KenEvans Posted July 11, 2001 Share Posted July 11, 2001 Hi and help! There's something going on inside the bellhousing of my 6000 mile K series Supersport (light flywheel). It hasn't crept upon me but started suddenly last Sunday. As revs pass through 4000 the clutch pedal starts to tap the bottom of my foot followed by a long ccrreeeeeetttchhhh accompanied by lots of vibration. It stops when I place my foot lightly on the clutch. I get the impression the release bearing is initially bouncing off the clutch and then shimmeying like crazy (if that's how you spell it). I've increased the tension on the spring at the clutch pedal end which simply upped the revs at which it occurs a little. Does anybody have any ideas what might be causing this? Might I be able to rectify it using keyhole surgery techniques?...or are we talking about replacing the release bearing here (sob)? Ken Link to comment Share on other sites More sharing options...
KenEvans Posted July 11, 2001 Author Share Posted July 11, 2001 I noticed Steve Motts got loads and loads of replies about his vibrating knob!!! There's been lots of posts today (11th) so I hope mine doesn't get lost! Hellpppp!! Ken Link to comment Share on other sites More sharing options...
Peter Carmichael Posted July 12, 2001 Share Posted July 12, 2001 Unfortunately, they all do that sir. You must have an old one. The aluminium front cover (nose) of the six speed box doesn't support the release bearing carrier sufficiently and the nose begins to wear. The wear pattern means that the bearing whirls into position every time it comes into contact with the clutch, aggravating the wear situation. The bearing carrier itself starts to break down (you have got to this stage) and then the bearing is no longer held centrally as it is brought up into contact with the clutch and now it whirls significantly, sometimes not getting there entirely causing the vibration you feel through the pedal. There is a cure. But it needs the engine out. You need a new design front cover which extends a bit further and has a steel sleeve on the end. You need a new release bearing. It is an annoying engine out job for the sake of a ~£10 part. Link to comment Share on other sites More sharing options...
CHRIS CLARK Posted July 12, 2001 Share Posted July 12, 2001 Peter is right again. The release bearing is about a tenner and the new, modified front carrier with steel sleeve is approx. forty quid. Mine came from 'Road & Race Transmissions (Phil Stewart) 07736 333882 Link to comment Share on other sites More sharing options...
dba11 Posted July 12, 2001 Share Posted July 12, 2001 The newfront cover doesn't cure this problem, as I have had two release bearings go with the new front cover. All it seems to do is, make the release bearing last a bit longer. Daren. Link to comment Share on other sites More sharing options...
KenEvans Posted July 12, 2001 Author Share Posted July 12, 2001 Thank you Peter, Chris and Darren - the thing is it's not a six speed box and it's pretty well brand new having been built by me just last summer. I'd expect what must be standard production hardware to last much longer than this - it's only done 6000 miles after all. The only odd thing about the engine gearbox combination is that Caterham apparently ran our of new gearboxes when I ordered my car and I had to take a "re-manufactured" 5 speed Ford unit off them. Any more ideas? Link to comment Share on other sites More sharing options...
CHRIS CLARK Posted July 12, 2001 Share Posted July 12, 2001 Darren. Are you sure you're not 'resting' your foot on the pedal? Easily done in a tight 'K' cockpit!!! Link to comment Share on other sites More sharing options...
CHRIS CLARK Posted July 12, 2001 Share Posted July 12, 2001 Ken, I had heard that Caterham where unable to obtain new 5 sp. units. I guess this is the proof!! Link to comment Share on other sites More sharing options...
oilyhands Posted July 12, 2001 Share Posted July 12, 2001 Just because you dont have the 6 speed box it doesn't mean the release bearing isnt fubar'ed. In my experience they are of variable and sometimes questionable quality. The real pain is that the bearing itself is often not the problem,but rather the attachment between the bearing and carrier which can fracture if the bearing is not offered up to the clutch diaphragm entirely concentrically. I'm convinced that there is also a geometry problem with the 5 speed box and carrier also, this could be because often the long input shaft box is used and this is spaced 1 inch further back. This *may* have an affect on the bearing carrier efficacy. Oily Link to comment Share on other sites More sharing options...
dba11 Posted July 12, 2001 Share Posted July 12, 2001 Hi Chris, No, I rest my foot under the clutch on long journeys, or bend my leg so as the foot touches the side of the footwell. My last release bearing I have at home, and all that is left is a round bit of plastic with a bit of metal in places. This was still working (don't know how), but all the bearings and a big metal ring had disappeared!!! Daren. Link to comment Share on other sites More sharing options...
KenEvans Posted July 12, 2001 Author Share Posted July 12, 2001 Thanks for answering the question about resting my foot on the clutch Daren! Nope - I'm pretty mechanically sympathetic and wouldn't give the release bearing that sort of treatment. It sounds like the release bearing is heading towards being knackered though I always thought this showed itself up as a whine when you put it under load when dipping the clutch. It's strange that this racket and vibration occurs foot off the clutch at high revs and disappears with light foot pressure. No external or keyhole surgery fix then by the sounds of it. Does anybody from Caterham Cars have anything to say I wonder about this early failure? It's a shame they don't warrant my time to take the engine out as well as a £10 bearing. Ken Link to comment Share on other sites More sharing options...
dba11 Posted July 12, 2001 Share Posted July 12, 2001 Ken, The question seemed to be aimed at me. Daren. Link to comment Share on other sites More sharing options...
CHRIS CLARK Posted July 12, 2001 Share Posted July 12, 2001 It was just a thought lads! I must say that the release bearing doesn't exactly inspire confidence when you open the box does it. Too much plastic/glass reinforced resin for my liking!!! Link to comment Share on other sites More sharing options...
Rob Walker Posted July 12, 2001 Share Posted July 12, 2001 I can confirm that what Peter and Chris have said is correct however I would like to add that it is very important to centralise the bearing on its carrier before installation or the bearing will scuff away at the clutch fingures get hot and the the bearing separates from its carrier and waers a groove in the steel sleeve on the input shaft extension. It has happened to twice, Len Unwin said that this noise that was present before failure was caused by the lightweight flywheel I now know different. Link to comment Share on other sites More sharing options...
KenEvans Posted July 13, 2001 Author Share Posted July 13, 2001 Yes!! Len Unwin also told me following build that the clunk clunk clunk noise coming from the bell-housing at idle without the clutch pressed was normal on the Supersport/light flywheel. I actually got to like the noise because it made the car sound a bit more meaty at idle!!! So it was slowly knackering the release bearing and other things was it?? Link to comment Share on other sites More sharing options...
KenEvans Posted July 13, 2001 Author Share Posted July 13, 2001 sorry Daren - yes the foot-resting-on-the-clutch question was addressed to you Ken Link to comment Share on other sites More sharing options...
oilyhands Posted July 13, 2001 Share Posted July 13, 2001 The release bearing and carrier may not be overengineered but the same unit has performed relatively reliably in the Ford Sierra, sometimes for well over 100,000 miles. The problem is precison of assembly/fit rather than quality of componentry, at one time you could by a bearing with a sintered carrier rather than plastic/resin. I dont know if these are still available. Oily Link to comment Share on other sites More sharing options...
Lennie Posted July 13, 2001 Share Posted July 13, 2001 Thought I should defend my reputation. The noise you are refering to that can be heard at idle is the gearbox, as the gears take up the backlash. When the engine comes up to compression the piston trys to stop, but the energy stored in the flywheel overcomes this resistance.The lighter the flywheel the more this effect is exagerated, hence any play in the drive train is apparent, supersport cams can also have an effect due to the lumpier idle. As to the original question the release bearing is a problem because of a lack of support on the 'nose piece' and the fact the original Caterham items were aluminium. The new ones are longer and have the steel sleeve which has a tighter tolerance between it and the bearing and should cure the problem, except that the spring on the clutch pedal pulls the release bearing onto the cover plate, which has the same effect as resting your foot on the clutch pedal! A mod is to add another spring, opposite the exsisting one, onto the pedal to take the bearing away from the cover plate this also stops the pedal vibrating when the car is being driven. This can take some time to set up as it will determine the height of the pedal. On a seperate note a formula one car with no flywheel and very high compressions slows the car with a force of one 'G' when the throttle is lifted due to engine braking. Link to comment Share on other sites More sharing options...
Lennie Posted July 13, 2001 Share Posted July 13, 2001 Thought I should defend my reputation. The noise you are refering to that can be heard at idle is the gearbox, as the gears take up the backlash. When the engine comes up to compression the piston trys to stop, but the energy stored in the flywheel overcomes this resistance.The lighter the flywheel the more this effect is exagerated, hence any play in the drive train is apparent, supersport cams can also have an effect due to the lumpier idle. As to the original question the release bearing is a problem because of a lack of support on the 'nose piece' and the fact the original Caterham items were aluminium. The new ones are longer and have the steel sleeve which has a tighter tolerance between it and the bearing and should cure the problem, except that the spring on the clutch pedal pulls the release bearing onto the cover plate, which has the same effect as resting your foot on the clutch pedal! A mod is to add another spring, opposite the exsisting one, onto the pedal to take the bearing away from the cover plate this also stops the pedal vibrating when the car is being driven. This can take some time to set up as it will determine the height of the pedal. On a seperate note a formula one car with no flywheel and very high compressions slows the car with a force of one 'G' when the throttle is lifted due to engine braking. Link to comment Share on other sites More sharing options...
KenEvans Posted July 13, 2001 Author Share Posted July 13, 2001 Your reputation was never in question Len but it's great to see you taking an interest with such a thorough response :-) Thank you. I suspected there might be an external fix to this so I'll be experimenting with opposing springs this weekend. Regards Ken Link to comment Share on other sites More sharing options...
Lennie Posted July 13, 2001 Share Posted July 13, 2001 Sorry to disappoint Ken, but having read your initial query I think you will find that the release bearing is actually on its last legs and will need the engine to come out. The spring mod stops premature failure of the bearing as it holds the bearing away from the clutch plate when the engine is running. Can you imagine the grief it gets when it is spinning with the engine at maximum revs. When you take the engine out, check that the nose piece is the current spec. This is easily done - the new one has a steel sleeve on the end about 40mm long. Any problems just get back to me. Len Link to comment Share on other sites More sharing options...
KenEvans Posted July 14, 2001 Author Share Posted July 14, 2001 OK - thank you Len - I'll try the spring mod anyway to see if it alleviates it a bit, and then build myself up to taking the engine out during the next couple of weeks. Ken Link to comment Share on other sites More sharing options...
KenEvans Posted July 14, 2001 Author Share Posted July 14, 2001 Adding an opposing and equal spring to the clutch pedal seems to have "cured" it for the time being......no more ccrreeeeeettcchhhhhhhing noise :-) Hopefully that'll see me through to the winter when I'll be modifying or changing the engine for a bit more power. Thank you Len et al. Link to comment Share on other sites More sharing options...
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