Hello all, this is my first post.
I bought myself a 2003 SL 600, and first having had to fix that stuck gearbox shifter, and finalizing that with good results, i did observe some oily parts under the car. It seems to be around the insulated pipes going along the length transmission pan.
Can some of you with experience tell me why these pipes are oily, and what part numbers they have, so I know what to order and what to replace?
Having said that, I have been at the local MB dealer, and they had no clue on anything to be honest, and suggested I took the car to them so they could check it out..

 

it appears to be the ABC hose that goes from the pump to the pressure control valve that is located at the rear of the front driver's wheel well (marked #550 in the first diagram). this is a very common issue as the heat generated in the engine compartment really hammers on the hydraulic ABC hoses. Also check the ones that run under the radiator (hoses #60 & #90). Those are also prone to start leaking. I would get this fixed ASAP bc when that hose finally goes (which it will burst eventually) it may cause the ABC pump to ingest air if you don't get the car turned off soon enough and also ruin it (which is a part that costs over a grand). The part numbers for these hoses have been updated several times over the years and if you give your dealer this diagram they can tell you what the current part number is and cost. I can tell you on the V8 models the hose is about $500. This hose on the v8 (part #380) has a dampener built into it and should NOT be rebuilt by a hydraulic hose shop (which is something you can do with the other ABC hoses in the system to save money). I am not sure on the v12 models. It appears on them part #500 acts as the dampener and you should be able to have the hose that is leaking on yours rebuilt. Regardless, I would imagine most of the hoses in your engine compartment are reaching the end of their service life if one is leaking and they should all be replaced as prevent maint. If you want to save money on the part (assuming you need to buy the MB one and aren't having your old ones rebuilt), go to mbdirectparts.com, they are an MB dealer in Omaha that sells parts at wholesale online.




Here is ABC routing for both v8 and v12 from pump to pressure control valve.



Here is routing for front ABC lines.



Here is routing for rear ABC lines.

It also might be your rear main seal leaking oil (there appears to be lots of oil where the tranny meets the motor) on the hose and running down it making it appear that the hose is leaking when in reality it is the engine. If your ABC fluid is green (which it should be if its been serviced regularly) you should easily be able to tell if it is ABC fluid or engine oil. If your ABC fluid is black, then you need to replace it. Fluid can be bought in bulk (by either gallon or 5 gallon) on amazon fairly reasonable and it is an easy DIY to replace the fluid. Just make sure when you change the fluid to also drain the fluid that is between each valve block and strut by opening the bleeder screw located behind each wheel. If all you do is put new fluid in the reservoir you will not get this fluid changed out.

You have purchased a car where it is reaching the age where there is going to be a lot of maintenance moving forward (which is why they are so cheap compared to MSRP). Your SBC unit (around $800 wholesale and 3-5 hours labor to replace) is likely getting towards the end of its service life and with the torque the v12 makes your motor mounts too. The motor mounts on the v12 require removing the engine to replace and require 25 hours or so of labor. Other things you are likely to encounter is trunk cover flap hinges breaking, the front latching cylinder for the vert top leaking, and the soft close trunk closer ceasing to operate. While you are under the car check the conditions on the rubber bushings that are on the control arms attached to the front struts. On the heavy SL these usually only make it 40k miles or so before they are shot.

 

Thank you for very informative post, the way I see it I must:
Check if the oil is from the ABC system, or if actually is from rear main seal.
Proceed to change out the ABC fluid and filter anyway, and I should also replace hose 550 as a minimum.
If the leak is from the engine rear main seal, I assume that is a big job and the mechanics...tranny and all out??

 

rear main requires transmission removal. unless the leak is gigantic just wait till your transmission needs rebuilt to replace the rear main. rear main seal leaks are common.