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Clutch won't disengage. Help me


Mike8199

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Seems like a master cylinder issue, but it's never a bad idea when changing clutch/master/slave to look at the rubber hoses for any deterioration or leaking, as that may lead to some air getting in the system. It seems like the master has air in it, so here is what you can do:

 

With the master out of the vehicle, put in in a vice. Grab an old clutch hard line out of a junker or whatever you have laying around, and bend it so that when fluid gets pushed out, it goes back into the reservoir. Fill the reservoir about halfway, and push it in and out like 100 times, then check and make sure that when you give it one whole push in, there is no air coming out. After that, install it into the vehicle, and bleed the system as you typically would. Check every single soft line/hard line connection and make sure they aren't wet with fluid and that it's all sealed, then after making sure you have a full reservoir, gravity bleed the system using the slave bleed valve for about 10-15 minutes. That is the best way to install/bleed a new master/slave combo. 

 

Like Mike said, make sure your master pushrod is attached to the clutch pedal with the fork and dolley, secured by the little pin so it doesn't fall out. 

 

If your do all that, and you're still getting no pressure, or the master won't stop spitting out air when you're bleeding it in the vice, your master was just a dud. 

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Replaced master cause of no pressure on pedal before. And i picked up a new soft line, slave, and master to replace the old everything. This is a new clutch (fresh build truck) harder clutch plate. Im thinkin its either the synthetic dot 3 i stuck in. (Maybe synthetic is to thin? Idk) or it seems as if the throw just isnt long enough from the slave to actuate the clutch. So im goin to try and change fluid. Then if/once that fails im going to custom make a custom rod for the slave cylinder (a longer one) to give it more throw. Il post an update and hopefully she gets fixed from either of these ideas.

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Seems like a master cylinder issue, but it's never a bad idea when changing clutch/master/slave to look at the rubber hoses for any deterioration or leaking, as that may lead to some air getting in the system. It seems like the master has air in it, so here is what you can do:

 

With the master out of the vehicle, put in in a vice. Grab an old clutch hard line out of a junker or whatever you have laying around, and bend it so that when fluid gets pushed out, it goes back into the reservoir. Fill the reservoir about halfway, and push it in and out like 100 times, then check and make sure that when you give it one whole push in, there is no air coming out. After that, install it into the vehicle, and bleed the system as you typically would. Check every single soft line/hard line connection and make sure they aren't wet with fluid and that it's all sealed, then after making sure you have a full reservoir, gravity bleed the system using the slave bleed valve for about 10-15 minutes. That is the best way to install/bleed a new master/slave combo.

 

Like Mike said, make sure your master pushrod is attached to the clutch pedal with the fork and dolley, secured by the little pin so it doesn't fall out.

 

If your do all that, and you're still getting no pressure, or the master won't stop spitting out air when you're bleeding it in the vice, your master was just a dud.

I have it all connected, the master is attached to the pedal via the rod and clip. I didnt bench bleed upon install cause of lack of required material. But wont bleeding in the vehicle act as the same thing? Just take longer? Im getting no air, just solid streams. And its brand new master, soft line, and slave line.

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So now there was a clutch change involved too??? and the old master went to the floor also???

 

Tells me there is a mismatching of clutch components.

 

Exactly what was changed? did you keep the old release bearing collar? Flywheel changed also??

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So now there was a clutch change involved too??? and the old master went to the floor also???

 

Tells me there is a mismatching of clutch components.

 

Exactly what was changed? did you keep the old release bearing collar? Flywheel changed also??

Ok besides the entire truck overhaul. I changed clutch, pressure plate, release bearing (kit). Master cylinder, slave cylinder, soft line. (Clutch kit is "LUK 06901) bought it off rock auto. For 83 nissan 720 z24. Oem flywheel. Old master just had floating stuff in it (was sitting with fluid in it fr 15 years) and wouldnt hold pressure)
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Sorry the flywheel was not changed?

 

Did the clutch 'kit' come with it's own release bearing collar? The collar is the thing the bearing is pressed onto and sits on the end of the clutch arm.

Yes it came with release bearing, not the clip.

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Sorry the flywheel was not changed?

 

Did the clutch 'kit' come with it's own release bearing collar? The collar is the thing the bearing is pressed onto and sits on the end of the clutch arm.

im starting to think its the pedal. I know im jumping around alot, but the pedal has an inch or so of play. Ima try and fix that and see what happens.
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I have it all connected, the master is attached to the pedal via the rod and clip. I didnt bench bleed upon install cause of lack of required material. But wont bleeding in the vehicle act as the same thing? Just take longer? Im getting no air, just solid streams. And its brand new master, soft line, and slave line.

Yeah, the bench method just makes it go faster, and you can insure that the master is fully functional. I know when I replaced my clutch components I had to screw the fork to the very end to insure that I could get it out of gear properly/shift without perfect rev matching. After a few hundred miles on the new master/slave, it seemed to "break in" a bit, and I was able to screw it in further. Maybe that has something to do with your issue. 

 

So now there was a clutch change involved too??? and the old master went to the floor also???

 

Tells me there is a mismatching of clutch components.

 

Exactly what was changed? did you keep the old release bearing collar? Flywheel changed also??

The old master going to the floor is kind of confusing... It may have just been a shot master, but it also leads to the thought that whatever is causing it was not changed. I'm still thinking that your master may not be holding pressure. Maybe just run down to the parts store and get a new one, and see if that solves it. 

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Slave should move about 1" if everything working.

 

YES slave moves... 

Assuming the slave/push rod/clutch arm are moving about 1" then the problem is inside with the clutch.

This could be the release bearing collar is the wrong size for the installed new clutch

Clutch disc is stuck to flywheel or pressure plate

Pressure plate is faulty, not releasing

 

 

 

NO the slave doesn't or barely moves...

Air still trapped in lines or slave

Master is no good

Master not bench bled and has trapped air.

Clutch pedal free play not adjusted to 2mm or 1/16"

 

 

 

1/ Pedal may be moving master but no fluid is moved. The internal seals might be missing from cheap Chinese manufacturing. Disconnect the slave hydraulic line and pump the pedal.... does fluid move??????????? Put thum over end..... got pressure?

 

2/ If pedal is moving fluid into the slave it has to move. Fluid can't just do nothing. If leaking he would have said so.

 

 

Possibly fluid is moving but master cannot deliver it in sufficient pressure to work against clutch resistance. Master is no good.

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I have had this issue occur twice, once each on two different vehicles, after installing a new clutch. I still don't understand the cause.

 

If all the hydraulics check out, try starting the truck while in first. Depress the clutch while trying, but already have it first. If you can get it started, go drive it around for 10 minutes, even if that's circles in a parking lot. Then try shifting with the clutch.

 

Twice I've had that free something up and those clutches never had another problem.

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Thanks all who gave ideas! I fixed the issue. Turned out was the master cylinder adjust linkage. Was too short. So i fabbed an attachment for it and adjusted it out, clutch almost has no free play now, and clutch disengages like half way down, not on or near the floor.

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Thanks all who gave ideas! I fixed the issue. Turned out was the master cylinder adjust linkage. Was too short. So i fabbed an attachment for it and adjusted it out, clutch almost has no free play now, and clutch disengages like half way down, not on or near the floor.

 

Always put the old and new side by side before installing, if the push rods are different lengths then put the old push rod on the new master.

The pedal should have been noticeably lower, I don't recall you mentioning this.

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  • 2 weeks later...

Always put the old and new side by side before installing, if the push rods are different lengths then put the old push rod on the new master.

The pedal should have been noticeably lower, I don't recall you mentioning this.

Actually it wasnt any smaller, just for some reason it wasnt long enough to engage the clutch. I think it being a harder pressure plate it needed a longer rod.

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slave moving at all at the bottom.?

 

I had to once put my finger on the master to block the hole then it got fluid to move.

Had to do something similar.... had no air coming out when I bled my clutch but still had no peddle... I did the the master cylinder by doing an extra line back into the master.... still nothing but with the pedal all the way to the floor I covered the end of the line released the peddle and the master started sucking the fluid.... removed finger repeated.. reconnected lines bled the slave and I got a nice peddle and good movement on the slave... bleeding the master first is a must..

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