If you find an oil leak down the left side of your engine or what looks to be the oil pan, it may be the oil filter housing gasket. The oil filter housing uses a rubber profile gasket and over time it hardens and leaks. When trying to locate the source of an oil leak, always start at the top of the engine, locate any oil covered areas, the cleanest oil covered area is likely the source of leak. You will need the oil filter housing profile gasket, and for M54 6-cylinder engine models the VANOS oil line sealing washers. It's not a bad idea to grab oil and a filter too, changing the oil is only a few more steps while doing this repair. This article shows the M54 engine. NG6 normally-aspirated engines are similar and covered in a separate article.
Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.
Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.
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Remove alternator. See our tech article on alternator replacing. Place an oil drain pan under left side of engine. Remove the power steering reservoir 13mm fasteners (red arrows0, then lay the reservoir aside.
Using a 19mm wrench, remove the VANOS oil line banjo bolt (red arrow), (below oil filter housing). Cover line and opening to prevent dirt from entering VANOS system. Be sure to replace sealing washers when reinstalling.
Remove three power steering pump 13mm fasteners (green arrows). Fasteners are different lengths, mark locations for help when reinstalling. With fasteners removed, push power steering pump down and away from the oil filter housing bracket.
Clean engine sealing surface (purple arrow), inspect alignment dowels (green arrows), they help you align housing when reinstalling. Be sure they are in good condition and installed in engine straight. Install new gasket into oil filter housing. Then install oil filter housing onto engine. Be sure to align dowels properly.
Install oil filter housing fasteners in previous locations. This photo shows orientation of fasteners, top to bottom. Tighten oil filter housing fasteners in a crisscross pattern. Install power steering pump to oil filter housing and tighten fasteners. Install VANOS oil line using new sealing washers. Reconnect oil switch electrical connector. Then reassemble engine in reverse order of procedure. Remember to top up engine oil and check for oil leaks when complete.