Rear Main Seal

[Harry]

1966 230SL.  I will be installing the pan soon and I am looking for instructions and advice on how to do this right.  It would be excellent if the end result did NOT leak oil!

Thoughts?
Harry

[ja17]

Are you replacing both halves or just the part in the oil pan?

[Harry]

Both halves, Joe.

[Benz Dr.]

This would mean that you have the crank removed. There's a way to do this job if everything is all apart and a different way if you only have the oil pan off. BBB will not get you there with just the pan removed.

[Harry]

I just had the engine bored and 1st oversized pistons put in, so the crank is in.  So if it is best to remove the crank, I can do that.

[Benz Dr.]

It depends on how you cut the seal that's still in the block. If you cut it level with the parting surface get your wrenches out and pull the crank out. Seal should be cut .50 mm or .020'' above the block on each end and oil pan should be done the same way. I made a tool, .020" thick, that fits around the seal and I cut it off with a razor knife.

[ja17]

Clean the groove in the block and the oil pan first. Notice that there is a pin in the groove of each. Early BBBs show using a hammer handle to work the seal down into the groove. Mercedes offered a special tool in later days. It has the same radius of the crankshaft and is used to install the seal. Don't expect perfect results. Notice that the crankshaft is machine knurled where the seal touches the crankshaft. The reverse, parallel knurling "\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\"  helps sling the engine oil back into the oil pan as the crankshaft turns. With a used engine the knurling may be worn smooth and be less effective. If you have a late BBB you can go to 03-4/1 through 4/7 for the seal installation procedure. I noticed these days that the rear seal is made from improved material over the originals (probably Kevlar) and is very tough and hard to cut. The manufacturer spec for overlap is slightly different than in the BBB because of the new material. Probably not that critical as long as you do not cut it too short.

[Harry]

Thanks very much.  I do have a BBB that I will consult.  Often with jobs like this, there are nuances people might use from experience of having done many times.  Just didn’t want to miss any of those.

Thanks very much!
Harry