A super common engine oil leak on pretty much most BMW 4 and 6-cylinder engines. The notorious oil filter housing gasket, and sometimes also known as an oil filter stand gasket. M43, M44, M54, N51, N52, N54, N55, N20, B46, B48 and B58. Most will have this leak at some point in their life. But, what is it? And should you worry about it?
Well, the oil filter housing is just that, it houses the oil filter. This housing is a separate component that bolts up to the side of the engine block or cylinder head. Engine oil has to pass from the engine or cylinder head to that housing and then back. The oil filter housing gasket goes between the housing and the engine or cylinder head and is there to seal the connection between the two.
On some engines, there is also an engine oil cooler attached to the oil filter housing that needs coolant to pass through to cool the engine oil. In this case, there's an oil cooler gasket between the two. Also in this case engine coolant and engine oil pass through close to each other, sealed from each other by the gaskets.
The most common failure on the oil filter housing is the oil filter housing gasket itself leaking. Another failure point is the oil filter cap O-ring leaking. This frequently happens when super cheap aftermarket oil filter kits are used and the oil filter cap O-ring is replaced by a cheap O-ring from the kit that does not seal properly (another reason we recommend getting our oil changed using BMW original parts or BMW OEM supplier parts). Some housings are metal, others are plastic. Both types leak engine oil. Here are a few images of what these different BMW engine oil filter housings look like:
So why does the oil filter housing gasket leak?
Heat and age mostly. Over time the gaskets age, get brittle, and can no longer seal properly. The same happens to other gaskets on your BMW, like the valve cover gasket. In some cases the plastic housings actually crack or break where the seal channel is, causing an engine oil leak.
What happens when these gaskets leak oil? And when should I fix it?
It depends... Sometimes they just seep a little bit and the oil that comes out collects dirt. This isn't a big deal, as long as it doesn't get worse. But other times, it's a mess!! You spend good money on the right engine oil, might as well keep it in the engine right!
On some engines where the housing is mounted to the head above the drive belt oil starts to leak down the front and along the bottom of the engine. Covering all the splash panels. In some cases the engine drive belt gets so soaked in oil it can come apart into pieces. Pieces that can get sucked into the engine through the front main seal and eventually into the engine oil pump pick up causing low oil pressure. Not good!
On others, it can cause what is known as "intermix" or "milkshake". This is where the engine oil and coolant intermix causing the engine oil to thin out with coolant, which is definitely not good for your bearings, as well as engine oil to get pushed into the cooling system, coating everything with engine oil where engine oil doesn't belong. This is quite the clean-up job too!
Here's a video of a B46 we had recently at Driven SD with intermix. Yum!!! :
How involved is this gasket replacement?
Again, depends on the engine. On some, it requires intake manifold removal, on others removal of the alternator and drive belts. It's a decent-sized job. If you want it done right, Driven SD is here to help.
Oil filter housing leak repair cost
The cost to repair a leaking oil filter housing also varies with each vehicle and engine, but the typical range in our area (San Diego) is anywhere from $400 to $1500.
Check out some of our other articles like where to get BMW suspension repairs in San Diego and learn about BMW spark plugs and Maximizing Your BMW's Performance with the Right Fuel.