How long can I ignore a leaky rear main seal?
 

Yep. It's leaking alright. '79 450SL. Can I ignore it for now, and keep an eye on the oil level...or is there the possibility of catastrophic failure?

I have some quotes -- it's not the worst job on earth -- but I won't tackle it because I don't have a lift (and I don't like pulling trannies anyway)...

Are you shure its the rear main seal. I pulled the tranny on my 560SL only to find it was the head gasket.

John Roncallo

I have the same fear aswell.


Leak looks to be coming from the end of the block, right where it meats the tranny. What are the symptoms of head gasket problems? - It's also been running quite bad.

Aw man....don't scare me any more than I am already!!! :D

As far as I know the oil leaks in the 117 alloy engines head gaskets are limited to just leaking oil. Your 450 is not an alloy engine, it is an iron engine. I'm not sure if these tend to progress into the water jackets or cylinder. Therefore I belive you can drive forever with either an oil leak from the head or rear main seal, providing you dont run low on oil.

On my 560SL the oil would leak out of the head and fill the valley between the two cylinder banks. It would then over flow out of the back and dribble through the crank shaft sensor port and come down at the bottom of the bell housing just like a rear main seal leak would apear. You can search on some of my earlier post of about February March 2005.

As far a a 300 six I have no experiance with a leaking head gasket.

John Roncallo

I've been ignoring a leaking rear main seal and watching the oil level on mine for about 18 years. :)

Len
'83 240D 345,000 miles original owner

Okay...now you guys are starting to make me feel better! :D

It's not the leak you should worry about it's the dipstick level!

Recent response to tech question in The Star notes that most pre-1984 Merc engines require crankshaft removal to fix leaking rear main seal, so it's clearly something to avoid as long as possible.

I think the M117 V8 engine is an exception to this rule. The Haynes manual and the price quotes I received bear this out.

However, if someone wants to correct me on this...I'd rather hear it now than later!

I was quoted $800 parts & labor for me pre-84 V8 rear main seal.

I got 2 quotes: One for about $700-800, and another for $575 labor + $100 parts. So we're in the right price range here -- and I can't imagine pulling the crankshaft at that price...

page62,

I doin't know if you repaired the rear main seal but if it is not broken there is a product that will clean it and stop the leak I have used this product on two engines with rear main seal leaks and it stopped the leaks that was a year ago and no leaks today it is Auto-Rx.

Daryl

where do you buy the auto-rx? i have a 1990 560sel with that leak

i think the main point not directly mentioned yet but nearly touched on is the fact that a rear main seal will not normally every have a massive failure which would endangeer the engine.

they just keep leaking.... and sometimes dont really get much worse with the years.

tom w

Nearly forever. Eventualy it will be leaving a stream of oil, so you will eventualy have to fix it. But if it's only leaking a bit you can ignore it for years and years.