oil leaking question

[xcashewx]

my 230sl had a engine rebuild about 50k back, but it was stored for a number of years, upon "reviving" it there has always been a leak from the rear main seal, it used to be really bad but i put in some lucas stop oil leak just as a "band-aid" and it slowed down quite a bit, but this was temporary since the only other option is removing the trans to replace the seal..etc  however i notcied today that on the crankcase vent line that runs to the throttle body has a slight almost kink in it, air can go through it but doesnt seem sufficent, and some oil drips out of the rubber hose from v/c to the pipe, could this kink be making the pressure in my crankcase higher than normal? causing little bits of oil to be forced through the seal? i have noticed i always have a high oil pressure ,it usually never will go below 45
is there an option i have to test  before resorting to a seal repair? i was thinking maybe just disconnecting the line alltogether and seeing what happens..
i just wanted to hear some others opinions on this  thank you!

[Dash808]

Personally I doubt that enough pressure could be built up to squeeze oil out your rear main.  Especially if just the vent has the slightest bit of opening. 
Shouldn't be anything wrong with disconnecting the line to see.  Mine runs out of the valve cover and vents down underneath the car, and the connection on the throttle body is blocked off.   Very emissions friendly car I have 
I'm sure someone who knows more will chime in. 

[Allenh]

First, the crankshaft seal seals against an area that is dependant on primary oil presuure generated by the oil pump and the condition on the load bearing surfaces of the engine bearings,etc.  Internal crankCASE pressure is totally different and not related to oil pressure. 

All of these engines in decent shape will always hold the oip pressure gauge against the upper stop. You know you pressure isn't low, but is the oil relief valve working?  It is possible it has malfunctioned, but I doubt it.  Unfortunately, the most likely causr is a poor job of installing the seal. 

I found an interesting instruction in an OLD service book on M/B engine assembly, one is instructed to soak the new seal with tallow before installing.  I did this and also made absolutely certain the seal was fully seated around the crankshaft recesses before I trimmed it and came up short on length.  I'll bet you seal is trimmed too short and that is why it is leaking.   These 2 part seals are tough to do well.  I have done many and only my last three have been satisfactory to me.

I am not sure of your stlye of crankcase ventilation at the throttle body, but I bought a funky rubber elbow in the Help section of my local Auto Zone.  One end was perfect and the other end I shortened, and enlarged the hole for the vent tube and it works perfectly and looks as if it was original, the fit is perfect!  No kinks. 

Ihave a picture but can't seem to post it into this reply.

Allen     

[xcashewx]

thanks for the advice!, so i guess my only option is to replace it the seal then, is this an engine out job? i read the whole engine pretty much has to be taken apart

[al_lieffring]

Replacing the rear main seal correctly is a subject for an entire tour thread, too much to fit into a single post.
in partial answer to your question the upper half of the seal can only be replaced with the crank shaft removed from the block.
If there is visible blow-by puffing out of the valve cover vent when the hose is removed, it would indicate piston or ring replacement would be needed, so why take the motor 75% apart and only do half of a rebuild?

[Allenh]

Yes, It is an engine out job.  But, if the engine was well rebuilt 40K ago, If your certain about that, I think that just the repair of this seal and the rest of the bottom end seals would be sufficient. 

These are tough and very durable engines, they are in fact MercedesBenz!  Check the plugs for signs of oil problems, from rings or valve seals.  If there is, you might consider more work.

If you have the means to remove the engine, this is a job you can do yourself, you just fixed your tach, that was a different type of repair for you.  this is more "work"  But it is do-able. 

The member before my reply says there is a whole thread about the seal, it isn't that daunting.  but to do it right, follow good advice to the letter.  I'll help you if you want.  I have done a few.

Allen 

[xcashewx]

the engine it self is fine, no smoke from the vent, good compression ,and spark plugs have no oil, just normal tan-ish stuff, so im guessing the guys who rebuilt my motor obvisouly didnt do the seal right, ill look into the job but can some one give me a link to this thread? id like to see how much disection of my engine is needed

[Benz Dr.]

The oil seal wasn't installed correctly or it wouldn't leak. They all tend to seep over time but won't leak that much if done right.
I made a tool which I use to cut the seal off just above the block surface. I you cut the seal at the surface of the block it will always leak oil. You can remove the pan and remove the rear main seal that's in the pan. Cut the ends about .040"  high to compensate for the seal which has likely sunk into the block a bit. Use a small amount of sealer on each end of the seal and then a light amount all the way aeound the pan just before you install it. This should fix it.

If the seal is lower on one of the block than on the other side you may need to cut one side longer than the other. Use two feeler gages on each side of the seal to maintain the correct cutting height. One side should be about .040'' if the seal is flush with the block height and the other might be more if needed.
Install the pan and try to turn the engine over by hand. If it's locked up the seal is cut too long. Remove the seal and cut it again using a shorter lenght. Repeat until the crank turns freely. Normally, .020'' sticking out on the block and the pan will give a perfect seal without binding. What you are trying to do is reproduce this crush fit that the seal has to have.

[Allenh]

Nice description.  you know, It is most likely that the issue is a short cut seal rope.  Thre trick is always to get it fully depressed into the cavity so there are no surprises.  If the seal isn't too worn. you might be able to replace the seal half in the pan and cut it a bit long. 

A totally new seal would be the best way to do it, but it is possible to do the bottom half in a weekend and drive the rest of the short summer away!

PS, you cannot totallt remove the pan with the engine in the car.  I am pretty crafty and capable of being very careful and intricate.  I think I could do it.  Would you feel up to it?

Allen

[Benz Dr.]

The trick to getting the seal well placed is to use a hammer handle and tap it in with another hammer as you roll the seal into the groove. There's small pin that keeps the seal from spining in the block or pan and you have to force the seal over it and into place.

[xcashewx]

ok an update.
i decided to drive with the vent disconnected and i havent seen a drip yet, although another leak sprouted, right where the oil pressure hose meets the motor, i tightened it a little and it slowed down, is there an o-ring under there? also,when i had the vent disconnected i notcied a little bit of "smoke" i guess you could call it, i took a picture with it running but my camera doesnt show it, its only really visible if you look at the right angle

[SteveK]

I recently had my oil pressure line off.  There is no "o" ring, it's a metal to metal compression connection. 

[Benz Dr.]

If you have no oil leaking out now the engine may have been building up crankcase pressure. The early cars had a metal line going to the throttle body and they often fill up with rust. In very cold driving conditions ( yeah I sometimes drove my car in Dec. ) the line would fill with moisture and freeze up. The pressure in the engine would come out the area where the tach cable screws on and make a real mess everywhere. Check that metal line to see if it's clear.
Some blow by is normal but every engine has to vent to work properly.

The oil pressure line is a compression fitting. If it's leaking in that area it's most likely that the fitting that screws into the filter housing isn't tight. There's an aluminium seal under this fitting which you may need to replace. I believe you would need to remove the filter canister before you remove this fitting that the oil pressure line attaches to.