Major clutch issues, anyone seen this before?

[sailorbob]

My suspicion is that the pressure plate fingers are too short but, setting that aside, is it possible to fit the friction plate backwards and could that be the causing a restriction to the movement of the diaphragm spring resulting in the fingers being forced past the thrust bearing face when the clutch pedal is depressed?

[Lotusfab]

Does the friction plate fit the splines properly and is it lightly greased? The new plate on mine is  marked gearbox side

[Steve4012]

21 minutes ago, sailorbob said:

My suspicion is that the pressure plate fingers are too short but, setting that aside, is it possible to fit the friction plate backwards and could that be the causing a restriction to the movement of the diaphragm spring resulting in the fingers being forced past the thrust bearing face when the clutch pedal is depressed?

It's clearly marked gearbox side and was correct. 

 

13 minutes ago, Lotusfab said:

Does the friction plate fit the splines properly and is it lightly greased? The new plate on mine is  marked gearbox side

Yes fitted properly and greased splines and a small coating on bearing surface too. All packaged up and will be sent back to SJ and see what Steve comes back with. 7.3mm larger spline diameter between old and new with both off the car in a relaxed state seems a big difference. 

[Lotusfab]

On close inspection I found the fingers on the old pressure plate sat closer together when off the flywheel. They have weakened over the years. The new one the springs are better and when not in the flywheel the fingers sit much higher. It's possible mine may be very close when I bolt on the new plate. But yours being a slightly different type seems to me to have an excessive gap,

[TAR]

going back to your first post, 18mm may be too small a measurement.

[Steve4012]

Hi Tim. 

18mm was the amount of movement on the pushrod. I have the correct 22mm of thread showing from the lock nut. 

[MrDangerUS]

When replacing any component of the clutch actuation circuit, the system has to be bled.
Very effective and time saving method is to install a Speed Bleeder valve, http://www.speedbleeder.com/

and bleed the slave cylinder with its back side up. It is a "one man operation".
If 0.70" dia MC is replaced with 0.625" dia cylinder, then the push rod has to be made longer at the pedal clevis. 0.625" MC reduces the push force on the pedal and requires a longer stroke.
.

[ramjet]

Other than plugging a website for a product which, as far as I could see looking at the website, is only for brake systems, how does your post assist with the issue that Steve is having?

[Gis]

Steve, what was the cause and final resolution of your clutch issue then? I experience a similar issue of the release bearing being suspect of centre and causing clutch release issues and judder. My fork has excessive play too, seems too much. It’s perfectly normal at times but suddenly goes into judder and incomplete release. It’s a fairly new clutch (2 years old) and worked perfectly until a couple of weeks ago. Had the box off verified nylatron washer and spigot bearing in place. So your findings might give me some good clues and where to look next. 

[robertcosta]

The clutch pressure plate fingers need to match the bearing type.

[Steve4012]

Hi Gis,

I haven't posted a completion to the thread because it's still not right. I think the minimal tolerances of the first clutch kit from outer release bearing to inner clutch splines caused the complete mis alignment as originally posted but maybe it wasn't the only fault. I've since fitted a different pressure plate and bearing (matching characteristics as required) and the clutch engages and disengages correctly. However I can still feel a judder through the clutch pedal sometimes, only when I'm pressing the pedal, even though the clutch does work. I also have a squeek at tickover which disappears with the slightest touch of the clutch pedal, suggesting the release bearing but it feels smooth and quiet when manually turning and is brand new. I didn't want this so I've taken it all apart again. The way I'm thinking is that there is no excessive crank movement and the engine is recently rebuilt so that's ok. The gearbox was fine before removing first time, so I'm completely going through and checking everything in between the two. The only thing that hasn't been renewed is the flywheel so I've had Pete at PNM grind that for me. 

I've just got that back so over the next couple of weeks I'll systematically check and refit it all and go from there. 

[Gis]

Thanks Steve. I have a similar issue but it might be caused by something else. I had a perfectly good 2 year old clutch until a couple of weeks ago. My symptoms started with early clutch engagement and got progressively worse with pedal judder and difficulties to engage gears, sometimes. I initially put it down to a contaminated clutch friction plate (leaking main crank oil seal) so I opted to take the box off, change the seal, clean the flywheel and pressure plate and replace the friction plate with a new one. Turned out that friction plate didn’t look contaminated. Swopped it nevertheless and cleaned flywheel and pressure plate. All that done, the clutch worked normally for a very short time, 10 minutes into the first test drive all the problems suddenly reappeared. It felt as if something suddenly went out of alignment. Just barely managed to limp home. Current state now: The clutch separates ok without the engine running. All gears engage cleanly.  When the engine turns, I can now hear mechanical noises from the clutch pressure plate, especially when the clutch pedal is depressed. Gear engagement no longer possible with engine running. Stroboscope doesn’t show any obvious misalignment of the release bearing vs the fingers. I now suspect a failed  pressure plate or a failed release bearing. Both of which looked ok when I had the box off. So my next step is to take the box off again and replace the whole clutch assy for a new set with the later curved fingers (current set has flat fingers) and corresponding release bearing. My input shaft looks ok, the spigot bearing is in place and so is the nylatron ring and hardened sleeve. The input shaft circlip and spring is in place and can be felt when pressing the input shaft backwards. The input shaft has some angular play with the box off  which I assume is normal. The clutch fork has a large amount play as said before so I’m gone check on that and replace the pivot pin on it and check for excessive wear on the clutch fork pivot ball and replace it if necessary. Flywheel looked good and clean when I had it off. All actuating hydraulics are correct and fully bled. So box off again and new, complete clutch assy in is next, keeping my fingers crossed that this will resolve the issue. It feels like a wild goose chase for now. The effort involved to get the box off is a pita but has to be done. Will keep you posted. Comments and views welcome, as always. We live and learn..

[Gis]

2 hours ago, Steve4012 said:

I've just got that back so over the next couple of weeks I'll systematically check and refit it all and go from there. 

Good luck with your next steps btw. Hope it works out for you.

[drdoom]

Any chance this is a case of failing crankshaft thrust bearing? 

[Steve4012]

You're right to ask and I've thought this also. The engine was rebuilt just prior to me buying it by Pat Thomas, a well known Lotus Specialist, now retired and I trust the job was done correctly. I've had the sump off to reseal and the pistons do indeed look brand new. Also I've tried to move the crankshaft now I have the flywheel back off and can't feel any movement at all. I didn't want to pry too hard but I'll see if I can get the required tolerance play before I put the flywheel back on. 

[Gis]

On 08/07/2019 at 00:07, Steve4012 said:

Clutch always bit high with old and new clutch and the pedal was set as low as the thread on pedal would allow so I measured the throw of the slave pushrod and it was 27mm

Steve, I wonder how do you get so much travel/throw at your slave pushrod? Looking at the OEM master and slave setup in our cars (master 5/8” bore, slave 7/8” bore), the fluid volumes and a (measured) full master stroke of about 37mm, this translates to a maximum stroke of about 19mm at the slave. This is also what Steve/SJ refers to I Guess. Is your master cylinder different with a larger bore and/or delivering more volume? That might have contributed to your issue, overextending the pressure plate diaphragm fingers and even getting them to the point of contact with the friction plate centre hub. The friction plate hub can be seen in your photo and the fingers are wedged in between the hub and the release bearing. 

[Steve4012]

I'm not sure the bearing is on the friction plate hub Gis, I think that image just makes it look like it. The original problem (or one of them) was the bearing and splines on the pressure plate had a tiny tolerance. Things have moved on though, the problem is no longer the bearing slipping through now I have a different pressure plate and bearing, just I have an unpleasant judder through the clutch pedal when depressed. The clutch is back on with a newly skimmed flywheel, now I'll get the gearbox back on hopefully it'll be OK. 

[Gis]

Yes, it might just be the angle the picture was taken. Judder is not good. It means that the release bearing is off centre. Which will likely lead to its failure. I took the box off yesterday and what if found was very similar to your case. A cracked release bearing. I had juddering too. My prime suspect is the pivot ball point and corresponding contact face on the fork. I had wear on both. There is also wear on both fork ends where the release bearing sits. Probably normal. I then installed the new clutch (different type with rounded fingers and flat bearing face), new release bearing with new clips and cleaned up the whole system. Moving the fork up and down, I noticed that the bearing kinda slides off the fork on the extreme upper side. That did not look right. That said, this is on the fully extended max position. I doubt that the fork ever reaches that position in normal service life. With 19mm push on the slave side and a reduction lever (fork) in between the max bearing movement in input shaft direction is probably 12-14mm max. Anyway to make it short, my prime suspects on my car are the pivot ball and fork for now. The fork is nla unfortunately (unless somebody in this forum knows a source), the pivot ball is available. Might have to swop those next or find a way to work the problem if the judder comes back. Will keep you posted. 

[Gis]

Here’s an update. Installed all the gear around the box. With the order I placed for a new clutch I also ordered a few more bits as backup to the hydraulic system. For some reason (intuition maybe) I also ordered a new slave pushrod. Guess what? The new one is a whopping 1” shorter than the one I had in my car... as a consequence, my old release bearing has been literally squashed to death... I was always wondering why I could not get to 22mm exposed thread at the fork without strange noises from the back. This is the reason. I was running at 16mm since I bought the car, changed clutch when I did the belts 1.5 years ago. This was a failure waiting to happen. Never looked at the hydraulics other then bleed them. I really wonder where that long rod came from. Shoddy maintenance most likely. Well, the new setup is now in and seems to work fine, 22mm exposed thread, no strange noises, no juddering. Clutch feels normal. Next is an extended drive to confirm it. Steve, perhaps you wanna check the length of your pushrod too and tick that box. 

[Steve4012]

Great to hear yours seems sorted Gis. I've just measured the pushrod and I have the shorter one already. I'll try and finish up by tomorrow and see what happens. 

[dsvitesse1]

9 hours ago, Gis said:

Yes, it might just be the angle the picture was taken. Judder is not good. It means that the release bearing is off centre. Which will likely lead to its failure. I took the box off yesterday and what if found was very similar to your case. A cracked release bearing. I had juddering too. My prime suspect is the pivot ball point and corresponding contact face on the fork. I had wear on both. There is also wear on both fork ends where the release bearing sits. Probably normal. I then installed the new clutch (different type with rounded fingers and flat bearing face), new release bearing with new clips and cleaned up the whole system. Moving the fork up and down, I noticed that the bearing kinda slides off the fork on the extreme upper side. That did not look right. That said, this is on the fully extended max position. I doubt that the fork ever reaches that position in normal service life. With 19mm push on the slave side and a reduction lever (fork) in between the max bearing movement in input shaft direction is probably 12-14mm max. Anyway to make it short, my prime suspects on my car are the pivot ball and fork for now. The fork is nla unfortunately (unless somebody in this forum knows a source), the pivot ball is available. Might have to swop those next or find a way to work the problem if the judder comes back. Will keep you posted. 

Hi, I cannot imagine the fork and/or pivot ball is causing the problem. It is self centering, even with worn it will allways center. If needed I have forks. Never, never seen any problem with it. The release bearing has long guiding sleeve and will stay centered aswell.

 

cheers,

 

Harry Martens

[Gis]

22 minutes ago, Steve4012 said:

Great to hear yours seems sorted Gis. I've just measured the pushrod and I have the shorter one already. I'll try and finish up by tomorrow and see what happens. 

Thanks. Hope it works on a Long drive too. Hope you get yours sorted soon too. @dsvitesse1, Harry, thanks. Good to know

[DaveyT]

Hi Steve, 

back in 2016 (i found the thread looking for clutch help), you mentioned you are using a landy MC for your clutch.

did you check the bore size?    I ask cos Ive just replaced my brand new bearmach (STC100500 - quite possibly using that recommendation) with a Lotus one from SJ, and I noticed the bore size is larger on the bearmach. This would explain why you were getting 27mm throw at the slave, which could have been responsible for excessive force at the clutch plates? 

doesnt help with the mismatched diameters I dont think, but may be worth a check. I’ll measure my bearmach later for you.

[DaveyT]

^^ SJ supplied MC - 5/8 bore (15mm), my supposed landy replacement measures at 19.2mm , nearer 3/4”.

STC 500100, not 100500....

Hope you get it sorted.

[ekwan]

On 08/07/2019 at 19:06, Steve4012 said:

Thanks all for your input, it is much appreciated. The gearbox is back off and I hopefully have an answer. Both bearings measure the same at 58mm OD. The gap between the splines is indeed smaller on my original pressure plate. 49mm as opposed to 52.7 on the new one. So I have an overhang of 4.5mm either side on the old set up and only 2.65mm on the new so barely on the outer edge of the bearing. I'll email Steve at SJ the pics below and see what he says.

The clutch pressure plate had been replaced with the ones with curved fingers and a different release bearing. Would it be more prudent to fit the latest replacements?