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PostPosted: Sat Jan 05, 2019 7:44 am 
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Hi All,
Got an issue with my 2013 dmax, being unable to shift into gear? Its fine if i shut the engine off, but otherwise its pretty difficult and sometimes requires a fair bit of force.
Ive just changed the fluid in the transmission and it hasnt really made a difference.
Just wondering if anyone else has had the same issue? And what they found? Was it the syncros or a replacement clutch? Something else?
Cheers

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PostPosted: Sat Jan 05, 2019 1:15 pm 
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Joined: Sat Oct 12, 2013 5:36 pm
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If the issue is, trying to get it into gear while running with the clutch pressed fully down, it is causing the synchros [which must be working ok] to block gear selection.
The cause? It is almost certainly the clutch not releasing sufficiently or it is has furry or disintegrating clutch plate.
First up, check and ensure the slave cylinder is working correctly and fully before considering replacing the clutch.

The slave/master system may have air in the system and even though the pedal is down, the clutch release bearing may not be moving to the proper/full extent. Bleed the system completely, ie, ensure no air before anything else.


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PostPosted: Sat Jan 05, 2019 1:45 pm 
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Thanks ill have a look at it later on this arvo. The slave cylinder is to on the transmission correct? Any tips on how to bleed it? Never had to do it before

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PostPosted: Mon Jan 07, 2019 10:02 pm 
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Joined: Sat Oct 19, 2013 10:23 pm
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Location: Darwin... sort of.
Marc.E.Sparky wrote:
Thanks ill have a look at it later on this arvo. The slave cylinder is to on the transmission correct? Any tips on how to bleed it? Never had to do it before


Very carefully...before you do anything jump under the car and have someone push the clutch pedal down and observe the slave (yes on the transmission) and see if the shaft is pushing the fork forward enough or at all, it doesn't have to go far but it should be obvious if it's only moving a few mm's, little or no movement would indicate possible air and you will have to bleed, be very careful as it's very easy to introduce air into the system and create a world of crap for yourself. If in any doubt of your abilities to deal with that should it happen better off taking it to someone and paying a few bucks to have them reverse pressure bleed it, it might save you an embarrassing tilt tray trip....

Bear in mind the factory clutches are rubbish on a DMax and if you have 40000k's or more or ever towed it could well be shot..

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PostPosted: Tue Jan 08, 2019 5:50 am 
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Unfortunately, if it is the same as mine, the clutch slave cylinder active end has it's bolted face facing the front and is secured to the bell housing. Therefore, you can't see if the piston or push rod is moving.
That all makes it hard to find the problem.

To see if the clutch is releasing, I would raise the rear wheels off the groung, on axle stands, have it in 4th gear with engine STOPPED. Then try and turn the tailshaft. It should not turn. THEN, get someone, as Danny suggested, to push the clutch pedal to the floor and hold there. Now try and turn the tailshaft, there will be drag but it will turn if clutch released. Continue holding the pedal down and wait a minute or two.

Now try and turn again. If it now is hard to turn or can't turn, then the clutch is closing by itself.

This is to check IF the system is leaking pressure past it's internal rubber seals and allowing the clutch to close again. If it does leak,it is unseen, but being able to turn the tailshaft and then not being able to, indicates a hydraulic leakdown and intenral seals of the master cylinder and or the slave culinder may the at fault.

A lot of testing but does indicate a few situations for diagnistic purposes, which can't be done via the internet.


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PostPosted: Tue Jan 08, 2019 8:35 pm 
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Joined: Sun Nov 27, 2016 10:56 pm
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Hi guys. Just an update:
Both master and slave cylinders had no visable leaks. Peeled back the rubber boot on the slave and still nothing. Clutch fluid level was ok. But then the problem worsened and i couldnt even shift out of gear! I also noticed that the pickup point for the clutch was getting lower and lower to the floor..
I had someone work the clutch pedal while i watched the stroke of the slave cylinder. It moved rought 5mm which was nowhere near enough.
Bled the lines and found the fluid that came out was quite dark. And yeah, there was a bit of air in the system. I bled it while topping it up with fresh fluid until i had no more dark fluid.
Now its perfect, the slave stroke is now roughly 25 to 30mm and its never been better, shifts better than than it ever has.
On its 60k service back in Aug/18 the fluid was "replaced" but i suspect not, or they use a different type of fluid to what was in the system already and they didnt react well..

Still, there was air im the line and it got in there somehow over time. I'll be keeping an eye on it
Ive got a replacement slave cylinder just in case

Man im relieved..
Cheers for the suggestions.

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PostPosted: Wed Jan 09, 2019 8:01 am 
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Marc
If the master cylinder is grubby inside and the larger of the two holes,ie, the rearmost one in bottom or reservoir, is partially blocked it can cause aeration of the fluid. When the master cylinder piston is released quickly, fluid from the reservoir MUST flow freely into the master cylinder to make up for the lack of back flow from the slave. As the slave returns to normal , any excess fluid in the system then re enters the reservoir through the primary port and everything returns to nil pressure in the system.
If the compensation port, big one is restricted, as the piston is forced rearwards by it’s spring it is faster than fluid returns from the slave. Therefore, if the big hole restricts fluid “makeup flow” then the master cylinder sucks air into itself through the momentary collapsing of the rear piston seal, ie, one way flow. Then you have actuation problems of not enough movement cause by the air compressing. Bleeding it fixes it but doesn’t rectify the cause.


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PostPosted: Wed Jan 09, 2019 6:28 pm 
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Mydmax,
Thanks for the info mate. I think regardless ill be re checking the fuid in a few weeks/month just to see if has changed colour. If it has, then ill be purchasing a new master cylinder. But for the meantime my bandaid seems to be holding.

Cheers again. Hopefully this info helps someone else

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PostPosted: Wed Jan 09, 2019 7:52 pm 
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Marc
The fluid won't change colour much unless a long time has expired and moisture has also contaminated the fluid.
If fluid is dirty at any time I would not replace the master cylinder or slave unless you can prove the seal cups on the pistons are either leaking externally (slave cylinder) or the master cylinder leak down under continued pedal depression and the clutch begin to engage, ie, the trouble you had originally.

By sucking out all fluid from the reservoir and leaving the master cylinder itself full of fluid (don't touch pedal) you should be able to see if the larger port, ie the rear most one is dirty and or restricted. That is worth a check for reliable continued operation.

If the small forward port is blocked then residual pressure will be held in the system and slave won't return to fully rest position. If that port is dirty you can probe it with a small drill, about 0.5mm dia they are. Any crud pushed into the master cyl then has to be flushed right through.


I often suck all fluid out, pour in methylated spirit and turbulate the reservoir with a small stiff brush. You can carefully blow out the reservoir or wipe it out, and then refill with fluid and thoroughly flush/bleed.

Many,many mechanics places only change thereservoir fluid but not the vital fluid in the hydraulic section of it all. Corrosion of both cylinders can then happen prematurely.

I had a Toyota landcruiser for 25 years and never had to repair either the brake or clutch, master or slave systems other than proper servicing.


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