New clutch definitely required

[Fast28]

After experiencing a slipping clutch in the S4s a few weeks back it's been hard graft at weekends getting the gearbox off and getting the necessary parts ordered.

Luckily during my prior recommissioning of the car I had already addressed the need for quick removal of the boot floor by removing the previous repairs done by garages who had obviously come up against seized bolts in rusty rivnuts in the past by replacing them all with labour intensive locknuts, bolts and washers. I installed jack nuts and stainless bolts so everything came apart easily. I took the opportunity to replace the gearshift cable ball joints and those on the translator arm, removed the exhaust, good opportunity to replace the left exhaust rubber mount which was some lash-up using a universal rubber isolator. The three bolts holding the bypass valve to the down pipe where cut off and bypass valve removed with the intention to replace it with PNM's spacer; the rest of system having previously been removed so it was really the last piece to go. Unfortunately removing the downpipe revealed that the cat was rattling badly and probably most of the cat fell out in distorted lumps. The engine had obviously had a fuel injection problem in the past and ended up melting the cat 😦. Took the exhaust mounting frame off and gave it a good clean up and repainted it with high temp paint. Disconnected the lower suspension link arms, pulled back the inner CV boots and was greeted with 27 year old liquefied CV grease 😝. Jacked the car up, grabbed each wheel and pulled it outwards releasing the driveshaft spider out of the yoke assemblies as recommended here on the forums 👍. Got the gearbox mounts unbolted, bell housing bolts off and shuffled the gearbox back, it needed a bit of persuasion with a pry bar but once moving it came away okay. I wasn't really satisfied with having the gearbox hanging around so I ended slipping it out under the back of the car.

On removing the gearbox, the clutch fork was no longer held to the pivot point as the rivet holding the spring retainer had long since disappeared. The release bearing was the wrong one, it was for an S4 not an S4s although an S4s clutch was fitted. Also the slave cylinder push rod had in the past been replaced with a 128mm long item in place of the stock 100mm rod, probably to counteract the shorter S4 release bearing!

 

The friction disk was worn down to 6.0mm (notes say 5.9mm useful life) and due to slipping the flywheel had taken a beating also, all this in under 11k miles as it was replaced the first time back in 2007.

 

I had to replace the crank sensor as that had got hot from the clutch and expended into the mounting hole necessitating in brute force to extract it and unfortunately breaking the top off, found a replacement Bremi 60391 which is a cross-referenced part for the orignal GM part number at less than half the price.

 

Upon removing the flywheel I noticed oil on the back of the flywheel and was eventually greeted by this...

So clutch parts list so far consists of the following: -

PNM's S4s clutch kit

S4s release bearing housing complete.

clutch fork spring

Rear main seal

rear main seal panel gasket

Spiggot bearing

resurfaced flywheel

Oh and just for good measure one of the above button head socket bolts rounded out, these were held incredibly tightly by Loktite so that looks like next weekends task while I wait for the flywheel to be resurfaced. Found a fairly local machine shop that seem to know their stuff and knew a few things about the Renault gearbox, link below.

https://www.kmbengltd.com/

 

Edited July 5, 2022 by Fast28

[Sparky]

Proper job and excellent write-up!

[Erikl]

I noticed that your parts list does not include the proper length push rod for the slave to fork.  Will you just cut down the old one?  Or is there enough adjustment at the slave.

What do you think was causing the slipping?  Oil from rear main and possibly S4 release bearing geometry?

Good catch on all those wrong parts!  I would never have figured all that out.  I will be very vigilant when I do my clutch based on your excellent write up!  Thanks!

[Fast28]

Hi Erik, before I started to take parts off I reduced the slave push rod length to 100mm to see what difference it made as both clutch pedal and the push rod abutment screw were set correctly to the Esprit service notes. As it happened with a 100mm push rod I could no longer select any gear, I believe if I had the correct release bearing fitted which would have given me the extra clutch disengagement I maybe would have been able to select gears and even use the clutch again.

[Fast28]

Well after one hot weekend the new clutch is in! 🥵

Re-ground flywheel and new pilot bearing as well as new rear main seal with gasket and sealant.

Working out how to get the axle spiders back into the yokes was an interesting battle as I remembered I had disconnected them with the gearbox released from the engine before but with the engine now bolted up it was much harder. Worked out the best way was to jack the rear of the car up, pull the wheels out as far as I could and chock them up with plywood boards, then lower the car gradually and the wheels slide out further as the plywood slides across the floor which gives enough clearance for the axles to be re-assembled. Jack back up and the spiders fit back into the yokes.

Just to be absolutely sure about the release bearing sitting correctly on the clutch fork I used a cheap eBay endoscope to peer inside the gearbox and satisfied that it was bolted the rest of the parts back in place. Used my 100mm cut down slave pushrod but I cannot select any gears 😦, the clutch does not want to disengage with such as short pushrod (previous workshop had fitted a 128mm pushrod but it was preloading the clutch as it was firmly held between the abutment screw and slave which probably caused the premature clutch wear. I've checked the clutch pedal position which is spot on between 175-180mm, I've got 12.5mm on the abutment screw, no leaks and the clutch pedal after a few pumps feels infinitely better (lighter). Either I need to bleed the hydraulics more or use a longer pushrod?

Here's a video clip of the push rod in action, can someone confirm I have enough travel?

S4s slave push rod

I found an interesting thread back in 2011: https://www.thelotusforums.com/forums/topic/42610-anyone-ever-had-their-flywheel-machined/#comment-360469 where lotus4s  had said he had seen cases where for no reason he had to use longer pushrods on 2 cars, maybe the reason mine was fitted with a longer pushrod?

 

 

 

[Erikl]

Vid not working for me. 

Seems like I have read about clutch arms fatiguinf and flexing?  or could the incorrect arm be installed?  Hopefully an easy fix after all that work.

[Fast28]

Hi Eric, I think it depends on your browser permissions. You can try and download the linked file, that seems to work for viewing on phones.

The clutch fork arm looks straight and original, in fact I removed all the surface rust, inspected it and painted it to help protect it before refitting.

[Chillidoggy]

If you’re 100% sure there’s no air left in the system, and you’ve got rid of the red hose, check the clutch master cylinder is the correct bore (0.7” I think), and also the slave, while you’re at it.

The clutch fork will of course push the push rod and piston back into the slave cylinder at rest, but not necessarily all the way to the forward end of the cylinder.

The slave cylinder piston position is determined by push rod length, that’s what the adjustment figure is for. Push rod travel will always be the same as long as the cylinder bores are correct. And, within reason, push rod length is not actually critical, a few millimetres from spec either way won’t make any difference. I hope that makes sense, because I might have had one or two cold beers….🍻 or more.

Presumably the flywheel was within the thickness spec post grinding?

[tomcattom]

Nice work Simon.

Plenty of useful reference information for me there when I tackle the drivetrain on mine over the coming winter.

[Fast28]

Ooh, found out @Cushingwho had the same pushrod as me..

https://www.thelotusforums.com/forums/topic/87708-clutch-pedal-adjustment/

The clutch disengaged fully with this pushrod when the clutch was slipping but soon as I cut it down to spec at 100mm and tried it before and after changing the clutch - no disengagement. 

BTW I can push the slave piston back by just pushing on the pushrod, is that right? 

Edited July 20, 2022 by Fast28

[Chillidoggy]

1 hour ago, Fast28 said:

Ooh, found out @Cushingwho had the same pushrod as me..

https://www.thelotusforums.com/forums/topic/87708-clutch-pedal-adjustment/

The clutch disengaged fully with this pushrod when the clutch was slipping but soon as I cut it down to spec at 100mm and tried it before and after changing the clutch - no disengagement. 

BTW I can push the slave piston back by just pushing on the pushrod, is that right? 

Yes, that’s exactly what the release fork does, but make sure there’s enough space for the fluid in the master cylinder first, or there’ll be a spillage!

[Fast28]

Success! 😁

After getting my head around the facts of how the clutch hydraulics operate I came to one conclusion as to why my new clutch setup was not disengaging and that was to bleed the slave cylinder again. I placed a ruler next to the clutch fork and recorded the movement on my phone while I operated the clutch pedal. The video confirmed my suspicions that I was not getting the full 18.5 to 19.5mm of slave travel. I think as I was now using the correct 100mm length push rod the slave piston was now required travel further (see explanation below) and the system needed more fluid between the master (noted correct Girling G70 unit fitted) and slave to provide that movement.

I think my original setup had an extra long push rod that must have bottomed out the piston inside the slave cylinder and was preloading the fork hence a friction plate that never fully engaged on the flywheel and was constantly slipping to some degree creating the extra wear and short life of the last clutch. With no preload on the clutch fork using the proper 100mm push rod, the slave piston had to move further than before to provide anything near the previous amount of disengagement. As to why an extra long pushrod was used? maybe the mechanic just couldn't bleed all the air out and resorted to other means to get a customers car appear to work?

So I got out the trusty vacuum bleeder - the best tool ever for bleeding the slave, simple, easy, does the job in minutes and no need to remove the slave. I tried pressure bleeding the system once before but the fluid just leaked out under the master cylinder cap and made a mess. After a few beakers of fluid were pulled through, the clutch pedal was firm throughout it's entire travel. Started the engine and success! I could select all forward gears, if a little notchy. Reverse I had to be gentle with and nurse into position. I made a few small adjustments to the gear selector and translator rod ends as I had changed them for new ones as part of the overhaul and all was good again, reverse still a bit of an issue. Took the car for a 10 mile test drive, filled up with fuel and drove back, clutch worked, didn't miss a gear, biting point now closer to the floor requiring me to relearn getting the car moving off in first but soon got used to it. Car still has the original red clutch hose so something I might look into upgrading soon, never was a problem before but might help to maintain good disengagement to get into reverse more easily after the car has warmed up 🤔.