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Odd clutch moment


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Just took the horse trailer round the fields to collect some large tree branches that had fallen the wrong way when cutting. The field is quite steep and i had to reverse the trailer a short way up it. This inevitably meant riding the clutch a little with revs - nothing major that I havent done before. I should have stuck it in low range and ridden the clutch less but was being lazy.

As I came off of the clutch fully, the pedal felt funny and it didnt return up fully. I just hooked my toe under and pulled it up. Pumped it once and after that it behaved fine for the rest of the evening (several more trailer loads dragged round to the yard). 

Any thoughts?

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I'd also check the clutch fluid and look for any signs of leaks. Had the same happen to my Esprit a few weeks ago, before she left me stranded in downtown Brussels with no drive, because the master had failed and stuck in the depressed position. The Esprit uses the same Girling master as the Defender, but with a smaller bore.

Filip

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How do you tell the difference between a failed master and failed slave cylinder. I know many say to replace both at the same time, but I am curious at how you distinguish the difference? A leak is (well can be) obvious, but if one fails internally, what are the different signs between the two? I think I must have had three slaves to one master cylinder - in fact I am not even sure I have ever changed the master in the 12 years it has been my daily driver , I don't know if mum ever had it done in the 18 or so years she used it daily!

I will give it a thorough check over.

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I never saw the point in replacing master and slave at the same time. The Range Rover seems to be eating slaves (the exhaust leak probably isn't helping) without effecting the master, the Esprit recently needed a new master, slave is fine. If the slave fails, you will get a leak, and shoudl be easy to spot. A failed master can leak, but often harder to spot because it's well tucked away. A master can also fail without external leaks, if it allows pressure to flow back to the reservoir instead of into the pipe to the slave.

Filip

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Thanks Filip - its that last sentence that I worry about as it is hardest to diagnose. Leaks should be obvious if I look hard enough. It was raining earlier so I havent checked it but did 40 miles this morning and its currently behaving.

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On 4/24/2019 at 1:21 PM, Escape said:

I never saw the point in replacing master and slave at the same time. The Range Rover seems to be eating slaves (the exhaust leak probably isn't helping) without effecting the master, the Esprit recently needed a new master, slave is fine. If the slave fails, you will get a leak, and shoudl be easy to spot. A failed master can leak, but often harder to spot because it's well tucked away. A master can also fail without external leaks, if it allows pressure to flow back to the reservoir instead of into the pipe to the slave.

Filip

I always felt the advice to replace both even when only one is faulty was just a sales technique, or maybe came about from mechanics who worked on cars where it was difficult to diagnose which had failed.  A slave cylinder is very simple, and if it has failed, it'll be leaking.  The master may fail so that the valve to the reservoir allows backflow and doesn't leak externally, but if the pedal moves, operates the master push rod and there is no external leak, then it has to be a master failure, so diagnosis isn't usually that difficult.  This, of course, assumes the system is bled and the release fork, release bearing/collar and pressure plate are good.

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I think there is some logic to swapping out both, but it will depend on your vehicle history.

If you replace the slave, the mere act of bleeding the system can push the master beyond its normal operating stroke, perhaps picking up a bit of rubbish, and nicking the seal. New master time.

Also, if one is leaking, there is opportunity for moisture to get in and corrode bits, making the above more likely.

Also, clean brake fluid is very good at cleaning stuff, removing any sludge that may be in there helping a seal, seal. By washing it away it can cause an earlier failure than would otherwise have been.

So if you know your vehicle history, then go for it, just replace the slave. On my Audi, the slave went recently, at only four years old, I had to replace the master shortly after (the original 28 year and 200,000 miles old), so I know that is still good, and it is not showing any leaks. So, I shall just replace the slave. I was getting some other odd symptoms, so I am also replacing the pipe/hose from master to slave (£100 from Audi) to make sure I don't have any further problems.

If you open the cap on your master and it is full of black sludgy stuff some might call brake fluid, then it may well just be a good idea to do the lot.

 

 

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It's certainly been my experience that if the slave fails the master is not far behind. 

So I change them both together. It's a simple job, a relatively inexpensive part and you've already got the clutch circuit open. Why wouldn't you ? Saves wondering if the master is going to fail in a week or two and buying more fluid and bleeding again !

Mo

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The thing that always puts me off of bothering with the master is the spanner access at the back of the master. It just takes ages to faff with those two bolts that hold it to the pedal pivot!

I cant find an obvious fault - no leaks at all. Could this just be a one off as also experienced by Ralph?

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I had the same thing - happened once then nothing for ages and then started doing it more often. It was the  master on the way out - given they are both inexpensive I'd replace both if they're of a similar age (I did).

I don't remember it being that much of a pain on my 300Tdi. I removed the whole pedal box complete though. On mine if I remember correctly it's bolts from inside the footwell that go into welded nuts, either 4 or 6 of them. Once that was done a bit of jiggling around and twisting through 90 degrees saw the whole assembly come out in-tact. While it was out I took the opportunity to repaint the bulkhead under the box and painted the housing as well.

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4 hours ago, reb78 said:

The thing that always puts me off of bothering with the master is the spanner access at the back of the master. It just takes ages to faff with those two bolts that hold it to the pedal pivot!

Plenty of lube and wire brush in a drill to clean the threads before reassembly, then the nuts will just spin on and off easily.

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  • 4 weeks later...

Just to raise this again. My biting point is sinking lower and lower - i now have about a third of the pedal as free travel before I feel any resistance. No leaks so I guess it’s definitely pointing to the master. 

I will try and get both today and change at the weekend. 

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