OMG! OFHG (oil filter housing gasket)
Updated: Sep 2
A super common leak on pretty much most BMW 4 and 6 cylinder engines. 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 a gasket between those two as well. Also in this case engine coolant and engine oil pass through close to each other, sealed from each other by the gaskets.
Some housings are metal, others are plastic. Both have oil leaks.
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. In some cases the plastic housings actually crack or break where the seal channel is.
So what happens when these gaskets leak? 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, its a mess!!
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 "milk shake". 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!!! :
So 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.