Naughty clutch

[georgem]

We own a 230 sl.

When we bought the car,about 3 years ago, the clutch pedal on occasions used to stick about half way up and go soft. After some bleeding and oiling the pedal mecanism, it worked - most of the time until I got fed up with it and replaced both the slave and master cylinder and reverse bled it. Problem solved.

The other day, after an an unusually long and extended period of traffic/city stop start driving, the clutch went soft again, pedal engage/disengage point near the floor, with the pedal sticking half way up at the point where the over centre spring works. I had to flip my toe underneath it the get it all the way up. Once I moved it past the half way point, it flipped up by itself. After sitting in the garage over night and reflecting on its naughtiness, it had a change of heart and worked fine the next day, firm pedal, engage/disengage point about half way up, crisp engagement, no shudder or slipping. By the way, it had not lost any fluid.

So, in summary, I have an intermittent clutch problem, occassionally, the pedal becomes soft with the point of engagement moving to close to the floor and the pedal stopping at the over centre point when being engaged. No fluid loss

Are there any suggestions please

PS The Mercedes Benze Club is active in Brisbane - a couple of weeks ago we had our annual concours at a historic mansion -about 50 cars of all ages and about half a dozen SLs. Great day. Bob have u any photos  that you could post - all my photos were of SL interiors and engine compartments - a bloke should get out more...............

George
Brisbane
230SL
Austin Healey 3000

[enochbell]

George,

I had the same symptoms and went to great lengths to correct, going so far as replacing the return spring (what a pain) when it turns out that the fix was simple, as suggested on this board.  The answer: the adjustment of the freeplay at the slave is critical to getting the pedal to return properly, get the specs and make this adjustment and I bet $.05 that it will correct.

Best,
g

'64 230sl, fully sorted out...ooops, spoke too soon

[Naj ✝︎]

quote:The other day, after an an unusually long and extended period of traffic/city stop start driving, the clutch went soft again, pedal engage/disengage point near the floor, with the pedal sticking half way up at the point where the over centre spring works

How old is the hydraulic fluid in the system. Seems to me it may be boiling under heavy use... :twisted:

naj

68 280SL

[hands_aus]

Hey George and Naj,

George
I loaded some pictures on the 'PHOTOS' section. I have a cd with 200 pics on it.
Do you have the Service Manual for your car?

I don't have a manual car so here goes... does the pedal have pivot points that need greasing? Is the carpet in the way?

As Greg says he had to replace a return spring, is it possible that the one on your car has weakened?

Naj,
Does the clutch fluid need to be replaced regularly like the Brake system?

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[Naj ✝︎]

quote:Naj,
Does the clutch fluid need to be replaced regularly like the Brake system?

I would say 'YES'.

My partner surprised me with a brake fluid tester a few weeks ago with red/amber/green leds. Tried it on the clutch fluid when I got home and it showed up red.

naj


68 280SL

[al_lieffring]

The clutch pedal on a Mercedes has a return spring that has the unique feature of an over center spring design that allows the spring to assist the driver in holding the pedal down.

at the top of the pedal stroke the spring is pushing the pedal up, at the bottom it is pushing the pedal down.

If the slave clyinder is not adjusted correctly, or if the hydraulic system is not working properly, the spring tension of the pressure plate will not ruturn the pedal past the over center point and the pedal will stick half way down and need to be pulled the rest of the way up with the tip of your toe. So replacing the return spring will not help in this situation, it is working as designed, the hydraulics are where the problem lies.

These cars often sit parked for long periods of time now and the valves in the master cylinder can stick, causing the clutch pressure to bleed off at long traffic lights. Useing the clutch could eventually free this up, and keeping clean fluid in the system sure couldn't hurt anything. I doubt that the temperatures the  clutch system is exposed to could ever cause boiling though.



Al Lieffring
66 230Sl
Jones'n for a new gas tank

[Naj ✝︎]

quote:I doubt that the temperatures the clutch system is exposed to could ever cause boiling though.



Al Lieffring

 :oops:  :oops:  :oops:  :oops:  :oops:  :oops:  :oops:

naj

68 280SL

[georgem]

Guys,

Thanks for the responses so far and I shall try them, esp checking the adjustment at the slave and changing the fluid. One thought I did have was re the flexible hose in the hydraulic system. If the wall has perished/weakened and everytime the clutch is pressed the pipe expands like a balloon, could this give the symptoms? (I assume there is a flex hose in the system - I haven`t checked yet!)

Bob, I shall check the photos - and yes thanks I have the CD.

Cheers


George
Brisbane
230 SL manual (with a bloody minded clutch)

[Raymond]

There is a short flex hose between the slave cylinder and the tube to the master.  I'd imagine it would have to be swelling like a bratwurst to cause your symptom and it wouldn't last long like that. It would be readily apparent if you get under and look.  Might be worth changin just for age and preventive reasons.

You said you replaced the master and slave three years ago and have not had the problem since.  You might try flushing the fluid and, as others suggested, check the free play.

Ray
'68 280SL 4-spd Coupe

[114015]

George,
Raymond is correct.

Check the flex hose although you won't see anything from outside. Most likely it needs to be replaced when old. These hoses ages in the same way as the brake flex hoses; after 20 or so years those are completely glued inside due to deterioration caused by the brake fluid.

Unscrew it on the slave cylinder side and press the pedal; most likely only little or no fluid passes through, at least not enough in the reverse direction to release the cylinders and pedal.

Replacement should be considered even if the hose appears to be alright.

Good luck!


Achim
(Magdeburg, Germany)