Flywheel, clutch and mounting engine stand

[waqas]

Hello all,

I finally got around to removing my 230sl's engine and transmission for some maintenance. This is the first time I've been in this area of the car, so I've got a list of basic questions to ask. I've uploaded a bunch of pictures, so please point out if you see anything funny (i.e. not quite right).

Here is a picture showing the clutch pressure plate after transmission removal. Notice the slight wear on the three levers on the pressure plate.
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Here is a picture of the clutch plate after the pressure plate was removed. I don't know how to tell if the clutch plate is worn out, but I think I'll replace it anyhow.
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Here is a picture of the pressure plate driving surface. How do I tell whether the pressure plate needs to be replaced?  Can the driving surface be re-machined if it's warped?
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The back of the clutch plate looked very rusty... or at least like there was a lot of moisture trapped there. FYI-- car has been sitting for a couple years. More confirmation that it needs to be replaced. Any cause for concern here?
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In fact, even the flywheel has some rusty-looking surfaces, as shown in this picture.
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Is there a way to measure any possible warpage without removal?  
Do I need to have a machine shop smooth the surface for me?
Or can I use some technique without removing the flywheel?
If I need to remove the flywheel, do I remove it from the six bolts in the middle shown there?
This is a 127-II engine, so do I need to make any marks before removing the flywheel?

Next, I'll be mounting the engine onto an engine stand.  Do I need to place anything between the yolk arms and the bell-housing flange to avoid damage to the flange edges?  (washers, etc)   Or am I being overly paranoid?
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When attaching the engine stand yolk, can I safely use the bolt pattern shown here:
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My instinct tells me it's probably a good idea to put some grease on the yolk before placing it into the engine stand mounting hole, so I can turn it easily. Is this a bad idea for any reason? (if not, will any kind of grease do?)
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Lastly, is this stand adequate for our engines? (Harbor Freight)
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Thanks for any answers you can provide!

[glennard]

I've the same engine stand and the same questions.

[ja17]

Hello Waqas,

It looks like your making progress! Normally the clutch disc is replaced with the pressure plate, and throwout bearing if either item is marginal. A quick visual can be done by looking to see how much lining is above the rivets. Once the lining is worn down to the rivets the clutch will begin to slip.  Most likely the BBB has a minimal lining thickness also.

Slight wear on the fingers of the pressure plate is not unusual. Significant wear would most likely be caused by the throw out bearing.

The springs in the pressure plate can get weak over the years, however it will usually last the life of the clutch disc. Any of these surfaces can be remachined. It is common proctice to machine the flywheel if it has any uneveness to it. I had a competition pressure plate made for my rally car years ago. They added a inner springs to all the springs (double sprung) just like the engine valves!

The pilot bearing is in the end of the crankshaft and holds the input shaft of the transmission. You should check it and repack it with grease. It is a puzzle to get out.

If nothing needs machined, a light bead blasting will knock the glaze of the flywheel surface and pressure plate giving the used assembly new clutch "bite" again. (The pilot bearing must be kept clean).

You will have to decide if you are using the old assembly or replacing everything.

A slight film of grease on the fingers of the pressure plate and on the surface of the throwout bearing helps reduce wear (not too much).   The inside mounting sleeve of the throwout bearing has a groove for grease. Be sure to remove the sleave (throw out bearing can stay put)  and refresh the grease.

A special clutch alignment tool, or a old trans output shaft is used to align the disc with the pressure plate when re-assembling the clutch assembly. Most autopart stores will sell an inexpensive plastic clutch alignment tool.

Your HF engine stand should be fine. Save your cash for the expensive Mercedes parts!

Carry on!

[waqas]

Joe, thanks for your reply! I'm always very grateful for all the detailed info you provide.

I shall follow your suggestion and replace the throwout bearing, clutch and pressure plates together, if necessary.

I have 2 more questions:

• As you well know, this is a 230sl and as such the flywheel is balanced to the crankshaft (and harmonic balancer/damper).  Do I need to make any alignment marks before I remove the flywheel?   Or is there some kind of unique alignment dowel/pin/etc mechanism that precludes incorrect re-installation?
• In order to disconnect the flywheel, can I simply remove the six bolts in the center?

Thanks again for all your help!

[waqas]

Ok, it looks like Section 03-3 "Removal and Installation of Flywheel" of the later BBB (1968-1972) answered my questions (no, yes, yes). The earlier BBB (1959-1967) does not have a Section 03-3, which is what had me perplexed (has all the updates). I hardly ever look at the later BBB, but it appears I should keep them side-by-side.

Another 230sl-specific question:  If the flywheel needs to be re-surfaced, does it then need to be re-balanced with the crankshaft?

[ja17]

Hello Waqas,

You will notice that the flywheel is already pinned and can install one way only.

You will not need to re-balance after re-surfacing. The amount of material removed is minimal and evenly removed.

[Benz Dr.]

Flywheels should be ground not machined, ever! The machine that is used to grind a flywheel has a table where the flywheel mounts. As the table slowly turns a cone shaped frinding wheel is set to just contact the flywheel surface. The whole surface is ground in one pass which makes it level and smooth.
Machining the flywheel on a lathe is a big mistake. Hard spots in the metal will cause the cutter to chatter over those areas and a lot more material would need to be removed to get down to softer material so that you end up with a nice surface. The grinder will cut right through those hard spots ( and there will be lots of them ) without any trouble.

You can ruin a flywheel using any other method other than grinding. Since this is a stepped flywheel you will have to remove the same amount on the upper surface where the clutch cover is attached. If you take a .005'' cut on the clutch plate surface you need to take the same .005'' cut on the presure plate surface. Pay strict attention to machining tolerances such as the maximum alowable wear limit and particularly the base amount between the upper and lower machined surfaces which must always stay the same. Any failure to stay within these limits will give you a great big door stopper.

[waqas]

Thanks for all the great advice, Dan!

Once I remove the flywheel, I'll take it to a machine shop to tell me if it's straight or not. Given all these issues, I'd rather not risk having to get a new flywheel and all the associated headaches (rebalancing to crankshaft, etc, etc).

I'll report back with results.

[waqas]

So I removed the flywheel:
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Notice there's a lot of oil accumulated near one end of the flywheel (that last shot shows it clearly). This was the lowest end of the flywheel when it came out. I'm guessing the rear main seal needs to be replaced.

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Also, there seems to be some slight damage to the ring gear teeth:
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Is this anything to be concerned with?