Oil leak from the rear seal 420 SEL

No good way.

When you had the oil leak did you get a burned oil smell in and outside the car? My car is leaking a very small amount of oil, but what bothers me is the burning oil smell. Unless there is a hole in the exhaust pipe...

Is there any other problem using this type of oil besides dependency?

Nope.

You have to tear into it to replace it. And guess what happens then? It leaks!

Seals rarely fail, compression blowby forces the oil past an otherwise ok seal.

Not exactly what you wanted to hear, huh?

Richard: What is the ultimate fix for a leaky seal?

Larry

If there's nothing else wrong with the engine, replacing the seal will fix it. If there is an over-pressure situation inside the engine itself, then replacing the seal is a waste of time.

However, if the leaking was caused by an over-pressure situation, then the rear main seal shouldn't be the only leak. you should see other leaks at other key junctures...

Look around carefully, if this is the only leak you see, then the odds are you can replace the seal and it will fix it.

Marty

Replacing the rear main seal is $1800-$2200. Not worth it. Richard

As far as that smell, also check that you don't have a gas leak at the lines at the fuel filter. I don't care to recall how long I was driving around with a serious gas leak right near my exhaust. It gave me a raw gas smell inside and out. Richard

Not worth it at that price...

Fix the compression blowby. Usualy it's just the head(s) or rather the valve guides

A leakdown test will tell if if there's compression gasses getting past the rings (reasonably unlikely, but you do need to check it).

Maybe, but I've seen just the rear main leak, maybe it goes first.

Test and measure: do a compreession check.

Just the rear has been leaking on my 380 for 9 years. Richard

No! The tranny must come down, the flywheel has to be removed from the back of the engine, and then the old seal is removed, the "seat" carefully cleaned, and the new seal inserted correctly. Most "shops" insert the seal by lubricating it and taking a large socket and pushing it into place. The Mercedes dealer has a special tool designed for evenly seating the new seal. Which is why they guarantee the job for a year. They usually give a package price since they need to drop the tranny anyway, they replace the front seal on it in addition to replacing the crankshaft seal ("rear main seal"). P.