Sanity check on trouble changing gear..

[T16]

So, I was doing about 85mph for 1.5hrs approx.

Parked up in Glasgow, or tried to, and noticed that the car was EXTREMELY troublesome getting into ANY gear with the engine running. Heard big clunks from the box as I was struggling with putting it in gear.

The car was nice and toasty from its run.

Now, fast-forward to today and yesterday, when the car is cold it feels 100% normal again.

Any ideas what can cause this aside from the obvious? Low box oil meaning the box running too warm?

Im assuming its the clutch seal on its way out, and that when its warm, it makes the issue worse somehow, air past the seal or who knows what.

Sound familiar with a change in temperature of the box?

[COLVERT]

The clutch reservoir on the verge of being empty.

With the slave cylinder and pipes expanding with heat and taking slightly more fluid to fill them.----:eek:---Just not enough to go around.--:cool:

[T16]

Fair enough, Im happy enough I think its the slave/clutch.

I think if the box was low on oil, the problems would be evident regardless of the temperature of the box.

Well, thats my hunch anyway.

[marinabrian]

Fair enough, Im happy enough I think its the slave/clutch.

I think if the box was low on oil, the problems would be evident regardless of the temperature of the box.

Well, thats my hunch anyway.

The master cylinder make up valve is partially blocked, causing the CSC bearing to remain in contact with the diaphragm spring.

After being driven at speed for the period of time that it had, the heat generated would have caused the clutch fluid to boil, and the symptoms you describe.

When you replace the CSC, use the quick coupling from the old unit combined with a pipe joiner to fix the bleed nipple.

Remove the piston from the master cylinder, clean out the one way valve, and the hole in the piston, wipe out the bore of the cylinder, then refit the piston.

Using the bleeding device you have made from the old slave pipework, bleed the master cylinder until clear fluid is expelled from the pipe, then you can connect up to the new slave in the knowledge that it won't be contaminated with dirty old fluid ;)

Brian :D

[T16]

lol...

Im not doing any of that!

Master, slave, clutch all replaced at the same time....

:))))

[roverbarmy]

lol...

Im not doing any of that!

Master, slave, clutch all replaced at the same time....

:))))
I think that Brian :bowdown: is trying to save you a big bill. Cleaning as he describes can/will prolong the life of your slave/clutch.
Mike

[T16]

Ahh well cheers Brian.

But I'm not messing around, dont have the time, patience or energy to faff around with failing ZTs all my life.

If a part is on its way to breaking, its getting replaced.

Last thing I need is to be stuck in Albania/Ukraine/Norway with a failed clutch.

:) :) Appreciate the tips though.

[HarryM1BYT]

Ahh well cheers Brian.

But I'm not messing around, dont have the time, patience or energy to faff around with failing ZTs all my life.

If a part is on its way to breaking, its getting replaced.

Last thing I need is to be stuck in Albania/Ukraine/Norway with a failed clutch.

:) :) Appreciate the tips though.

Even fitting all new, is no guarantee of something will not to fail. Quite a few items generally fail in the first few hours of operation. Even the best maintenance only reduces the chance of an issue.

[marinabrian]

lol...

Im not doing any of that!

Master, slave, clutch all replaced at the same time....

:))))

There will be nothing wrong with the master cylinder Ross, and what I describe is actually quicker than replacement.

If it wasn't a proven method of doing the job, I wouldn't have suggested it........my previous "test car" had this done five years and almost 120,000 miles ago, and is still working well to this day, with the LUK Repset Pro.

What I will say is advice from someone who has used both methods for clutch replacement, remove the subframe completely, and don't do as you have in the past drop the subframe on one side.

This latter is a recipe for fatal slave cylinder errors, as well as actually being more difficult ;)

Brian :D

P.S. are you using the ZT to run drugs? :eek:

[T16]

Last time I did a clutch it was 60k miles and felt the same as new.

Ill stick with what I know...:)

Got a crane which will help doing it alone.

Master has too much wear in the eyelet that contacts the pedal stub, so might as well replace the lot for the best piece of mind I'll get driving an old ZT.

After that, rear upper arms. sigh

[andy willi]

replace the lot and buy genuine LUK master and slave .

andy

ps dont buy luk repset comes with valio pressure plate not good .

andy

[COLVERT]

Brian.

Quick question. There is a hole leading down from the reservoir to the part of the master cylinder that houses the piston. With no pressure on the clutch pedal fluid can flow freely back and forth through this hole thus allowing the clutch to fully engage. As the piston moves forward this through hole is closed off. Pressure builds up in the pipework and the clutch disengages.

Is this the hole you suggest is getting blocked and thus maintaining pressure in the slave cylinder ?-----------Phew, long question. ;)

[marinabrian]

replace the lot and buy genuine LUK master and slave .

andy

ps dont buy luk repset comes with valio pressure plate not good .

andy

Last one I bought had LUK, printed on the friction material, and stamped on the pressure plate, not Valeo :shrug:

In any case it was a considerable improvement over the rubbish National clutch it replaced, where the splined centre had parted company from the rest of the driven plate, strangely enough it had a Freelander LUK slave fitted too :getmecoat:

Brian :D

[marinabrian]

Brian.

Quick question. There is a hole leading down from the reservoir to the part of the master cylinder that houses the piston. With no pressure on the clutch pedal fluid can flow freely back and forth through this hole thus allowing the clutch to fully engage. As the piston moves forward this through hole is closed off. Pressure builds up in the pipework and the clutch disengages.

Is this the hole you suggest is getting blocked and thus maintaining pressure in the slave cylinder ?-----------Phew, long question. ;)

Hi John, the make up valve for the master reservoir is located on the end of the piston, and takes the form of a spring loaded poppet valve.

The returning fluid displaced from the slave when the diaphragm springs of the pressure plate compresses the slave, returns up the pipework to the master cylinder, moving the poppet valve from it's spring loaded seat, and travelling up the centre of the piston exiting through the hole pictured below, and back into the master cylinder reservoir through the hole in the bottom of the reservoir.

https://the75andztclub.co.uk/forum/attachment.php?attachmentid=72355&stc=1&d=1518631697

Blockages in this part of the circuit lead to varying bite point, the slave cylinder not releasing fully as you describe, and of course can be remedied easily by careful cleaning.

It is amazing that prior to purchasing a new master cylinder for upward of £150, that anyone with any mechanical savvy whatsoever wouldn't investigate why this was happening.

However Ross has said that the clevis on the end of the master cylinder piston pushrod is worn, and rightly points out that replacement is the best course of action for him in this case, and I totally agree ;)

Brian :D

[HarryM1BYT]

However Ross has said that the clevis on the end of the master cylinder piston pushrod is worn, and rightly points out that replacement is the best course of action for him in this case, and I totally agree ;)

Brian :D

The eye or clevis on my MC was also worn oval with use, so I guess it was the original. It seemed to cause a lot of lost motion as the pedal was pressed down and the pedal had to be pressed down hard to the floor when in brief traffic stops. Which was why I swapped it for the TAZU Mk II, which let me down out in the sticks and was replaced with the standard Rover part - both replacement MC's fixed the lost motion in the clevis nicely.

Even a small amount of wear there, is amplified by the leverage of the pedal.

[COLVERT]

Brian.

Thank you for going to all that trouble to give me an answer.---:bowdown:


Though why the fluid under pressure in the slave cylinder doesn't flow back through that valve when you push the pedal down beats me.

Something else must be happening that I can't grasp.---:duh:



PS.. I thought that the small valve at the end of the piston operated in the opposite way to the way you suggest in order to make sure that the part of the cylinder in front of the piston was always full of fluid.

It shut under pressure as the clutch pedal was pushed down. If it didn't close you could not generate the pressure required to disengage the clutch. ( Signed-------Puzzled in France. Lol. )