Crankcase ventilation cylinder head cover
Crankcase ventilation cover (engine breather cover) is a very common source for oil leaks on Mercedes M112 V6 and M113 V8 engines. Just pull the top cover off your engine and look. Even cars with low mileage may have oil seeping out the breather covers on the top of the heads. When the oil gets on exhaust manifold, it creates smell that can be felt even in the cabin. Resealing the leaking breather chamber covers on top of engine is easy way to fix oil leak.
This is the job any owner of a 1998 to 2006 Mercedes with a V6 (M112) or a V8 (M113) engine will have to deal with at some point. Doing a proper reseal on these covers is not hard but it is tedious if you don't want them to leak again. This is one job if you want it done right you should consider doing it yourself!
Clogged ventilation valve
If engine oil is not regularly changed, the ventilation breather valve hole can become clogged which will result in water condensate being accumulated on the top of crankcase and visible on the engine oil cap. Proper cleaning of the milky water residue requires it to be cleaned also from the cylinder head cover. This may be a good moment to also replace the cylinder head cover gaskets.
Several parts will be needed for replacement. Several resealing kits are available:
Below are the part numbers for each part.
The 5 original aluminium bolts will have to be replaced with updated stainless steel ones as the old will snap if trying to reuse them. The replacement stainless steel bolts have a 5 mm hex head rather than a torx head.
The bolts correspond to M5x18 specification and their part number is N000000004436 (~2 EUR/piece).
Proper sealant must be used. OEM sealant is Loctite 5970 which is a silicone sealant and cures on exposure to moisture in the air to form a tough rubber gasket. The product is designed primarily for flexible flange sealing. It is ideally used where high vibration or flexing occurs. It is tack-free after just 25 min. The product can be used on machined or cast surfaces, metal, plastic or painted parts.
- A003989982010 50ml (OE) - EUR 26
- Loctite 5970 300ml (OEM) - EUR 18
- Elring Dirko 70ml - EUR 5
It must be made sure that the sealing surfaces are ABSOLUTELY clean of any dirt, oil, or moisture BEFORE applying the new sealant. Mercedes instructions recommend using Loctite 7200 to remove old pieces of gasket sealant and Loctite 7063 to prepare surface for the new sealant.
Over time the rubber hoses get hard and cannot be removed without breaking. It is therefore recommended to replace 4 hoses and 3 connectors. Connectors are usual in good condition and require no replacement. For some of the hoses FEBI BILSTEIN is OE mananufacturer.
Engine 112 and 113 (S350/S500):
Remove/install cover for crankcase ventilation (WIS instruction)
ENGINES 112, 113
|Shown on engine 113:
|Sealant path - Shown on engine 113:
- Aluminum bolts (1). Installation: Install new bolts.
- Clean. When cylinder head covers are installed, cover oil ducts with rags. Do not use any sharp-edged tools or abrasive paper as this will damage the sealing surfaces. Oil channels clogged with sealant will damage the engine. Cleaning materials: Loctite 7200 and Loctite 7063 cleaning spray 150 ml (A001986717110).
- Sealant. Apply a 2.0 mm thick bead of sealant (A), observing the bolt holes (arrow). Do not spread the silicone bead. Process sealant within 10 minutes. To avoid leaks, use only the silicone sealant specified in the repair materials - Loctite 5970 sealant (A0039899820)!
- Bolt, crankcase ventilation cover to the cylinder head valve cover: 4 Nm (Engine 112 and 113)
Cylinder head cover
Cylinder head cover is also popular source for oil leaks on M112 and M113 engines. It is highly recommended to use OE gasket as it provides the best quality and requires no additional sealant.
Cylinder head cover gaskets
Engine 112 (S350):
- A1120160221 Cylinder head cover gasket (left) - EUR 20
- A1120160321 Cylinder head cover gasket (right) - EUR 20
Engine 113 (S500):
- A1120160221 Cylinder head cover gasket (left) - EUR 22
- A1120160321 Cylinder head cover gasket (right) - EUR 22
Remove/install cylinder head cover (WIS instruction)
|Shown on engine 112.945:
- Remove engine trim panel with integrated air filter (1). Unclip covering on front side of engine. Remove air filter by pulling vertically up and off the cylinder head covers.
- Remove air filter (Model 215.374, 220.074/174)
- Unscrew guide tube for the automatic transmission oil dipstick
- Detach right ignition coils (4), left ignition coils (5) on right cylinder head cover (2) and left cylinder head cover (3). Except engines 112.911/914/915/917/954, Engine 113.969.
- Disconnect spark plug connectors. Installation: Observe marking for spark plug connectors on the cylinder head covers and ignition coils.
- Pull off vent hoses on right connector (6) and on left connector (7) of the right cylinder head cover (2) and left cylinder head cover (3).
- Pull off engine vent hose on left connector (8) of left cylinder head cover (3).
- Disconnect fuel line at fuel rail. Only on vehicles with rigid fuel line and: Model 211.061/065/070/076/276, Model 215.374, Model 220.074, Model 230.474/475. Release fuel pressure through service valve!
- Remove right cylinder head cover (2) and left cylinder head cover (3). Installation: Check cylinder head covers for leaks, see: Ensure cylinder head cover gasket is correctly installed.
- Install in the reverse order
- Check for leaks with engine running
- Cylinder head cover bolt: 9 Nm (Engine 112 and 113)
- Bolt, ignition coils to cylinder head cover: 8 Nm (Engine 112 and 113)
- Fuel feed line to fuel distributor: 38 Nm (Engine 112 except 112.945/951/960/961)
- Fuel feed line to fuel distributor: 38 Nm (Engine 112.945)
- Fuel feed line to fuel distributor: 35 Nm (Engine 112.960/961 AMG)
- Fuel feed line to fuel distributor: 38 Nm (Engine 113.940/941/942/943/944/945/946/948/960/961/962/963/964/965/966/967/968/969/971/980/981/982/984/986/988)
- Fuel feed line to fuel distributor: 38 Nm (Engine 113.987)
- Fuel feed line to fuel distributor: 38 Nm (Engine 113.990/991)
- Fuel feed line to fuel distributor: 38 Nm (Engine 113.992/993/995)
Ensure gasket of cylinder head cover is correctly installed: