return spring, 230sl clutch pedal

[enochbell]

The clutch pedal on my '64 does not always like to return all the way: clutch is fine and the feel is good once the pedal gets down to the point of actuating the clutch but the first inch or two of travel is almost without resistance, causing it to hang and requiring a light tap on the pedal to get it to come all the way back up.  Can I assume it is a weak spring in the pedal assembly?  I have a new spring, can it be replaced with the pedal assembly in the car or is major surgery in order?

Thanks for the advice,

Greg

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

[ja17]

Hello Greg,
It is not usually a problem with the spring in the car.  First check to make sure your clutch fluid level is up.  Next The slave cylinder on the transmission must be adjusted correctly also. You should have just a bit of freeplay at the fork and the linkage rod.

The clutch hydraulic hose must be unristricted. They swell closed like brake hoses. Replacing these will usually make an incredible difference. The pedal and clutdh will respond much more quickly.

Lastly there is a procedure for adjusting the spring in the car. This is usually not the problem.

Joe Alexander
Blacklick, Ohio

[enochbell]

Joe, thanks, I hear you regarding the liklihood that the problem is everything but the spring.  But would you please think on this and give me your opinion:  the problem is only in the first 1-2 inches of travel (freeplay at the pedal)-- once the pedal gets to the end of freeplay the action seems fine.  It hangs up at the point that the action is fully released/clutch fully engaged but before the pedal has recovered from the freeplay.  Finally, there is a very tired creaking/groaning coming from the pedal action, I have oiled as best I can but to no avail.

Your thoughts are appreciated.

Thanks,
g

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

[ja17]

Hello Greg,
I would check the freeplay at the slave cylinder on the transmission first. The return of the pedal at the top is very influenced by the amount of freeplay at the slave cylinder. Adjust the freeplay to almost gone bu t leave a bit. You may want to remove the slave cylinder return spring for the adjustment so you can easily feel the amount of freeplay.

The spring inside the car is a push/pull kind of action it cams to pushing the pedal upward at the very end. It changes over to pushing the pedal down shorlty after. Hydraulic pressure generated by the clutch plate helps return the pedal to the top changeover position then up to the top.

You may have an inside spring adjustment problem, but before you get it all  adjusted out of wack, make sure the clutch slave cylinder is adjusted to the correct clearance. If your clutch pedal does not return quickl;y from the bottom you may have a restricted hydraulic hose.

Groaning noise from the springs is not that unusual.

Joe Alexander
Blacklick, Ohio

[A Dalton]

JA has it pretty well  covered .
 I would like to add a couple of other odd points that I have run into on these systems.
 If the free play adjustment is in order,  a small amount of air will cause the same condition , so I would do a quick bleeding of the system..
On the hose issue.... if aged , just change it.  These suffer the same interior restrictions the brake hoses do , but they don't seem to get changed..  [ just overlooked, I guess]
I do this change just as a peventive maint. measure. Short $$$$.
 On the groan noise issue ...The master has a dirt/dust cap bellows on top and they crack/rot, allowing dirt into the master.. I have seen these make noises as the piston is at the top of the stroke.
You can usually isolate/pin-point this w/steth on the side of the master as you pump the pedal or simply squirt some WD40 there . If  the noise ceases , you have prob found this to be the problem.
 One last place I do look at while making your adjustment at the slave is to check the tightness of the two bolts that mount it.
 The early .042 used hex bolts threaded into the mount . On later units this was change to studs w/nuts to rectify a thread stripping problem they had with the earlier mounting.  Just something to check while doing any type work/adjustment on the slave unit.
Good Luck.
 

[enochbell]

Thanks JA and Arthur, that is really helpful.  I already had the dash apart to repair a broken heater flap and to glue the cap back on the tach needle.  Otherwise I probably would not have attempted this clutch pedal work, after all the clutch actually works fine.

Now that I am in, and with the help of your posts, what a surprise!

The creaking was coming from the rod that goes through and retains the pedal spring.  A little grease and the creak is gone, but the rod has a wear notch in it (right where it emerges from the spring plate, closest to the driver).  I left that for another day.

The return problem was cured by bleeding, THANKS!  And I will order a new hose to replace the old one, which looks pretty tired.

In the meantime, I did remove the concentric adjusting bolt that holds the master cylinder plunger to the pedal arm.  Did not know it was concentric until after I removed it.  I just put it back in the "middle" adjustment position, hope I did no harm, but I can not find any spec. that would tell me how to properly adjust this. The adjustment seems to manage the amount of freeplay before the master clutch cylinder is engaged.  It works, so I guess I did not screw it up, but if anyone knows a spec, I would sure like to put it right.

Also found that the spring compression was not to BBB spec., it was 3 mm too wide, even though it had the original paint mark on the nuts.  Now it is "right", but hard to believe it was assembled wrong at the factory?

Thank you guys, this is one cool piece of engineering and a lot more complicated that I imagined.

Greg

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

[A Dalton]

On 113 , the notch is at max eccentricity when facing rear of chassis
 The spec is .2-.5mm at the piston , but you have to use feel for the adjustment, as you can not measure in there.
 Just as long as there is a little play , you are OK.

[Ben]

I've had this problem too, for a long time !

This weekend I removed and replaced the seales in the master cylinder. I replaced the metal pipes and the rubber flex pipe too, then bled it from the caliper. I also did Naj's trick of moving the slave lever back and forth !

This last method is very effective and I could actually hear the air being prged from the system. I ended up with a perfect pedal !

I reckon I will do the seals in the slave soon too since its easy to remove etc.. !

One thing though, I had an old slave that I opened but I dont recall what the piston/seal arrangement is !

Does anyone have a photo of the internals ??

Regards,
Ben in Ireland.
'64 230SL 4sp.