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Clutch Hydraulics


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The clutch on my car has been playing silly buggers recently and I'm 99% sure it's the hydraulics. Symptoms are that the point in the pedal travel at which the system starts to actually engage the clutch levers seems to move about a bit. Apologies if this all gets a bit subjective, but it's hard to describe!

The normal position, at least what it's always been before, is that the pedal has the standard amount of free play in it as per the setup procedure in the manual, and then you immediately start to engage the clutch release arm, so the clutch is disengaged by approx. half way down the pedal travel.

What seems to happen is that somehow a load more free play is introduced into the system and the release arm etc, only seems to engage at about half way down the travel, meaning you only just get the clutch disengaged by the bottom, there's about 1/2" to spare before hitting the floor. What is even weirder, and this is also what makes me thing it's a hydraulic problem rather than a mechanical one, is that this problem will come and go randomly while driving. Quite often it shows itself soon after setting off first thing, but during the day it could correct itself and be back to normal.

This extra free travel has no resistance to it, so I am presuming there must be some intermittent fault with one of the cylinders whereby the seals are ineffective for a portion of their stroke within the cylinder itself. Either that or perhaps air in the system? But I would have thought that would be fairly consistent as a fault.

Both cylinders are not that old, the slave is 15 months and the master perhaps half that. Both were TRW branded ones too, not cheapo stuff. The clutch hydraulics have given me problems before, with the slave cylinder failing twice, is it one of those cases where you just can't get quality parts any more?

Any ideas anyone?

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Well here's hoping it's not that! Would rather not have it all apart if I can avoid it, though it probably wouldn't hurt to do the clutch as I've not done it in the 75k miles I've had the car.

I think I should be able to isolate the master cylinder by clamping the flexi hose and seeing if the problem remains. If so then the master is at fault, if it makes the pedal solid then the problem lies either within the slave cylinder or in the bellhousing.

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  • 1 month later...

This problem is still extant, at the moment it's having a funny day - clutch actuation still works fine but it has moved to the very bottom of the travel. Literally the pedal against the floor just disengages the clutch, so not much room for further movement! Still plenty of fluid in the reservoir but it's very black, which I presume is the remnants of a seal breaking up somewhere?

I finally got around to clamping the flexi hose today too - at which point the pedal went nice and solid so I am sure the problem is not in the master cylider, or the hose above the point where I clamed it (about mid-way). So I have ordered a new slave and hose and will swap them out shortly. Will put some clean fresh fluid in too of course. Hopefully this will solve it, it's certainly worth a try before going to all the trouble of changing the whole clutch assembly.

The last two replacement slave cylinders have both been TRW branded ones, so not cheap aftermarket s**t, but this will be the fourth unit on the car in my ownership (coming up on 80,000 miles). This seems a rather high failure rate to me, so I am going to try a Delphi one instead this time and see if that fares any better.

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What engine/transmission?

The one experience I had of this sort of thing was a couple of decades back on a 200TDi when the fulcrum-ball was slowly punching its way through the horrid low-budget pressed steel clutch release-fork.

When it finally let-go I ended up doing a 100-mile drive in Friday-evening traffic from Caterham round M25 and back along M4 to Wiltshire, doing clutchless gearchanges.

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have you checked the master cylinder pushrod locknuts are still tight, not wandering along the thread so making pedal operation sloopy

Master is fine I think Ralph, as when I clamped the hose the pedal was solid. So I'm pretty sure that the problem is downstream of he flexi hose.

What engine/transmission?

The one experience I had of this sort of thing was a couple of decades back on a 200TDi when the fulcrum-ball was slowly punching its way through the horrid low-budget pressed steel clutch release-fork.

When it finally let-go I ended up doing a 100-mile drive in Friday-evening traffic from Caterham round M25 and back along M4 to Wiltshire, doing clutchless gearchanges.

It's a standard 200Tdi with LT77 so yes, it has the pressed steel release arm. Hopefully it's not that, but if the new slave and flexi done solve it then the engine/gearbox will be getting split anyhow so will swap it out for a reinforced one.

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What engine/transmission? The one experience I had of this sort of thing was a couple of decades back on a 200TDi when the fulcrum-ball was slowly punching its way through the horrid low-budget pressed steel clutch release-fork. When it finally let-go I ended up doing a 100-mile drive in Friday-evening traffic from Caterham round M25 and back along M4 to Wiltshire, doing clutchless gearchanges.

I'll vouch for that not being a pleasant journey even with a working clutch, it's fairly often stop start traffic on the M25 on that section, especially if it was in the recent years of seemingly constant road works.

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