Do you enjoy oil stains in your driveway and constantly having to pour more oil into your engine every month? We didn't think so. Here are a few of the common causes of oil leaks on modern Mercedes-Benz engines and how to service them.
Not all oil leaks are created equal. Some leaks plague certain engines more than others, so it's important to diagnose where your engine is leaking from before you dive into replacing every gasket and seal you can get your gloves on. One pro-tip is to clean off any surface you suspect is leaking oil using a brake cleaner and a rag. After the surface is clean, drive the car for a few hundred miles and check back on the area. If you notice fresh oil where two surfaces meet or oil "spraying" from another area, you know where the leak is and which seals/gaskets to replace.
Most Common Mercedes-Benz Oil Leak Locations
- Oil Separator
- Camshaft plugs - 30mm and 65mm
- Valve cover gaskets
- Oil filter housing and cooler gaskets
- Timing cover plug
Mercedes-Benz Engine Codes
To identify which engines are susceptible to certain oil leaks, refer to this list:
- M112 - V6 that ranged from 1997-2005, used in C-Class, CLK , E-Class, SLK, Chrysler Crossfire
- M113 - V8 used from 1997-2005, used in E-Class, ML, S-Class, G-Wagen, CLS
- M272 - V6 used from 2004-2011, C-Class, E-Class, SLK, CLK, R-Class, Sprinter, GLK
- M273 - V8 used from 2006-2014, E-Class, SL, S-Class, CLS, G-Wagen, ML, GL, R-Class
Mercedes-Benz Oil Leak Locations - M112, M113, M272, & M273 Engines
Mercedes-Benz Engine Oil Leaks - Rear
The most likely rear engine leaks include the oil separator and the cam plugs (30mm and 65mm). The oil separator is held onto the back of bank 1 (passenger side) with either 4 torx bolts or 4 external torx bolts. Remove the oil separator, replace, and clean the oil residue from the engine.
Depending on the model, there are usually two 30mm and one 65mm plug located on the back of the engine on both sides. The plugs will pop out with a screw driver and the new ones can be pushed on by hand. Be sure that they're pushed in flush with the engine as improper seating will result in, you guessed it, an oil leak.
Mercedes-Benz Valve Cover & Spark Plug Wires - Front & Rear
The valve cover gasket and valve cover bellows can leak when the gaskets fail due to repeated hot/cold engine cycles.
- Remove engine cover, air box and air duct tubing.
- Remove coil packs T30 bolts and spark plug wires. There are two spark plugs per cylinder. Label the coil packs "A" and "B". The best trick for getting the plug wires off without breaking them is to use a 17mm wrench. There is a special 17mm wrench with a bend that works great.
- Remove breather hoses (they are usually brittle so be prepared to replace them) from the valve covers.
- Remove the E10 Torx bolts and the valve cover.
- Replace your spark plugs now if you haven't already, since you have easy access with the valve covers off.
- Remove the T25 bolts from the breather covers and pry them off with a screwdriver.
- Remove all sealant from the breather cover.
- Apply new sealant to the channels of the breather cover, place valve cover down, and tighten T25 bolts by hand.
- Replace the valve cover gasket.
- Reinstall components. When installing the air box, lubricate the seal with some lube for the mass air flow connection. This will make it a lot easier to install .
Mercedes-Benz Engine Oil Leaks - Front
Oil Filter Housing & Gaskets
The driver's side front of the engine is where you will find your oil filter and housing. If you see oil at the bottom of the housing, you may need a new oil filter housing and cooler gaskets. The process of replacing these gasket is super easy:
- Drain oil
- Remove oil filter
- Remove oil cooler
- Remove oil filter housing nut with a 46mm socket.
- Replace the gaskets
- Reinstall parts, replace oil filter, and oil.
- Clean oil residue
Timing Cover Plug
If your timing cover plug is leaking, it's likely due to a bad seal. Luckily, replacement could not be easier:
We hope this article was helpful in helping solve your Mercedes-Benz oil leak woes. Check out the link below to get the seals and gaskets used in this article, as well as other parts for your Mercedes-Benz. If you have any questions, be sure to leave them in the comments section below.
Jerry is a Master BMW technician from Boston, MA with 10 years of automotive experience. He currently owns a BMW X5 3.0i, 540i, and a bass boat. During the week he spends his time in the shop fixing BMWs and likes fresh water fishing on the weekends.