P38A Clutch slave madness...

Been a little while since I have been on here, last time was a year ago and I was trying to find out if the front swivels should be set by eye or with the special tool... Still not got around to that..

Anyway.. It's been off the road for a year, so about a month ago I decided to bring it into the workshop and change the rear main seal (wasnt leaking but preventative) fit a new clutch and dual mass flywheel.

While the clutch was out, we did change the roll pins in the clutch fork and inspected the clutch fork fingers for wear and it looked fine.

Got it all back together, went to use the clutch and the slave dumped its fluid all over the workshop floor.

Brought a new slave from Island4x4 which took forever to arrive, fitted it and all seemed fine for about two miles through the industrial estate and about 20 clutch depressions and then pop, the clutch peddle stayed on the floor and I could engage all the gears without it, just not able to drive off..

So got it towed back to the workshop and lifted it up to find AGAIN the clutch slave had dumped its fluid all over the floor, the piston had almost exited the slave and was jammed in a cocked position..

Popped the piston back in, the seal was fine, and re-bled the system again.. tried the clutch... Lovely.. use the clutch a few times again while it was on a lift and again pop..

So I ordered a new clutch slave rod, a new cup for the clutch lever end, a new dust boot just to make sure that was all as it should be... fitted it, bled it, and again.. after a few depressions... pop

Looking at it, it looks like each time the clutch peddle is depressed the slave returns back not quite as far as the previous time, until eventually it over extends itself.

I am pretty sure we can exclude a clutch/clutch fork problem... But I am having a hard time figuring out what is happening here and wonder if anyone here has seen the same thing?

When it is working, the clutch feels as fine right up until the time it pops out, but something is stopping it from fully returning, so causing the clutch slave to slowly on each clutch depression to ratchet its way out until it pops out.

I have an independent Porsche garage (not as grand as it sounds) and the only time I have had a problem like this has been on 944/968 models, where an old flexi hose can break down internally and cause a "one way valve" effect, but usually this causes the clutch peddle to hit the floor and not return unless you get your toe under it and lift it up which causes them to flick back upto the top.

At the moment, unless there is something I am missing, I think the clutch flexi hose is suffering from this same kind of one way valve issue, or part of the master cylinder which evacuates fluid on the way back is not working... But another part of me thinks I could be missing something fundamental that you guys might have experienced before as a "ha ha you newbie, your missing the return spring" or something, but I can't spot what it is.

So, before I start playing car parts Russian Roulette, probably starting with the clutch flexi and then maybe the master, do any of you have any ideas?

Once I can get over this hurdle, I can find out if the front swivels can pass for another year, or if the MOT chap we use is going to decide "this is the year" that I need to choose if I should change them by eye or by using an alignment tool.. but thats for another topic!!

Oops - I just tried to edit the title, I should have added it is a 2.5 DSE... Sorry chaps

Does it have a anti stall valve on pipe that feeds the clutch slave .it lets the fluid return slower to the master ,a round thing half way along the pipe.

dubbleRR said:

Does it have a anti stall valve on pipe that feeds the clutch slave .it lets the fluid return slower to the master ,a round thing half way along the pipe.

Click to expand...

I will check in the morning, is that something that can cause this kind of problem and can it be ditched/bypassed?

Yes ,had one on a rover sd1 ,I replaced it with a bit pipe made the clutch much sharper and pulling away from junctions safer ...

Holy cow.. I have just been searching online for a clutch flexi for this beast.. between £55 and £75 plus VAT from many of the online places.. but BritishCarParts seem to have one listed at £6.17.. On the one hand, thats much cheaper, but on the other, am I missing something about why that one is cheaper, or why the genuine one is so expensive, it does just look like a traditional brake flexi though.. If the fittings are typical M10x1, I might see what Porsche brake flexi's I have that may fit to rule it out.

I suffered a very similar problem on my own P38. We found the clutch fork was bent or had damaged itself.
We only found out by placing it next to a new one.

Reminds me of my problem I had when I owned a P38 manual diesel years ago - got my mate to bung a clutch kit in it before I set off the next day for Greece towing our twin axle caravan. Collected the car from workshop, clutch felt ok ish but a too near the "bottom" for the bite point but anyway it was perfectly driveable. Only 10 mins to the ferry port, caught the teatime sailing for Cherbourg and left there at around 11 pm hoping to get well the far side of Paris before parking up for a rest for a few hours. All auto route so minimal clutch use but it was getting lower and lower with the bite point. Next morning after a seven hour rest set off again for the next leg to our friends who live at Annecy about an hour or so from the Mont Blanc tunnel. I had to stop after about 150 miles because the clutch was starting to drag. So I jacked up the suspension and ended up removing the slave push rod and replacing it with a 1/4 drive extension which was a little longer and bled it out thoroughly. It improved things a little but it was obviously not quite right. Anyway successfully made it to our friends house with a bit of a struggle early evening and parked up.
Here's the kicker - when I went to the car 24 hrs later for the next haul through the tunnel and to get to Ancona - guess what? It had fixed itself. Bite point restored exactly where it should be. I was dumdfounded but relieved and we successfully made it to our place in the Peloponnese.
About 6 months later I was doing some stuff underneath the car and thought it was high time I put the original push rod back which I promptly did and added my 1/4 drive extension back to my tools........
Whereupon it did the whole wretched thing again and sulked for a couple of days before mending itself.
Never did understand what that was all about - at no time was the hydraulics broken into so the mystery remains.
I can only think that pushing fluid back up the line towards the master must have caused it - done when the clutch was replaced and again when I retrieved my extension.

Last night I decided I wanted to have some hard information for diagnosis.
* How far the slave moves in relation to the clutch peddle being pushed from top to bottom.
* If the clutch slave was returning to the same position each time, if not how far was it ratcheting each time the peddle was used.

Had one of the chaps this morning run some tests, and the results are interesting.
It seems the clutch slave push rod moves 10mm for a complete stroke at the clutch peddle and that on each push, it fails to retract fully, usually coming short by between 5 and 2mm.

The other interesting thing is that at rest, the clutch slave piston seal is only 20mm away from the end of it's travel, which will cause it to leak, yet the clutch slave piston has about 50mm total available stroke, which I am also concerned about.

From this I was able to gather within reasonable doubt that the clutch flexi or clutch master is not allowing the slave to return 10mm worth of fluid back to the master, although it is able to fill the slave perfectly well.

So the next thing we will be trying is replacing the clutch flexi temporarily with a Porsche brake flexi that we have to hand, to see if that solves the ratcheting, which we presume is caused by a "one-way-valve-effect" for the clutch fluid.

If this solves it, then the problem is the clutch flexi was acting as a one way valve, if it does not, then the problem is in the master cylinder.

Which will leave me not comfortable with one remaining issue, the fact that even when the clutch slave is in its rest position, there is only 20mm of bore before the clutch piston seal will unseal, which is even worse when the clutch is engaged, as there will only be 10mm supporting the piston and before the seal is exposed and will unseal.

For this second issue, I have done some research and discovered that the original clutch push rod fitted to this P38 is 91.6mm long, but I also stumbled across an almost identical push rod, but 99.4mm long is used on the Disco2 TD5 and Defender TD5 (according to various web shops) which also seem to have the R380 transmission and again according to some web shops use the same slave cylinder.. I might be showing my ignorance here, but that if I use this push rod, at rest the piston seal will be 28mm into the slave housing, and at full extension will be 18mm into the slave housing, which should offer more support and keep the piston out of the danger zone a little bit more.

The Slave cylinder I currently have on there is a ANR2967
The push rod it currently has is 91.6mm long, the same as the original one that was on there, and has the part number FTC2170
The push rod I am thinking about using is 99.4mm long and has the part number FTC5199

Someone in the know might see these part numbers and instantly say I have the wrong slave cylinder on there, or they may say that at some point Land Rover had a recall on the push rod and slave and updated the part numbers, but the old ones are no longer available, which may mean I have a mismatch of a newer revision slave and an old revision push rod.. I have no idea.

I also have no idea if the original parts on this P38 were right, or if they were a cobbled together mess by a previous owner or garage. But I will keep this updated, along with any data I find, so in the future if someone else has the same issue, they might be able to find this thread helpful.

I will post what I find in the next round of tests.

Fergie46 said:

Reminds me of my problem I had when I owned a P38 manual diesel years ago - got my mate to bung a clutch kit in it before I set off the next day for Greece towing our twin axle caravan. Collected the car from workshop, clutch felt ok ish but a too near the "bottom" for the bite point but anyway it was perfectly driveable. Only 10 mins to the ferry port, caught the teatime sailing for Cherbourg and left there at around 11 pm hoping to get well the far side of Paris before parking up for a rest for a few hours. All auto route so minimal clutch use but it was getting lower and lower with the bite point. Next morning after a seven hour rest set off again for the next leg to our friends who live at Annecy about an hour or so from the Mont Blanc tunnel. I had to stop after about 150 miles because the clutch was starting to drag. So I jacked up the suspension and ended up removing the slave push rod and replacing it with a 1/4 drive extension which was a little longer and bled it out thoroughly. It improved things a little but it was obviously not quite right. Anyway successfully made it to our friends house with a bit of a struggle early evening and parked up.
Here's the kicker - when I went to the car 24 hrs later for the next haul through the tunnel and to get to Ancona - guess what? It had fixed itself. Bite point restored exactly where it should be. I was dumdfounded but relieved and we successfully made it to our place in the Peloponnese.
About 6 months later I was doing some stuff underneath the car and thought it was high time I put the original push rod back which I promptly did and added my 1/4 drive extension back to my tools........
Whereupon it did the whole wretched thing again and sulked for a couple of days before mending itself.
Never did understand what that was all about - at no time was the hydraulics broken into so the mystery remains.
I can only think that pushing fluid back up the line towards the master must have caused it - done when the clutch was replaced and again when I retrieved my extension.

Click to expand...

Fergie, that is truly weird.. But to be honest, what I have currently going on with this range rover is equally odd and similar in some ways...

Thinking about it logically, your problem could also be the clutch slave when bled for some reason not being able to return fluid back to the master and it taking a while (overnight) to stabilise.. But you would have thought that using the clutch a few times would see it back with a low bite point again until it had a chance to seep fluid back the next day again..

The Porsche cars I have been working on the for the last 28 years can be weird at times and have their own idiosyncrasies, but with the RangeRover P38 Diesel that is my only real experience of the Marque, takes weird to all new levels.. Needing a special tool to align ball joints for example?? When I found that out all I could say is "What??" and screw my face up.. But it really does seem that an alignment tool is the only way without buggering up seals by all accounts..

'Tis true, 'tis true - you have to realign the ball joints if you change them so that the driveline is correctly centred through the hub.

Don't know wether it helps but many years ago I had a Classic and had a problem with a new slave cylinder. The only way I could get it it operate properly was to fit the old piston on top of the new piston effectively it further back into the cylinderand allowing full travel of the push rod.

This is beginning to sound like there might have been an evolution or two slave cylinders fitted at the factory with different push rods, or the factory had a bit of a parts bin mentality, such as "we have run out of P38 slaves, lets use the XYZ ones from that line instead, we just need to use the matching push rods".. Who knows, not me for sure!

It could even be other manufacturers in the aftermarket have rationalised the stock to say "Rather than stock this one, as well as that one, why not just make this one and list it for both".. I see that with Porsche where Bosch made the original distributor caps for the Porsche 944, and Beru made the leads, some bright spark at Beru decided that the Volvo distributor cap they make would also fit the 944, so list it as fitting, as do German&Sweedish, EuroCarParts and others... Unfortunately it fits, but the distance between rotor arm and the contacts in the cap are wrong, so they run, but you loose about 20 bhp and hydrocarbons double... We spot the problem in a flash, but poor DIY mechanics with a faulty Bosch distributor cap use the Beru one and although it gets the car running, spend years afterwards wondering why the car was never the same again...

So times like this, when out of my area of knowledge, I do wonder what expert knowledge I am missing and can only get scientific on the case.

The P38 clutch flexi has two female fittings and is about a foot long, I was hoping it followed the same convention as many cars and the clutch and brake hydraulics are all M10x1 threads.. So I was hoping to fit a female to female random Porsche brake flexi to test my theory that the ratcheting slave issue is actually down to the flexi degrading internally.. But alas the P38 clutch flexi is a larger thread, something closer to an M12x1 or M12x1.25, certainly not M10x1, so that put paid to that experiment today, going to order one online that is apparently about £6.10 and hope it is right.. As mentioned before, the genuine one seems to be about £80!!! And one of the aftermarket suppliers is listing their one at £55.. So I will order the £6 one and see if it is right, I can not imagine the £80 is any more special than the £6 one, as it really is just a 12 inch long, female to female brake flexi and there is a lot less pressure in a clutch hydraulic system than a braking circuit.

Just to recap, at the moment I suspect the fault is the flexi breaking down internally making a one way valve valve in effect and that the only reason for wanting to change the push rod is there is little or no tolerance between the fully extended position of the slave piston and the point where it will leak or pop out, so the 8mm longer push rod should afford some additional margin for as the new clutch wears over time, or at least just to pander to my own paranoia!! lol

last time i came across a fault like that on a p38 the cross shaft snapped 2 days later

Sarbirus said:

This is beginning to sound like there might have been an evolution or two slave cylinders fitted at the factory with different push rods, or the factory had a bit of a parts bin mentality, such as "we have run out of P38 slaves, lets use the XYZ ones from that line instead, we just need to use the matching push rods".. Who knows, not me for sure!

It could even be other manufacturers in the aftermarket have rationalised the stock to say "Rather than stock this one, as well as that one, why not just make this one and list it for both".. I see that with Porsche where Bosch made the original distributor caps for the Porsche 944, and Beru made the leads, some bright spark at Beru decided that the Volvo distributor cap they make would also fit the 944, so list it as fitting, as do German&Sweedish, EuroCarParts and others... Unfortunately it fits, but the distance between rotor arm and the contacts in the cap are wrong, so they run, but you loose about 20 bhp and hydrocarbons double... We spot the problem in a flash, but poor DIY mechanics with a faulty Bosch distributor cap use the Beru one and although it gets the car running, spend years afterwards wondering why the car was never the same again...

So times like this, when out of my area of knowledge, I do wonder what expert knowledge I am missing and can only get scientific on the case.

The P38 clutch flexi has two female fittings and is about a foot long, I was hoping it followed the same convention as many cars and the clutch and brake hydraulics are all M10x1 threads.. So I was hoping to fit a female to female random Porsche brake flexi to test my theory that the ratcheting slave issue is actually down to the flexi degrading internally.. But alas the P38 clutch flexi is a larger thread, something closer to an M12x1 or M12x1.25, certainly not M10x1, so that put paid to that experiment today, going to order one online that is apparently about £6.10 and hope it is right.. As mentioned before, the genuine one seems to be about £80!!! And one of the aftermarket suppliers is listing their one at £55.. So I will order the £6 one and see if it is right, I can not imagine the £80 is any more special than the £6 one, as it really is just a 12 inch long, female to female brake flexi and there is a lot less pressure in a clutch hydraulic system than a braking circuit.

Just to recap, at the moment I suspect the fault is the flexi breaking down internally making a one way valve valve in effect and that the only reason for wanting to change the push rod is there is little or no tolerance between the fully extended position of the slave piston and the point where it will leak or pop out, so the 8mm longer push rod should afford some additional margin for as the new clutch wears over time, or at least just to pander to my own paranoia!! lol

Click to expand...

Or you could try my idea,just to prove/disapprove a point.I put my problem down to accumulated wear in the release linkage.

jamesmartin said:

last time i came across a fault like that on a p38 the cross shaft snapped 2 days later

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It is good to hear that some others have seen something like this before, that is what I was hoping for... Although I was not hoping to hear someone say that shortly afterwards something nasty happened!

What do you think the root cause was in that example? Was the area where it broke fatigued and showed signs it had twisted? Or was it something else?

Sarbirus said:

It is good to hear that some others have seen something like this before, that is what I was hoping for... Although I was not hoping to hear someone say that shortly afterwards something nasty happened!

What do you think the root cause was in that example? Was the area where it broke fatigued and showed signs it had twisted? Or was it something else?

Click to expand...

looked fine when i fitted box, it broke just inside the fork tube

tomcat59alan said:

Or you could try my idea,just to prove/disapprove a point.I put my problem down to accumulated wear in the release linkage.

Click to expand...

After reading your post we did try that.. Still ratcheting out, but I think that is the clutch flexi maybe.. But this time rather than the piston almost exiting, cocking, jamming the clutch in the depressed position and leaking all the fluid out, the outer piston almost exited, the piston cocked and jammed the clutch in the depressed position. Only difference was not having to re-bleed the system again as the inner most of the two pistons was still well within the slave. Hopefully the longer rod will achieve the same outcome but keep the piston way back and nothing to almost come out, cock and jam up.

I am open to any other ideas though, I even had a slight panic attack a little while ago as I thought that perhaps the clutch friction plate was in back to front (although they are usually pretty obvious and have flywheel stamped or printed on one side), allowing the entire geometry of the clutch arm to be around a few degrees more, but I am pretty sure the tech here that fitted it, did not screw up with such a school boy error.. Perhaps someone here with experience of the clutch on these might be able to comment if it would even be possible to get the disk around the wrong way... I know on nearly every car I ever changed the clutch on, the hub would stick out too far and foul the flywheel if put on back to front.??

Was it the correct pressure plate and release bearing? You did fit a release bearing? Sorry to ask but the release fork is traveling too far.