R380 Clutch Low.

[Matt H]

Well it would seem it's clutch diagnosis time for the old Disco.

Driving the other day the clutch seemed very low with a hard, immediate bite. Perhaps only the last 2" had any effort with the peddle remaining close to the floor.
I checked the fluid level and it was low. Filled fluid and took a look underneath. There is some brake fluid visible on the bell housing. Managed to coax the poor old girl home and get her up on ramps.

I expect to find the clutch slave cylinder leaking, but not enough to cause the above problem by itself. I suspect that I may have fallen foul of the well documented broken clutch fork problem as well. On top of that I'm not entirely convinced the clutch master is either adjusted correctly or performing correctly? This is my first newfangled R380 gearbox so I guess we will see what's what as I disassemble and do some failure analysis.

I will try to snap a few pictures as I go and show what I find.

Now, seeing as this is a diesel conversion (not done by me and with ZERO documentation) I have no idea if standard 300tdi/R380 parts were used or if an improvised system was substituted? The Disco was a NAS spec V8 auto so who knows?? This is the biggest drawback of any undocumented modifications.

It does all "look" like a standard Rover clutch system but I will need to cross reference all the existing part # to ensure any replacements will match what I have on the vehicle. Or if any further modification/upgrades should be done. Let the games begin.

Bill, may need to hit you up for some parts  ;D

[Red90]

If the clutch fork fails, you will have no clutch action at all.  The slave fully extends and the pedal becomes rock solid.

Sounds more like air in the hydraulic from a leaky slave.  When the slave seals go, they tend to suck air in on the retraction.  Could be something worse, but that would match the symptoms.  Note the Disco "should" have a funky damper in the line before the slave.

[Trevor]

If the clutch fork fails, you will have no clutch action at all.  The slave fully extends and the pedal becomes rock solid.

Seconded. I had my fork fail on the Defender a few years ago and that is exactly what happened...no middle ground, the pedal went from working to full extention and solid.

[Matt H]

I did consider air in the system but the usual symptom of that is a spongy pedal feel as the air is compressed. Mine is hard. It could be leaking internally I suppose but then I would slowly get clutch re-engagement as the slave or master cylinder can no longer hold pressure. Mine will hold indefinitely. It's just really low.

Having said that, if fluid is getting out, chances are pretty good air is getting in. So air in the system is certainly on the cards.

Interesting info on the fork failure resulting in zero clutch release. Didn't realize this. That helps a lot.  Thanks.

Either way it looks like I'm going to need a new clutch slave cylinder. I'll know more when as I disassemble the system.

I'm assuming once the slave is off a guy can see into the bell housing far enough to identify a worn or failing clutch fork? Never been inside a R380 before.

[binch]

standing by Matt ;)

[Red90]

I did consider air in the system but the usual symptom of that is a spongy pedal feel as the air is compressed. Mine is hard.

Okay, your description is confusing me then....

With the slave off, it is hard to see much.  You will need a mirror and some fiddling.  The rod should be about a half an inch sticking out past the slave flange surface if everything is correct inside.  If it is further in, something is bad.  All of the clutch release parts have a limited life....the fork is just one of them.  If you do get into it, you want to replace everything from the master through to the pilot bearing.

[Matt H]

With the slave off, it is hard to see much.  You will need a mirror and some fiddling.  The rod should be about a half an inch sticking out past the slave flange surface if everything is correct inside.

Good to know. Thanks.

Hoping to find a couple of hours to investigate this weekend.

[Matt H]

Had two hours to check out the clutch issues on the old Disco last Sunday.
Poked about underneath and was pleased to discover that it all looks standard Land Rover. However, there were a couple of differences I had not seen before. No clutch adjustment at the MC and what looked like a dampener I hadn't encountered on a LR before?

Did a little digging in the parts book and found there is actually no adjustment of the clutch rod at the Master cylinder as you find in a R380 Defender. You just get a solid actuator rod. Also found a 300tdi/R380 Discovery has a clutch dampener that is not used on the V8/R380 Disco's or any Defender. Mine had both these features so it's looking like most of the donor parts used (at least as far as the clutch system) were from a similar model year Discovery. Good news.

Now I knew what I was dealing with It was time to find out what the problem/problems are?

I noticed before that the slave cylinder was weeping so I decided to start there. I removed it, checked the rod and clutch fork were ok, and had a dig around to see if I had a spare slave cylinder that would work. No such luck, the slave on a R380 is considerably different from the LT77 and Series III style. So, being equal parts cheap skate/make do and mend sort of bloke I stripped the slave cylinder down and inspected it for anything that would prevent it being returned to service. I found just light scoring on the bore with the seal in remarkably good shape. I cleaned the piston and seal. Honed out the scoring and rebuilt the slave cylinder. Tested it and found it to be satisfactory to reinstall.

Next I reverse bled the system and retested. Not much clutch effort was transferred to the slave cylinder. I then inspected the master cylinder and found the level to be fine. I now suspected a internal leak in the master cylinder. One test for this problem is to push the pedal down and see if the fluid level increases in the clutch master cylinder reservoir. It did. I removed it, stripped it and found damaged seals on the spool valve and badly scored cylinder bore.

So I have a new MC on it's way and hopefully will be back in business soon.