Confused by clutch return spring

[twistedtree]

I'm working on the clutch on my '70 280SL and am confused by the return spring, and whether there should even be one. To be clear, I'm talking about a spring under the car running between the fork and slave cylinder, not the spring that's part of the peddle assembly inside the car.

There was no spring on the car when I got it and the clutch was dry of fluid, so I've replaced the master and slave cylinders and fabricated a new line from the reservoir to the master cylinder (the old one rotted and broke off), and am ready to bleed the system, but I'm not clear on whether there should be a return spring from the fork to the slave cylinder.  There is a hole on the end of the fork where a spring can attach, but no hole on the slave cylinder.  From the parts books I've seen it looks like only the older style slave cylinder has a hole for a spring.

My best guess at this point is that the newer cars do not have a return spring down there.  Can anyone clarify?

Thanks,

Peter

[w113dude]

Peter,
You are correct, they don't have a spring. The hydraulics do all the work.

[pagoden]

Peter, Shaun -

Yes, and when I ran into this on my '69 280sl, the explanation (from K & K, after some conferencing) was that sedans got the slave cylinder with the hole in it for the other end of the spring and our 113s got the cylinder without even the 'ear' cast onto it -- which would have the hole through it for the spring -- and so it followed that the 113s properly operate without benefit of a return spring.  I wasn't entirely comfortable with this setup but did find a few photos in various manuals to support it so went ahead.  A couple of years later and not really so many thousands of miles -- but really, rather many shifts -- later, all seems to work well without the spring seen in some under-chassis photos.  And I still don't understand it.     Anyone?

Cheers,

Denny


[dang, missed my chance to feed you all some 1 April nonsense!   Happy Spring all.]

[tel76]

Have a look at Thelews underside in the Jack Stands post, this shows the spring position.
If you do not have a spring fitted there is a very good chance that your clutch release bearing could be constantly in contact with the pressure plate.
Not a good idea.

[twistedtree]

Have a look at Thelews underside in the Jack Stands post, this shows the spring position.
If you do not have a spring fitted there is a very good chance that your clutch release bearing could be constantly in contact with the pressure plate.
Not a good idea.

That's the source of confusion.  As best I can tell, 230s and 250s have the spring, but 280s don't.

[mbzse]

As best I can tell, 230s and 250s have the spring, but 280s don't.

Correct. This is due to the fact that manual M130 engines were fitted with a so called
diaphragm (also named membrane) clutch. No need for the return spring on the lever on these.

Earlier M127 and M129 engines had nine coil springs for the pressure plate instead.
/hans in sweden

[pagoden]

Why wouldn't the diaphragm type need a return spring to remove the throwout bearing from constant contact with the clutch assembly just as much as the previous ones did? 

I thought the diaphragm type was a solid improvement over coil spring pressure plates when they came out but don't see how they get away from the need to ensure that the t/o bearing isn't being spun by contact with the clutch assembly between shifts.  [The cars I was familiar with in those days didn't discontinue the use of return springs when they went to the diaphragms, so I've never had to worry my tiny mind over it before.]

I don't think that mine really is spinning all during the time the engine's running -- but why not?