GQ 5L Conversion slave cylinder issues

[A.R.T Racing]

Hi guys,

Thought i should start my own thread and try and sort this out.

Its a GQ Ute with a 5 litre holden that has previously been in good running order. I put in a NPC clutch plate and used the old pressure plate and NPC confirmed all good to still use. Only put in new clutch plate as old one was a little worn and it was all pulled apart anyway.

Now we had alot of trouble bleeding the clutch system then finally got it all sorted out. But in between the adjustment rod at the pedal/master cylinder was adjusted twice. The car is driving now and we took it for a run to Double Island Saturday and had trouble after an hour on Bruce Highway with clutch losing freeplay. I adjusted the rod at the pedal then got freeplay. Move the car forward and use clutch pedal a couple of times and then no clutch. Adjust rod again to get a pedal and drive, after awhile there is no freeplay and i do it all again, and again...

Took the car for a drive this arvo all good after about 40min of driving around 60 to 70 and a bit of 100 stuff no freeplay. Check slave cylinder and its locked up solid. Couldn't even move it levering off the exhaust. Adjust pedal again and freeplay, then engage clutch couple of times and no clutch. Adjust pedal again to get clutch.

It seems that there is a problem with the master cylinder would this be correct? Why when there is freeplay the slave cylinder can push in but when no freeplay its like the whole system is rock hard with the fluid?

Anyone got any ideas??

[boost is good]

Sounds like when you adjust the master cylinder up to get a pedal you adjust it past the transfer port which allows the fluid to return to the reservoir so it feels rock hard when you try to push the clutch fork back with a lever (effectively the same as having your foot still half on the clutch). Also as everything heats up the fluid can expand and not get back into the reservoir so it slowly pushes on the fork until the clutch starts to slip. You need to adjust the master cylinder so that rod has a few mm freeplay before it starts to move the master cylinder piston ...
Sometimes its easier to reverse bleed clutches (push fluid from the slave cylinder backwards up through the master cylinder.. have to do it all the time on european stuff)
Hope this helps

[A.R.T Racing]

Well the car had a day and a half at Direct Clutch Services and they are telling me to get custom made extractors made to keep the head away from the slave cylinder. Has anyone else with a 5L in a GQ running the 4.2 Gearbox had to do this?

I honestly cant see that its a heat issue considering the truck ran for about 12 months a couple of years ago with the lines in the same place and it was fine then...

Now the car is at On Off Road Mechanical my money is on Mike to find the problem!

[UR-50-LO]

Maybe with a new, meatier clutch your not getting the rod travel needed to disengage clutch?
I had to run a GU 1-1/6 master in mine for this reason, but you could also get your slave sleeved...

[niss50]

Did you know there is two size thus bearings for that setup witch will make a diffance

[nisson35]

i have a 5 litre in a patrol and i have to keep shortening the slave cylinder shaft cause after 200 k's it starts to slip, even worse offroad with constant clutch use

[simcoe]

iv got a 5.0l in my gu running the original tb45 slave and master cylinder using a HD chev clutch which your not supposed to use because of the input length or something, but we machined it down and its all sweet.

i only need the bottom 1/3 of my pedal to engage the clutch and the only real main prob was the exhaust collectors ran directly under the slave which made the clutch sticky when at running temp, so i wrapped the hell out of the exhaust where ever i could around the area and now its fine.

oh and for some silly reason i get a sqeal when the clutch is pressed about 1/3 in from being dis engaged. only happens for about 20mm of the pedal.

[A.R.T Racing]

Thanks for the replies guys.

Mike from On Offroad Mechanical has sorted it. He put on another vacuum pump that i already had laying around and what a smooth action the pedal is now.

Just drove it for 1/2 hr and all working perfect. Will take it for a good long run this weekend but it definately feels much better.