Section : Clutch

Tapping when clutch depressed 

Posted By : David Sibert, 25-Jun-2007, 09:10pm

When I even touch the clutch pedal gently, even before there is any hope of it disengaging, a &8220;hollow tapping&194;&8221; sound appears. It increases in volume as I push the pedal further, and it increases in frequency as the engine revs rise.

I thought it could be end float on the crank pushing the cam timing chain sprocket forward, and causing something (like the tensioner) to clip the timing chain cover. But:

I can&8217;t see any end float
I changed the cam chain, the tensioner and even the crank sprocket just to be on the safe side &8211; didn&194;&8217;t make any difference
there weren&8217;t any marks on the inside of the cam chain cover when I changed everything, and
this tapping starts as soon as I even rest my foot on the clutch, so;
If it was end float allowing the crank to move forward, it would have to be very sensitive (so I would have thought noticeable), and
(ii) The engine has only done 4,000 miles since a very expensive rebuild by someone I trust to have put thrust washers in properly.

So:

* has anyone ever experienced anything similar?
* Does anyone want to hazard a guess as to the cause even if they haven&8217;t experienced the problem themselves?
* Was I was let down by the engine rebuild?
* Could an invisible gnat&8217;s thingy of excess endfloat be enough to cause a tapping at the front of the engine?
* Could something in the clutch or the thrust bearing be at fault?

I would appreciate any thoughts. It was bad enough changing the cam chain bits and then finding that the damn thing was still tapping. If I take the gearbox off and change the clutch without fixing the problem I will be very unhappy bunny.

Many thanks,
Dave

• Tapping when clutch depressed 

  Posted By : Mark Hammond, 25-Jun-2007, 09:30pm

  Just a thought, could it be the dynamo or water pump bearings? Just remove the fanbelt then try it. Had a similar fault on my 1200 last week and it turned out to be water pump bearing failure and I could have sworn it was at the gearbox end. Noise does travel on an engine!
  
  Mark

  • Tapping when clutch depressed 

    Posted By : Ed Weller, 25-Jun-2007, 09:47pm

    I recently had the clutch fork go on my Vitesse - the fulcrum pin punched a hole right through it!! I'm not sure if Herald has the same set up, but if so wear and tear on the fork could be trying to skew the release bearing/carrier causing your noise. Just a shot in the dark!!!

  • Tapping when clutch depressed 

    Posted By : David Sibert, 25-Jun-2007, 11:10pm

    Mark,
    
    Thanks for that, I like things that are easy to check. I'll whip the fan belt off tomorrow evening and let you know the result.
    
    Regards,
    Dave

    • Tapping when clutch depressed 

      Posted By : David Sibert, 25-Jun-2007, 11:23pm

      Ed,
      
      Thanks for your idea, but one thing I failed to mention (in case it confused the issue) is that I have had a peculiar 'annular&8217; slave cylinder fitted.
      It sits inside the bell housing, bolted to the front of the gearbox, wrapped around the input shaft. It has braided hose coming from the master cylinder directly to it.
      
      The master cylinder forces a doughnut shaped piston in the slave cylinder to act directly on the back of the clutch release bearing.
      
      So unfortunately your suggestion won't win the prize, but many thanks for taking the time to write.
      
      Best wishes,
      Dave
      

      • Tapping when clutch depressed 

        Posted By : Peter & Mick Lewis, 26-Jun-2007, 10:35am

        The annular slave set up is the best way to operate any clutch where did you get the kit from,, any clues please
        and the noise is probably just diaprhagm finger runout often reproduced due to the bearing skidding in the fingers,often disappears with use peter
        

        • Tapping when clutch depressed 

          Posted By : David Sibert, 26-Jun-2007, 01:20pm

          Dear Peter,
          
          The annular slave cylinder came from Racetorations in Gainsborough (http://www.racetorations.co.uk). Talk to Darryl, tell him I sent you.
          
          I can't guarantee that this thing will fit onto your gearbox, another thing I forgot to mention is that I have a TR6 gearbox fitted to my car. Anyway, Darryl is one of the most helpful people I have met on the Triumph scene (although not the cheapest to say the least, he is worth the money) and I'm sure if it is possible, he will know.
          
          As for the idea of my tapping being "diaphragm finger runout", I've never heard of "diaphragm finger runout", but it is the best idea I've heard so far - especially the bit about it disappearing with use!!
          
          Any idea how much use? i.e. could it still be "diaphragm finger runout" if it is still going on after 100 miles? 1000 miles? Or should it have stopped by then? (I assume this would depend on whether I am talking about 100 miles on the motorway, or a 100 miles round central London but any further information would help).
          
          Thanks for taking the time to write
          Dave
          

          • Tapping when clutch depressed 

            Posted By : Chris Taylor, 26-Jun-2007, 06:37pm

            You MUST check out any possibility of missing thrust washers asap. Grab hold of the font pulley and see if you can move the crank fore and aft by more than a gnat's whisker. If you have an assistant, push the pulley back as far as you can, and get your assistant to then depress the clutch pedal fully (engine stopped of course!) See if you can see (or better, feel) any movement. An engine rebuild is not an absolute guarantee of freedom from thrust washer problems if the crank face has become at all worn or damaged before the thrust washers were replaced.
            That said, I'd be most surprised if that were the cause. The problem is much more likely to be found in the bellhousing. Could be a defective release bearing, or more likely, either a misaligned bearing carrier (perhaps caused by worn pivot pin and/or missing pivot pin bushes) or a faulty clutch cover plate.

            • Tapping when clutch depressed 

              Posted By : Julian Saul, 26-Jun-2007, 07:20pm

              I had a similar situation some time ago after having fitted a complete enew clutch assy.. The cure was found after slightly releasing the clutch slave cylinder bolt and moving the slave cylinder itself, as far to the rear as was possible, with the bolt in situ but not tightened! Having tightened the bolt, folowed by a quick test drive verified the cure!

              • Tapping when clutch depressed 

                Posted By : David Sibert, 26-Jun-2007, 09:22pm

                Dear Julian,
                
                Sounds interesting, so what do you think was tapping?
                
                Dave

            • Tapping when clutch depressed 

              Posted By : David Sibert, 26-Jun-2007, 09:18pm

              Dear Chris,
              
              I know I can't rule out thrust washer failure just because of an engine rebuild, but I can't even detect a gnat's movement on the crankshaft.
              
              I know that eventually I might have to delve behind the sump, but I'm trying to rule out everything else before I do so.
              
              The release bearing sounds like a possibility because even the slightest pressure on the pedal causes the tapping to start. I think I might change some clutch parts next - including the release bearing.
              
              Thanks for your help,
              Dave

    • Tapping when clutch depressed 

      Posted By : David Sibert, 26-Jun-2007, 09:20pm

      Dear Mark,
      
      From yesterday, I removed the fan belt and went out for a short drive.
      
      Still tapped.
      
      Sorry, but you don't win the coconut!!
      
      Many thanks for your advice though.
      Dave

      • Tapping when clutch depressed 

        Posted By : Peter & Mick Lewis, 27-Jun-2007, 02:59pm

        Dave as tapping is evident on very light pedal ,is there any vibration sensation noticeable , as this would add to the finger theory, and as your clutch is a direct operation and has no levers or gubbins in the operation ,noise and feed back would be
        more noticeable,, the ends of the diaphragm are normaly only linished to finish them off.
        as your actuation is unique are you sure there is nothing on the bearing carrier that could contact the diaphragm as you depress the fingers ??? and a couple of weeks of town driving should even out any runout noises, and in addition the direct operating slave in your scheme may be affected by misallingment due to bent engine back plate as it is less tolerant of errors and more for euro box tolerances just some thoughts Peter

        • Tapping when clutch depressed 

          Posted By : David Sibert, 27-Jun-2007, 08:55pm

          Dear Peter,
          
          I'm not sure of anything any more!
          
          Because I can't Identify any movement on the crank, I will take the chance and drive it for a couple of weeks without doing anything.
          
          If the tapping goes away of its own accord, I'll be very happy. If not, I will take your advice and take the clutch to pieces and have a really good look at it.
          
          Incidentally, now you come to mention it, there is no feedback (like pulsing of the pedal), and the frequency of the tapping sounds to me like one tap per revolution, rather than one tap every time a clutch finger goes past something.
          
          Anyway, Give me two weeks, and I'll announce the results.
          
          You have given me plenty to think about.
          Thanks,
          Dave

          • Tapping when clutch depressed 

            Posted By : Chris Taylor, 27-Jun-2007, 09:15pm

            It would be MOST unlikely for you to hear each individual finger. What I think was being suggested was either one rogue finger, or possibly either the diaphragm itself, or possibly the whole cover plate being not quite square to the flywheel or at least the face of the release bearing.
            If you cannot detect movement on the crank, please do NOT worry about thrust bearings. Sorry if I overstated the case, but a missing washer is VERY obvious, and you would definitely be able to detect serious wear before the point is reached where the washer can fall into the sump. Once you know what you are looking for, and check it from time to time (if you have any reason to be suspicious) you need never be caught out by it. The problem does exist, but should not be overstated as while it CAN happen (BTDTGTTS!), it certainly does NOT happen to every engine every five minutes!
            Please forget about your thrust washers now and enjoy your rebuilt engine!
            Whatever it is, the problem is almost certainly in the bellhousing. Nothing there is likely to suffer sudden atastrophic failure, so drive it and see if it gets better or worse, or stays the same. If better, you're laughing, if worse, you'll probably be able to find the problem more easily, but if it stays the same, you'll probably remain puzzled and frustrated, but your confidence that it's not going to go bang should grow.
            Even if something does go bang there, unless you knacker the gearbox input shaft (not likely) there's nothing too difficult or expensive to replace there, including the bellhousing itself.

            • Tapping when clutch depressed 

              Posted By : Peter & Mick Lewis, 27-Jun-2007, 10:18pm

              hi , yes agree run it for a bit and we can all listen out for the bang !! Pete
              ps ive looked at the supplier but web site under modification but will follow up the
              concentric throwout it seems an obvious solution to rods levers and ( tapping) peter

              • Tapping when clutch depressed 

                Posted By : Hugh Glossop, 28-Jun-2007, 10:51am

                sounds to me like simple thrust bearing failure
                
                hugh

                • Tapping when clutch depressed 

                  Posted By : Peter & Mick Lewis, 29-Jun-2007, 11:49am

                  as yours is a unique installation ,, I ment to mention that diaphragm clutches normally have the release brg. chamfered around the outside so that the outer diameter cant make contact the fingers somewhere beyond the raised end of the finger when half to fully depressed.
                  that can make some good noises and really ups the pedal loads,, but yours does not sound that compicated Peter