Offroad-Express

Hi all.
Here is my story. Just finished my LWB TD42 patrol that has been off the road since 07. I have turbo'ed etc. Have not touched fuel yet so turbo maxed out at 8 psi and egt temps very low, so lots of room for more power. Took her for a test drive on Friday. I installed a brand new 4terrain clutch when I had the engine out anticipating the power increase. Standard clutch I removed was working perfectly and was less than half worn. Flywheel was perfect condition, so I didn't bother getting it machined before installing new clutch. On the test drive (have only travelled 40 km). The clutch started to slip towards the end of the test drive when I really put the boot in (remember, I have not touched fuel yet, so it is not making huge power yet). The pushrod between the clutch booster and hyd cylinder was adjusted for clutch engagement in the last 1/4 of pedal travel, so I don't think it is holding the pressure plate just slightly off, reducing clamping force. I guess what I am asking is anyone had a similar problem? do I need to take fly wheel back out and get it surfaced? Have I got a dud clutch from 4terrain? Will re-surfacing fix the problem or have I ruined my new clutch already? Hoping there is an easy fix but expecting to be told that the fly wheel will need surfacing.

Cheers

Jase.

some times aftermarket main clutch cylinder has been machined to close to the bolt patten end and has a longer push lenght so at rest its engauging the clutch a bit

That is worth investigating. I failed to mention that I fitted a brand new after market clutch master and slave. Will have a look at that. Thanks coxsy.

yes it happen to mine by a garage I don't use now, killed my Xmas one year

any grease or oil possible? got warm after drive and the lubricant starting spreading over the surfaces?

even though the fly wheel may appear fine, no grooves or cupping of the friction area, if it is glazed (polished) upon installing a new clutch plate it will only help to polish the clutch plate smooth too.

No oil leaks. I lightly greased the release bearing carrier, but made sure there was no excess. Will certainly have a very close look for oil or grease contamination if I end up having to take the clutch back out. Glazing may be a possible cause and will inspect when/if the clutch is disassembled. I will investigate the hyd system first then consider the other possibilities. Thanks for the feed back.

I had the same problem, with the same brand of clutch. The slave cylinder was getting hot from the exhaust pipe and expanding the clutch fluid, just enough to make the clutch slip.
It only happened when in traffic and off road. Still had the factory slave cylinder as well. I just shortened the slave cylinder pin by about 3.0mm and it hasn't happened since.

Another very easy thing to check. Thanks for that. I have just put a three inch exhaust on it so it will be sitting slightly closer to slave. Did you still have the factory heat shield fitted over the slave when this happened? Mine is still fitted. Cheers Jase.

That disappeared years ago. I did put some high temp brake fluid in it last week, to make sure this problem doesn't happen again.

So to add to this...
I removed the master cylinder and compared it side by side to the old one I had replaced it with. The piston on the new one sits about 10 mm closer to the mounting flange on the new one. I mounted it up again to check the assembly on the clutch booster and there is no way that this master cylinder can return the piston all the way home. This was a brand new one from B n T. Looks to be a cheap Chinese copy. So I re built the removed master with new seals and have installed that. Finally got around to test driving it today and I could not detect any clutch slip. So figures crossed it was the new master cylinder at fault.
Will be adjusting the fuel now to give it quite a bit more power. Will be interesting to see if the clutch continues to behave itself.
As an added precaution I heat wrapped my exhaust pipe with ceramic wrap where it passes the slave cylinder and I still have the factory slave cylinder heat shield installed.

Thanks for your replies and sharing of knowledge. Once again this forum proves to be a valuable resource.

Same problem came back for me over the holidays as well. I pulled the master cylinder off and they were exactly the same size, but there were some very bad wear marks on the side of the piston and the bore. Looks as though the piston was jamming and blocking off the valve. Cleaned the old one and put it back in and problem gone again.
This will be the last time I buy a chinese master cylinder.
As it turns out, the heat should not affect the slave cylinder at all. If the fluid heats up and expands, it should go back into the master cylinder reservoir. You should always be able to push the slave cylinder piston in. If your clutch slips again this should be the first thing you cheek. If you can't push it in then you still have a problem with the master cylinder or the free play in the clutch pedal.