Clutch is only 1500km old. Was working fine till the other day. Started slipping without warning. Adjusted the master cylinder rod(Hydraulic clutch on L20b) and it worked fine for another day or two. Tried adjusting the master cylinder rod again today and it didn't fix the slipping. I noticed that the clutch grabs (engages and drives) after around 3 seconds after releasing the pedal. The pedal returns to the top slowly before it grabs.

Is it the master cylinder?

Don't really want to pull the gearbox off. Anyone had this problem before?

Maybe there is air in the system? Check for leaks and bleed the system maybe.
Or could be master or slave need overhaul.

Air, needs bleeding, bad slave - none of that can cause slipping.

What cam cause slipping:
* clutch needs replacing
or
* clutch has no play

To check the play, use your pinky finger to press the pedal. There should be at least 20mm before the pedal gets hard. If there is no play, adjust it at the clutch release lever under the car. The adjustment at the master cylinder is for something else.

If the clutch engages 3 sec after you release the pedal and the clutch is slipping I'd say master cyl needs o/haul,either sticking piston or blocked fluid return port
and I dare to disagree with the Master but you adjust the initial pedal free play at the master cyl push rod to give aprox 1mm free play between the pedal rod and the master cyl piston[aprox 20mm at the pedal] then adjust the slave cyl rod to give free play between the throw out bearing and the pressure plate fingers
Russ

Thanks Russ for the correction. Yes, the L20B clutch is adjusted differently than the 1200 clutch.

To check the play, use your pinky finger to press the pedal. There should be at least 20mm before the pedal gets hard. If there is no play, it can allow the clutch to slip while driving.

For both L20B and 1200 hydraulic clutch, the master cylinder pushrod length must be adjusted for a specified mm of play. Too little play can cause a sticky clutch. For the 1200 clutch master the pushrod is adjusted using shims, I believe it is 1mm at the master.

After you adjust the initial pedal free play at the master cyl push rod to give aprox 1mm free play between the pedal rod and the master cyl piston, then adjust the slave cyl rod to give free play between the throw out and the pressure plate fingers which results in aprox 20mm play at the pedal.

Thanks guys.

I should clarify that it is an r30 gearbox and a non adjustable pushrod on the slave cylinder from a bluebird (i think)

Does the push rod need to be replaced with a shorter one to give more play? Maybe the rod is too long therefore holding the clutch off the plate. There is only around 5mm play at the pedal.

Its strange to me that the ute drove fine for around 1500km before this happened (Although the clutch pedal feel was always soft)

Thanks again guys. This site has helped me greatly through this conversion. I just hope I can fix this without pulling the box off (again)

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Got a new MC. Cleaned the slave cylinder bleeder. Flushed the lines with new brake fluid. Bled the lines and Voila!

I bled the lines using the gravity method which I was sceptical about but it seems fine (and you can do it without asking ya missus to pump the pedal)

Happy Days

Congrats on fixing it.

Gravity bleeding is fine for that specific clutch slave because the bleeder is at the top of the slave -- along with the straightforward routing of the clutch line. May not work so well with the brake system.

So do you think the problem was caused by a bad master cylinder pushrod?

Inspecting the master cylinder after removal I found that the rod had free play(no resistance) for about 3/4 of an inch. Then it had resistance for the remainder of the stroke. May have been the seals. Not sure without dismantling it.

But thanks to everyone who replied for pointing me in the right direction.

Its engaging without slippage so I'll count that as a win

Now onto building some coilovers