Clutch Release Bearing

[Gary G]

What would be the symptoms on my Superlight if the above was going/gone?

[John Howe]

Work backwards from what the bearing does...

 

The bearing is pushed up against the clutch when you disengage. At that stage, from sitting minding its own business, it suddenly needs to "work" at the speed of the of the gearbox shaft, until the clutch is disengaged, at which stage it rotates at engine speed.

 

Assuming the release bearing has "gone" then you most likwely will still be able to disengage the clutch but the sound effects of the knackered bearing will be very obvious and the pedal should pick up viabrations from the sick bearing. If the bearing actually falls to pieces then viabrations and sound effect will be must greater and you will have instinctively turned the engine off.

 

Not an expensive part to replace, just a pain in the butt to do, as you will need to have the engine out to access the bellhousing.

 

JH

Deliveries by Saffron, the yellow 222bhp Sausage delivery machine

[SteveP]

Presumably a noise considerably different to and not to be confused with the lay shaft gears rattling about when the clutch is dis-engaged?

 

I find this noise rather disconcerting even though I know about it, it has been there since new and the car has only 1300 miles on the clock

 

 

SteveP

[John Vine]

Gary,

The symptoms I experienced on the two CRB failures I've suffered were, initially, an occasional squealing noise when depressing the clutch, which disappeared after pumping the pedal several times, and, finally, a metallic shrieking noise, like running a sanding disc against a metal plate.

 

it suddenly needs to "work" at the speed of the of the gearbox shaft

John, I'm assuming you're referring to the standard Caterham/Ford Sierra AB57 CRB? If so, there's been quite a bit of discussion recently that suggests the CRB should run in constant contact with the clutch-cover diaphragm fingers, held there by a pre-load of 80-120N. (This is the recommendation of the CRB manufacturer, INA). IMO, the Caterham set-up doesn't achieve this (at least, not on my 1999 1.8SS, where I reckon the pre-load is as low as 15N). I'm taking the engine out on Tuesday to fix the latest failure (plus install a 6-speeder while I'm at it!). I'm also applying a fix (thanks, Nick Green, for the basic idea) to increase the pre-load to around 100N -- more news later when I've finished the job. If anyone's interested, I'll be happy to describe my "solution".

 

JV

 

 

[Mark Durrant]

John

 

Please describe your solution as it looks like my new CRB bearing is showing early signs of failure after just 500 miles . I am just a little pi**ed off as the last bearing covered 12,000 miles and was OK when removed. I thought that by fitting a new one I was minimising the risk of a CRB failure in the immediate future

 

Good luck

 

Mark D

Su77on Se7ens

Avoiding the Kerbs

[John Vine]

Mark,

 

The basic idea is to increase the CRB pre-load substantially by replacing the existing single clutch-pedal return spring with two of the same size, but pulling directly on the clevis pin and along the line of the clutch cable. (I'm assuming that your car has the same set-up as mine and the standard clutch actuating arm.) So, proceed as follows:

 

1. Obtain two clutch-pedal return springs from Caterham. Note that the spring often supplied (p/n 1454217) is too small; you need to ask for springs that are 100mm long overall, with a coiled section 30mm x 15mm (listed as "brake pedal springs", apparently -- Darren will know

what to send).

 

2. Drill two 2mm holes in the top rear flange of the pedal box on the inboard side, just in front of the screw hole, so that they are in line with the clevis pin ends. These holes will be about 18mm apart and the inboard one will be about 3mm from the corner of the box.

 

3. Trim one end of each spring to about 30mm (that is, keep the straight bit), and make a sharp hook-shaped bend (25 deg) about 10mm from the end.

 

4. Insert these hooks into the 2mm holes from the underneath.

 

5. Make a full circular loop in the other end of each spring (so as to fit snugly over the clevis pin), ensuring that each spring (this is the tricky bit) is extended by 23-25mm when attached to the pin, and then trim off the excess spring wire.

 

6. Reassemble the pin and cable-eye such that one spring loop is under the pin shoulder and the other under the washer and R-clip.

 

7. Remove the original spring completely.

 

8. Replace the pedal box cover. This should hold the springs in place and prevent them dropping out in use.

 

My reasoning for all this is as follows:

 

At the clutch end, the mechanical advantage of the clutch cable over the CRB is about 2.5 (distance from CRB to fulcrum 110mm, and from cable to fulcrum 280mm). To apply a pre-load at the CRB of 100N (mid-point of INA's recommended 80-120N range), the cable needs to pull at 40N. So, assuming a frictionless cable arrangement, the combined pedal springs also need to pull at 40N along the line of the cable.

 

40N in imperial is 9lb (1N = 0.2248lb). Although Caterham quote the rate of the pedal spring as 7lb/in, I measured mine at 4.75lb/in, with each additional pound extending the spring by 1/4in. So, a 9lb total pull (4.5lb/spring) requires each spring to be extended by about 15/16in (that is, about 24mm). Apologies for the mixed units, but at least I'm following Caterham's own long-standing tradition!

 

I hope all this makes sense. I think my reasoning is OK, but if anyone knows better, please put me straight! However, I make no claims whatever that this "solution" actually works in practice (although I'm about to find out, and will report back). It may also contradict Caterham's own recommendations and practice, so you proceed at your own risk. However, judging by BlatChat posts, premature CRB failure does seem to be a 7 trait, and the main reason (to my mind, at least) is that the standard set-up doesn't apply sufficient CRB pre-load.

 

JV

[Rob Board]

Gary, another area to look at is the gearbox input shaft. When you come to replace your CRB, wth the box in neutral try and move the input shaft from side to side. If there is excessive play, then the input shaft bearing is suspect. This give the same symptoms as CRB failure as it allows the CRB to slop all over the place, hence the vibration and squealing. Then after time it causes the CRB to disintegrate. You replace the bearing, thinking that is what is at fault only to have it come back again. I do not know what excessive play should be, but speak to Phil at RR transmissions, and he will tell you. Also the theory of what John Vine says about the pre-load is also correct. When my CRB started making a horrendous noise after 800 miles(new factory built roadsport), I researched the preload issue, hence the figures JV quotes. However, when caterham showed me my CRB that they replaced it looked perfect, so who can tell. They also changed my Gearbox and clutch assy, and some 3000 miles on all is great, so I am well chuffed with what they have done. Obviously time will tell.

There are many owners who have done thousands of trouble free miles on their CRBs, but some are unlucky. Sooner or later someone will get to the cause so hope this advice is of use, and good luck john with your "fix". Rob

 

[Gary G]

Thanks for your replies.

 

My symptoms are:

 

Squealing noise accompanied by a low pitch "growling" noise, but only when:

1) At low revs/idle and;

2) When the engine is warm

 

However, it doesn't happen all the time. It normally starts when I've been giving it some welly. It didn't happen yesterday when I did 30 motorway miles at a leisurely pace.

 

I don't have any other symptoms such as vibrating clutch pedal or anything like that.

 

 

If it is the CRB, does anyone know the best place for me to get it fixed? I'd prefer it to be sorted with the additional mods mentioned above to prevent re-occurence, but I will not be able to do the job myself.

 

Also, what are the implications if I leave it for a few months?

 

 

[John Vine]

Rob: Yes, I was indeed quoting the results (INA figures) of your excellent research, and many thanks for your efforts!

 

as it allows the CRB to slop all over the place

You puzzle me here, though. The CRB slides up and down the sleeve through which the first motion (input) shaft passes, and doesn't come into contact with the shaft at any time. As the sleeve is rigidly fixed to the front of the gearbox, I can't see how any sideways movement in the shaft can affect the CRB at all (besides which, the spigot at the front end of the shaft should be firmly located in the end of the crankshaft).

 

Gary: The squealing could indicate a knackered CRB, but only if it occurs when you depress the clutch pedal. I guess the growling at idle could well be slack in the input shaft or idler gears (and may be entirely normal). As far as the CRB is concerned, mine continued squealing for some weeks (months, even) before it reached the metallic scraping stage (caused by the CRB assembly completely disintegrating, and the ears on the clutch actuating arm rubbing against the bearing housing). I also seem to remember the squealing occurred only when the engine was hot (like yours). As for getting it fixed, any garage should be able to replace the CRB for you, and they could apply my "fix" too (if that's what you want) once they have the springs. But, as I said earlier, I make no claims that it is really is a fix. It just seems to be the logical extension of the debate to date. My discussions on the subject with Caterham have been inconclusive so far. They agree that a pre-load is necessary, but suggest that the standard set-up just about (at 76N) provides sufficient loading (which is where we begin to differ, of course, as I can't reconcile their spring rates with their load measurements!). FWIW, I was talking to the local Ford dealer Parts Manager the other day. He said the (Sierra) CRB should not be run in constant contact with the clutch cover springs. When I pointed out that the CRB manufacturer said it should, he went rather quiet, and then said "well, you learn something every day".

 

JV

 

 

Edited by - John Vine on 5 May 2003 18:22:00

[Bare]

Dunno where this"in constant Contact" stuff comes from. but In my Automotive experiences, beginning with Campainging a Cooper S back in the 60's.. Throwout bearings in Contact with the clutch die early... Period.

I'd seriously rethink that bit of Info .

[Gary G]

John,

 

The growling is in addition to the normal other growling noises from the things you mention.

 

I think my best bet is to see if the squeal stops when I release the clutch...

[Dave_H]

Bare:

 

This “in constant Contact" stuff came from the manufacturer of the bearing…

 

Dave

 

[John Vine]

Bare,

As Dave H says, the manufacturer (INA) recommends constant contact (in fact, their Technical Engineering Support people say it's essential if premature CRB failure is to be avoided due to excessive heat build-up). The CRB in question is the same one as fitted to the Ford Sierra. Ford apply the necessary pre-load by means of a self-adjusting cable tensioner. Given that both INA and Ford specify constant contact, I think I'll go with their advice.

 

JV

[Mark Durrant]

John

 

Thanks for your advice. I will give this a go as my symptons are similar to yours and I do not want to take out the engine again. I do not believe the problem to be with the input shaft, only 12k miles and no problem with the previous bearing. Funnily enough despite giving the car plenty at Cadwell yesterday the CRB behaved itself

 

Mark D

Su77on Se7ens

Avoiding the Kerbs

[MikeE]

I think mine might be on the way out on my 2000 Superlight with 9,000miles on the clock (I get an intermitent 'squeal' when I fully depress the clutch)

 

I'm going to change mine after my next track this weekend.

 

Can anyone tell me how long it takes to remove the engine (do you have to do this?) and split the bell housing?

 

Also are there any instructions available?

[John Vine]

MikeE,

Yes, you do have to take the engine out. The whole job takes anything from two hours to a day, depending on how quickly you work. It's not difficult, just fiddly. Apart from an engine crane, you'll need an assistant for the crucial bits (sliding engine forward, etc) so as to guide the gearbox tailpiece (with its vulnerable attachments like reversing light switch and speedo drive) past the chassis.

 

The process is pretty much the reverse of the Assembly Guide instructions (if you have them). Alternatively, I guess Caterham could be persuaded to send you some photocopies. Anyway, these are the main steps (for a 1999 1.8 Supersport, with Apollo):

 

Remove gear knob

Remove transmission tunnel cover (two selftappers behind seats)

Remove gear lever

Disconnect battery (and remove for extra room)

Remove air cleaner

Drain coolant

Remove LHS engine bay bracing strut

Remove exhaust pipe

Remove exhaust manifold (you may need to delay this until the engine is raised about 9")

Disconnect heater hoses at valve

Disconnect fan

Disconnect radiator hoses and remove radiator

Disconnect submarine pipe at rear

Disconnect header tank overflow pipe at engine end

Remove header tank and attached hoses as complete assembly

(Leave Apollo tank and hoses attached, but cut all tywraps)

Remove pedal box cover

Disconnect and pull out clutch and throttle cables from box

Disconnect various engine loom connectors

Disconnect lead to charcoal canister

Remove ECU from mountings and disconnect plugs from back

Disconnect rubber breather tubes from inlet manifold

Disconnect fuel return line (black) from inlet manifold (and plug it to prevent petrol leak)

Disconnect fuel feed line (copper pipe) at rear of engine (and plug it ditto)

Disconnect speedo cable at rear of speedo (knurled nut)

Disconnect earth strap from O/S engine mount

Jack rear of car as high as possible (2 feet or so) and insert axle stands

Raise front wheels onto blocks (say 3") to allow crane access

Remove rear gearbox mounting bolts (2)

Place engine sling/straps round engine (I use ropes, divided between inlets 1+2 and 3+4)

Take up slack

Remove both vertical engine mounting bolts

Lift engine an inch or so, and then remove both engine mounts

With assistant under car, lift engine, sliding it forward until propshaft detaches from gearbox tailpiece

Insert plastic plug (if you have one) into tailshaft to prevent oil leaks

Lift out engine/gearbox and rest on bench

 

BINGO!

 

On the bench:

Remove starter

Detach clutch cable from actuating arm and remove

Undo bellhousing bolts

Slide bellhousing/gearbox back, keeping it well supported and level

Pull actuating arm off pivot and remove arm/CRB as unit

Remove CRB (press in two metal clips at rear)

Insert new CRB (don't lubricate the CRB slider/sleeve)

 

Reassemby is pretty much the reverse.

 

Torques:

Bellhousing bolts: M12: 61Nm/45lbft, M10: 34Nm/25lbft

Starter: 34Nm/25lbft

Gearbox mounting plate to chassis: 16-20Nm/12-15lbft

Exhaust manifold: 34Nm/25lbft

Engine mounts (to engine): 34Nm/25lbft

Engine mounting rubbers: 16-20Nm/12-15lbft

Engine mount (to rubbers): 61Nm/45lbft

Engine bay diagonal: 34Nm/25lbft

 

I think that's about it. No doubt, if I've missed something, someone else will be along shortly to put me straight. Good luck!

 

JV

 

 

 

 

 

 

 

 

 

 

Edited by - John Vine on 7 May 2003 12:46:59

[John Vine]

An update...

 

I've just removed my old CRB. I have to say, it looks a lot fitter than last time, but still shows signs of overheating (pressure face all coppery patches and polished). The bearing housing also slides around quite freely on the plastic carrier (the new one can be made to move, but it's very much tighter), and it rotates fairly easily too. I don't think it's supposed to do that, but merely move to centralise itself on first contact, and then remain in that position thereafter. (I've just heard from Nick Green that, according to INA, this excessive sliding movement is symptomatic of overheating due to insufficient pre-load.)

 

I now think I know what the squealing noise is. I reckon it's caused by the bearing housing

moving off-centre, which then causes the pressure plate to rub eccentrically on the diaphragm fingers (not unlike a rotating floor polisher whose mats are off-centre). Pumping the pedal eventually re-centralises it, and peace and quiet ensues. I'll mention my hypothesis to INA and see what they say. If I'm right, then the squealing is a clear (but early) sign of overheating, itself caused by insufficient pre-load. If ignored (and no attempt is made to increase the pre-load -- although, by then, it may be too late), the CRB is likely to fail catastrophically (in my experience, by disintegrating into several pieces, with subsequent damage to both guide sleeve and diaphragm fingers).

 

More news later.

 

JV

 

[MikeE]

John you are a star thanks very much for the description.

 

cheers,

Mike.

[Rob Board]

John,

 

Yes I appologise for my technical error earlier. I should have added that a dodgy input shaft bearing will only cause the crb to slop about if the crb manages to slide off the end of the guide sleeve and come ito contact with the shaft itself, which I beleive has happened in the past. Sorry, fingers working faster than brain 😬, or is that the other way round? But I do know that a disintegrating input shaft bearing will give the same squealing noise and vibration as a knackered crb. Anyway well done on the progress so far. When you have spoken to INA regards your current findings with your crb do email me! Hopefully you are now nearer to a "fix" for those who do experience problems. As I say, mine has been fantastic since Caterham changed the box etc, so I should not have to change the clutch/crb for some time. When I do to aleviate any future snags I am going to fit a concentric hydraulic clutch which should put the problem to bed for ever! Good luck once again. Rob

[R2D2]

Are you sure that the CRB needs a pre-load rather than just being in light contact so that it is rotating allof the time.

 

I can understand why trying to accelerate the rolling elements from standstill to engine speed at every gearchange would cause skidding and hence damage but I don't think that a specific amount of pre-load should be too important.

 

I think that old style CRB s were often carbon faced rather tahn rolling elements and it is this type that would't like continuous contact.

[KenEvans]

This "constant contact" advice doesn't sit comfortably with Len Unwin's recommendation to fit a spring equally opposite to the standard clutch return spring at the pedal, which is what I've done.

 

So I am now confused which is not difficult.........

[mic]

I know this is not quite the same but all new ford concentric release brgs run in constant contact

[John Vine]

Chris: It's not so much my being sure, rather the CRB manufacturer (INA). They are adamant that a pre-load is required, and the recommended range is 80-120N (which is a "light" load, I suppose, but sufficient to ensure continuous contact).

 

Ken: Well, I agree (or, rather, I did). Len's given me good advice in the past, and I even applied his counter-spring "fix". However, if I had to say who I thought knew more about this CRB, Len or INA, I think I'd have to plump for INA. I think Len was under the impression (as I was at the time) that CRBs were not supposed to run at crank speed (indeed, I think that that was exactly how they were designed to work, say, thirty years ago).

 

I'm about to send my two failed CRBs to INA for their expert comments. I'll post the results here when I get them.

 

JV

 

 

[Mark Durrant]

John

 

I have just applied your fix and I'll let you know how I get on. I would also be interested to hear what INA have to say about your failed CRB's.

 

Thanks again and fingers crossed that this works.

 

Mark D

Su77on Se7ens

Avoiding the Kerbs

[John Vine]

I've just heard back from INA (Stewart Davies), with comments on both my failed CRBs. The first one was so wrecked, apparently, he couldn't say what had caused the failure. About the second one, he said:

 

Observations:

 

"Bearing face is polished and shows discolouration"

 

"Signs of grease egress from bearing, at the interface between the bearing and the plastic housing"

 

"Bearing can be moved in a radial direction around the plastic housing with relative ease"

 

"Bearing still operates in a smooth, noise-free condition"

 

"Uneven contact pattern observed where clutch fork operates against the [plastic] housing"

 

Conclusions:

 

"Failure can be attributed to insufficient bearing pre-load resulting in skidding between bearing contact face and the clutch cover. This would lead to heat generation (discoloured contact face) and subsequent grease loss due to the elevated operating temperatures"

 

"We understand that this application has no pre-load feature. We do not have any information on this application to verify the installation parameters for our bearing"

 

"The ease with which the bearing can be moved in a radial action around the plastic housing can be attributed to the low pre-load. This feature is designed to locate the centre of the clutch and remain in this location for the remaining life of the clutch. It is not designed for repeated adjustment"

 

"The uneven contact pattern observed on the back of the plastic housing could be attributed to poor fork alignment, which results in uneven contact of the clutch bearing. This sometimes can be felt on the clutch pedal when the foot is applied lightly"

 

"The bearing will operate more effectively when a pre-load of 80-120N is applied"

 

 

Well, this was generally what I expected, but the comment about uneven fork contact is intriguing. When I replaced the first CRB (Oct 2001), the fork "ears" had been rubbing directly against the back of the metal bearing housing (the plastic had worn through), and were partly worn away. I didn't replace the fork as there seemed to be plenty of metal left. Maybe I should have? Also, the tips of the diaphragm fingers were worn and shiny.

 

Anyway, this time, I've replaced the clutch cover, fork, CRB and guide sleeve (as part of the 6-speed box), so all contacting parts are now pristine.

 

I called Stewart to discuss things. I pointed out that, in fact, the 7 had some preload rather than "none", and I described the pedal spring. We talked about ways to apply a pre-load. It seems the Caterham set-up is pretty crude (having no mechanism to maintain a constant pre-load as the clutch wears, or to mitigate the effects of clutch-riding). He agreed that my proposed springs should help, but that they'd need occasional adjustment to allow for clutch wear and cable stretch. He added that the typical clutch operating force was 800-1600N, so a pre-load of 80-120N was insignificant in operating terms.

 

He felt the squealing when the pedal was pressed was definitely an indicator of pending CRB failure, and was most likely due to the metal housing rotating against the plastic carrier (rather than my suggestion that the CRB was off-centre, and rubbing eccentrically against the fingers). He thought the fact that the squealing was apparent only when the engine was hot bore this out, and that pumping the pedal "stuck" the metal/plastic surfaces together more firmly.

 

So, there we have it! I'm now confident that my (that is, Nick Green's) fix design will do the job. I'll just have to wait and see.

 

JV