Update: We have finally succeeded in changing out the CMC. We bled the clutch slave with a pressure bleeder. It made no difference at all, we cannot shift into gear with the car on. The brake fluid reservoir level wasn't dropping when we bled the clutch though clutch fluid was coming out the slave cyl.

 

Maybe someone can explain to me why the brake fluid reservoir level did not drop at all when bleeding but half a bottle of fluid came out slave cylinder?! We used a pressure bleeder that we screwed on to the fluid reservoir with a pressure of 1.5 bar. The clutch pedal was not on the floor during the process. Could it be that air got stuck and wouldn't let fluid move from the reservoir to the master?

 

I went through a similar rigmarole with my son's Fiesta a few weeks ago, it wouldn't go in to gear with the engine running but would start with it in gear and release albeit very close to the floor. Unable to see what was going on in the bellhousing as it has the slave cylinder concentric with the release bearing, I took a chance changing the master cylinder which was much the cheapest option. No change, grr.
As I'm nearly 73 and not as keen on doing this kind of work myself anymore, I asked a mobile clutch fitter to do the work. The problem turned out to be the
Tangential leaf spring deformed as shown in this download: Workshop tip: Clutch Doesn’t Disengage

 

I went through a similar rigmarole with my son's Fiesta a few weeks ago, it wouldn't go in to gear with the engine running but would start with it in gear and release albeit very close to the floor. Unable to see what was going on in the bellhousing as it has the slave cylinder concentric with the release bearing, I took a chance changing the master cylinder which was much the cheapest option. No change, grr.
As I'm nearly 73 and not as keen on doing this kind of work myself anymore, I asked a mobile clutch fitter to do the work. The problem turned out to be the
Tangential leaf spring deformed as shown in this download: Workshop tip: Clutch Doesn’t Disengage

I appreciate your answer! We too thought about it being an issue with the pressure plate but we replaced it a week before the issues started so i can't imagine it being faulty already? We definitely have enough of this and might let a trusted mechanic do the work for us which would cost about as much as the car itself lol. I must mention the car ran already about 292.000 kms with i think original clutch slave and master which we're just replaced...

 

We'll definitely take a look at the pressure plate to confirm our suspicions.

 

Maybe it does not use the brake reservoir. Could it possibly have its own reservoir? Have you bled the brakes?

 

Nope they share the reservoir, we've bled the clutch before and the reservoir level was dropping just this time it didn't. And yeah we bled the brakes after changing clutch etc a month ago

 

Maybe someone can explain to me why the brake fluid reservoir level did not drop at all when bleeding but half a bottle of fluid came out slave cylinder?! We used a pressure bleeder that we screwed on to the fluid reservoir with a pressure of 1.5 bar. The clutch pedal was not on the floor during the process. Could it be that air got stuck and wouldn't let fluid move from the reservoir to the master?

A pressure bleeder usually works on the fluid in the MC so unless you bleed the slave as usual by depressing the clutch pedal fluid can't get to the slave. Sounds like you just drained the slave and it's line of fluid.

 

Ok that would explain it all, i should take another shot at bleeding manually and see if it gets better.

 

This is what MB says: At clutch slave cylinder, open bleed valve (3) until new brake fluid is discharged free of bubbles.This procedure can be supported by sharply depressing and then releasing the clutch pedal every 2 to 3 seconds. Close bleed valve (3)

 

Thank you, i'll make sure to try that one out. We're taking the car to the shop soon to check the pressure plate but before we do that they'll bleed it incase it was a hydraulic issue afterall.

 

What would be the chances of the slave failing? Are the symptoms pointing at it?

 

Could be. As yours is pre-facelift with the external traditional type slave cyl., you should be able to measure it's stroke to make sure it's ok.

 

Have you bled the slave? Can you see if the slave is depressing the fork onto the pressure plate?

What would be the chances of the slave failing? Are the symptoms pointing at it?

Are you getting fork movement when you push in the clutch pedal? If so, how much movement. I've only had to replace a clutch once and that was in '75 when the pressure plate spring failed.

 

I can't lift the car now to check because we returned the hydraulic jack to our mechanic friend after the failed bleeding attempt. Do you think I can somehow stick a borescope into the inspection hole in the bell housing without lifting the car? Honestly I don't think the fork is moving at all because before "bleeding" we could clearly hear the fork barely pushing against the pressure plate, now the noise is gone...

 

You're going to need to purchase a hydraulic jack of your own. If you think you bled the hydraulic clutch system correctly, then you should remove the slave cylinder and push the rod of the slave all the way in, then have a helper push the clutch pedal while you put inward pressure on the rod. If the rod extends then most likely the problem is with the release arm or the release bearing.
Also, do you have the spacer between the slave cylinder and the transmission?

 

Yes the spacer is still there, one thing i noticed is that when we had the trans out and disconnected the slave from the system, the pushrod could be pushed in very easily.

 

Update: We have finally succeeded in changing out the CMC. We bled the clutch slave with a pressure bleeder. It made no difference at all, we cannot shift into gear with the car on. The brake fluid reservoir level wasn't dropping when we bled the clutch though clutch fluid was coming out the slave cyl.

Went back and re-read the posts. You replaced the CMC but not the slave cylinder...I would have replaced both. Sounds like a bad slave cylinder, that would be an easy fix.

 

Went back and re-read the posts. You replaced the CMC but not the slave cylinder...I would have replaced both. Sounds like a bad slave cylinder, that would be an easy fix.

Yeah you're right, it's also cheaper than dropping the transmission. I'll update in 2 weeks after going to the mechanic and changing the slave.

 

Update: It really is a one of a kind case. Mechanic dropped the trans and found the pressure plate and clutch disk in good shape, says he doesn't see any abnormal damage that could indicate a problem with the clutch. He also checked the slave cylinder and said it worked perfectly. Here are the pictures i could make and maybe one of you can spot something out of the ordinary:

 

Next step would be to install a brand new PP and maybe we might as well put in a used transmisson with 150.000kms since there is a little play in the shaft and we probably damaged some synchros trying to put it in gear we a non-working clutch operating system...

 

Check it as sillysod suggested or else send the entire clutch off to a clutch specialist who will be able to check it for pressure plate alignment and how it releases. Does not have to be a Merc specialist, a clutch is a clutch.

 

I would compare the tangential springs on your cover with another new item to make sure they are not deformed. They should be pulling the pressure plate towards the cover. Compare how flat item 6 on this is to yours. https://1.bp.blogspot.com/-zwFXywUw.../UQDoRRkntyI/AAAAAAAABGc/q0E_B9I_w3Q/s1600/Standard+diaphragm+spring+clutch.jpg and item 4 on the diagram here US4640398A - Friction clutch with tangential leaf springs - Google Patents

 

Honestly, it's hard to tell because i've seen pictures of other pressure plates and the leaf springs are all a little bent just like the ones on mine. If you check picture 7, you'll see that there is a little gap between the leaf spring "pinhead" and the ridge it's attached to, it looks like this isn't normal. It's fine i'll replace the PP (we learn from mistakes and i shouldn't have driven so aggressively with a new clutch anyway). In addition, maybe someone has experience with this, there is some bit of play in the input shaft of the transmission. Should i worry about this?

 

Thinking about it some more, the diaphragm spring is trying to move the pressure plate in the direction of the flywheel and the leaf spring is trying to move it in the other direction. This view seems to show a slight curve on the spring as it tries to counteract the force of the diaphragm spring. Clutch Pressure Plate View Clutch Disc Stock Photo 2377577389 | Shutterstock I see what you mean about the apparent gap between the rivet head and the casting - is there any play here because that would remove some of the spring action. I would be inclined to return the clutch to the manufacturers for their inspection/opinion/replacement.

 

There is no warranty on the the site i bought it from so i wouldn't bother trying to contact them at all. It was a LuK PP so this time i think i'll get a SACHS one maybe it is better quality... And no i did not notice any play at all whatsoever on the pressure plate.

 

Ok the SLK now shifts well again and everything works as it should. What we ended up changing out; clutch assembly, clutch slave, clutch master, clutch line and transmission. Hopefully the car won't ever leave me stranded again! Thank you everyone for keeping me sane while i go through the pain of having a car broken down for months after purchase! Still need new all season tires and control arms though :/

 

Did you closely compare the tangential springs of the two clutches?

 

we will mark as resolved