tow it home, and get a new clutch master cylinder on the way home, as the reason for the lack of fluid was a leak out of the rear of the master.

so i fitted that last night, bled it, from both points, and gave it a quick test, felt perfect.

left for work this morning, and its fine, 10 minutes down the road, the bite point is coming up higher and higher up the travel, to the point where the clutch is slipping under average accel, and on hills.

got it to work, did what i had to do, and 4 hrs later drove home, seemed fine, but alas, again the bite point came up and the clutch started slipping again.

i spoke to the bloke in the store, who said put a couple of washers between the master and the booster, and this will fix it, but my issue with this is, it will fix it when its pressurised, but i doubt ill be able to get enough movement to use the clutch when its cold and not pressurised.

when i got home i pulled the booster out, set the pushrod lengths and reinstalled, and also set the pedal height.

when i re-installed the pushrod did not match the pedal height against the stop, so i wound it out some more to get the pedal up to the height its meant to be, with the correct free play etc

took it for a drive, did exactly the same thing, really, no difference. none.

re-bled the system but it seemed air free.

so ive got the ****s with it.

who knows whats going on here and can tell me what to do? is it the master cylinder faulty?

cheers, andy
 

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bleed it till empty and try again if theres no improvement it almost sounds like a bend push rod or piston damage in the slave cyclinder
 

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nissan
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If you have "overstroked " the master cylinder when bleeding, there may now be damage to the master cylinder wall or cup. Fluid is bypassing the piston and cup and building up.
This pushes the pedal further out and can cause this problem. I would be inclined to strip the master cylinder and check for scoring.
If the slave was rewted, it would most likely leak. Have you bled the master cylinder at the top bleeder?
 

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Ive had this exact problem before in my GQ , Replace the master cylinder again .
when i got my clutch booster rebuilt they supplied a new master cylinder that did this exact problem , they exchanged the master cylinder problem gone .
 

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i had this problem, it was a squashed brake line
cheers
 

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nissan
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Discussion Starter · #6 ·
thanks for the replies so far guys :)

bleed it till empty and try again if theres no improvement it almost sounds like a bend push rod or piston damage in the slave cyclinder
the only thing that has changed is the master cylinder, so im ruling out anything else in the system really.

If you have "overstroked " the master cylinder when bleeding, there may now be damage to the master cylinder wall or cup. Fluid is bypassing the piston and cup and building up.
This pushes the pedal further out and can cause this problem. I would be inclined to strip the master cylinder and check for scoring.
If the slave was rewted, it would most likely leak. Have you bled the master cylinder at the top bleeder?
how can you overstroke a clutch master? ;)
and yes, bled bottom and top twice now, second time was a waste of time, not even the slightest bit of air came out...

Ive had this exact problem before in my GQ , Replace the master cylinder again . when i got my clutch booster rebuilt they supplied a new master cylinder that did this exact problem , they exchanged the master cylinder problem gone .
this is what i thought but didnt wanna hear, i might put the old one back in and see what happens, it was only a small leak, im pretty ****in pissed off though, and im gonna be more pissed off when i have to swap it out again...

i had this problem, it was a squashed brake line
cheers
i dont get it?


cheers, andy
 

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along the diff the is a metal brake line, mine was squashes not letting through properly and i had very little brakes and it was presurising
 

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The nutty professor
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your pedal might need to be re adjusted , sounds like when the pedal is out the piston in the master cylinder is still blocking the hole from the reservoir so the fluid cant return to the reservoir, plus you still have air in there which is what is expanding
 

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Discussion Starter · #10 ·
well ive pulled it off now, going to try get a replacement tomorrow, im positive there was no air left in it, got nothing out of either bleed point the second time i bled it.
if there was air, surely the clutch would be spongy etc, which it isnt, and when it was full of air it didnt get better as it got hotter, drove it 35 mins to work and it didnt improve, whereas with this within 2 minutes you can feel the bite moving.

it moves a good 120mm up the pedal travel from cold to hot, and i dont see how heated air could apply enough force to push the pedal to the point of slipping the clutch...
 

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nissan
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Discussion Starter · #11 ·
ok, another new master, still no joy, doing exactly as described

bizarre considering all was good until i replaced the master :(

so, are we all thinking slave now?

anyone wanna tell me why its the slave?

im thinking it might be, considering the proximity of the exhaust to the slave, would be the most likely to be affected by the heat

i dunno though :(
 

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i had the same problem too mate. i had my booster rebuilt which seemed to fix it, it still changes pressure from time to time but nothing like it used too. used to give me the ****s big time, drove to melbourne with a furniture trailer one weekend went up and back no dramas, no clutch slip at all. got in truck the next morning and hardly had to look at the clutch pedal and it was disengaged and slipping like a mofo.

i have also replaced everything, ie master, slave and put a new clutch in when my motor was out and im convinced 99% of my problem was the booster. this was suggested to me from a 4wd service centre who had seen this problem before.

hope this helps you out;)

Jlowe
 

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I had the same problem after clutch booster rebuild and new master cylinder
My fix i made a gasket out of gasket paper and put between booster and master cylinder
Don't ask what thickness of gasket paper it was just a sheet i had lying around but it was reasonable thick
That was about 2 years ago and no problems since
Hope this helps
Only takes about 10 mins to do
 

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Discussion Starter · #14 ·
when you did that, didnt it change the position of the clutch bite when the motor was cold?
or was yours doing it all the time?
i just put my old one back in, and im now having no issues :)
 

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I didn't notice any difference
It only done after the booster rebuild & new master cylinder
I've know people who have had there old master cylinder re sleeved don't have this problem
 

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Discussion Starter · #16 ·
mmm, so was yours fine when cold and then went to **** when hot?

i just dont see how if you move the master away from the booster, which is moving it away from the pushrod, how do you have any clutch when the system isnt acting like a twat?

yeah im thinking ill either resleeve, or just put a seal kit in it and see what happens...
 

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Mine was pressurising the slave cylinder,holding the clutch fork out after only a short drive maybe 2 km's. Clutch pedal went to the floor and stayed there. If you undo the bleed nipple on the slave cylinder it would come good meaning fluid was not going back into the master cylinder.The hole was still covered . Moving it out solved my problem.
 

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Discussion Starter · #18 ·
yeah this does seem to be the consensus. think ill try adjust the pushrod and get it right, might be holding it the tiniest bit and resulting in blocking the return.


might leave it a few weeks, im sick of changing this stupid thing now
 

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Discussion Starter · #19 ·
yeah this does seem to be the consensus. think ill try adjust the pushrod and get it right, might be holding it the tiniest bit and resulting in blocking the return.


might leave it a few weeks, im sick of changing this stupid thing now
 

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Seal kit on the slave...bout tem bucks. Check all lines for crimps/kinks on rubber hose and metal line. Flush system as a grain of grit could be blocking the return (most probably near master cyl)....if none of this, go back to pushrod adjustment. mine was pushrod but these other problems will do the same thing.
 
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