Valve Cover Assembly for BMW Z Series E85/6 (2003-2008)

• All-in-one valve cover overhaul
• Preventative replacement saves time and trouble later on
• Includes new oil separator system
• Replace valve cover gaskets before a leak becomes worse
• Replace valve cover before it cracks

For the 2007 model year BMW switched to a plastic valve cover on the N51 and N52 engines. As we have seen over time the plastic can crack which leads to oil leaks, vacuum leaks, poor running, and other issues. Unfortunately, it's not just the gasket that needs periodic replacement but the entire valve cover itself. This kit includes a new valve cover, gaskets, eccentric shaft seal, and hardware. The valve cover also incorporates the oil separator which is not a replaceable item on its own. So a complete valve cover replacement will tackle multiple problem areas at once. The valve cover is the same for N51 SULEV and N52 engines.

Cracked Valve Cover. The plastic used for the N52 valve cover is thin and weak in certain spots. This makes it prone to hairline or larger cracks that will leak oil and cause vacuum leaks. You might also notice rough running, especially at idle. Often a technician will go looking for a failed ignition coil, spark plug, or failed vacuum hose on the engine. And without a fault code to assist in diagnosis this can often mean wasted time and money. A cracked valve cover is a new problem area that many techs don't think to check.

Oil Separator/Crankcase Vent. BMW integrated the oil separator system into the valve cover on these later engines. An internal manifold creates a cyclone effect and centrifugal force separates vapor from the liquid oil. The liquid oil is supposed to drain through the valve cover and back to the oil pan while the remaining vapor is burned up during combustion. It's a very efficient and environmentally-friendly design with very few moving parts. Unfortunately it's not perfect and eventually the internal passageways will become clogged. This problem is made worse in cars that have short drive cycles, sit for long periods of time, do not have frequent oil changes, do not see regular runs to redline, and cars in freezing climates. If the engine never reaches optimal operating temp the oil remains in liquid form or becomes sludge. This is bad news for the entire engine, leading to fouled spark plugs, rough running and misfires and even premature failure of catalytic converters and oxygen sensors. Since the oil separator system in the valve cover is not available on its own, and cleaning it is nearly impossible, the complete replacement of the valve cover is the only option. Other oil vent tubes and vacuum hoses are also recommended to get replaced at the same time.

Valve Cover Gaskets. As with any rubber part, failures occur when the rubber becomes dry and brittle. The pliable rubber no longer forms a seal between the cylinder head and valve cover where it will develop an oil leak. Valve cover gaskets that leak can allow oil to seep into the spark plug holes and contaminate ignition coil boots and plugs. That can lead to rough running and misfires. A new valve cover includes new gaskets.

Eccentric Shaft Seal. The seal for the eccentric shaft sensor is a known spot for oil leaks. When the seal to the valve cover fails oil can end up in the sensor itself and ruin the sensor (an unecessary $300 expense). Usually a new seal (o-ring) will stop the leaks but sometimes the valve cover is at fault too. A new eccentric shaft seal is included.

All new hardware is included to avoid re-using and over-tightening the original bolts (they have a very low torque rating).

Replacement requires accessing the rear of the engine with a lot of the upper plastic shrouding removed. The vent hose on the valve cover should be replaced as it is almost always broken anyway (#11157559528). The metal fuel line must also be removed and disconnected from the fuel injectors. Professional installation is encouraged if you have never done this kind of work before. Serious DIY types should have a Bentley Service Manual to use which greatly explains the process. You may also want to combine this work with the oil filter housing gasket replacement.

There is no maintenance or replacement interval for the N52 valve cover. However, we have seen cracks and other failures in the 50,000-90,000 mile range. Our best advice is to plan on a major top end overhaul around the 70-80,000 mile mark. There's no mechanical downside to replacing it as prevention and it will make the engine run better and last longer.

This item fits the following BMWs:
2008-2012 E82 BMW 128i
2007-2011 E90 BMW 328i 328xi 328i xDrive - Sedan
2007-2012 E91 BMW 328i 328xi 328i xDrive - Wagon
2007-2013 E92 BMW 328i 328xi 328i xDrive - Coupe
2007-2013 E93 BMW 328i - Convertible
2008-2010 E60 BMW 528i 528xi 528i xDrive
2011 F10 BMW 528i
2007-2010 E83 BMW X3 3.0i X3 3.0si
2007-2008 E70 BMW X5 3.0si
2007-2008 E85 BMW Z4 3.0i Z4 3.0si
2009-2010 Z4 BMW Z4 sDrive30i