Why You Can't Ignore An Oil Filter Housing Leak On An N51, N52, N54, or N55 Engine

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I've already outlined why it's critical to repair an oil filter housing leak on any N5X engine (N51, N52, N52N, N54, or N55). I've even highlighted how to fix the issue yourself in a  DIY article. Now, I have the photos to back up how bad this can be. And it's not pretty.

Oil leaks are a nuisance, but most are harmless. I haven't seen too many higher mileage BMW's that don't have some kind of oil leak that goes unrepaired. The truth is, most are difficult to fix and less caring owners simply don't want to invest the money into making the repair. If there is one oil leak on the N5X family of engines that is critical to address, it's going to be the oil filter housing gasket. This rubber gasket seals the oil filter housing to the cylinder head and is a super common source of oil leaks on most BMW engines where the oil filter housing bolts to the engine block or cylinder head.


Now, why is this a serious issue on the N5X family of engines? Well, simply put it can lead to engine failure. Yes, you read that correctly, it can in fact lead to engine failure and I have photographic evidence from an N54 engine that met its demise from what started with an oil filter housing leak. See the pictures below:


What are you looking at are shards of serpentine belt material that are inside the engine. How does serpentine belt material end up inside an engine? It's primarily due to the design of the harmonic balancer/crank pulley assembly on the N5X engines and the position of the serpentine belt relative to the engine block. The oil filter housing leak when severe enough can create a trail of oil all the way down the front of the timing cover eventually coating the serpentine belt and crankshaft pulley. Once oil is on the serpentine belt and the crank pulley portion of the harmonic balancer it is almost inevitable that the serpentine belt will slip off. Since the harmonic balancer is in front of the crank pulley the serpentine belt has no where to go but back towards the timing cover if it slips off. Once it slips off the crank pulley, essentially it shreds the belt and forces the pieces of belt through the front crank seal. 

Unfortunately, the N54 in the photos above suffered this failure. It appears that a new front crank seal was installed and the oil leak was repaired. However, whoever made the repair didn't bother to inspect as to whether the serpentine belt was sucked inside the engine (they probably thought it was flung off). This engine has a severe rod knock and once it was opened up it became pretty clear that the amount of debris in the oil pickup tube likely created an oil starvation issue which eventually caused rod bearing failure. There is probably other damage in this engine as well based on the amount of debris found inside of it.

The takeaway here, is it's important to not overlook an oil filter housing leak on these engines. Now, if there is a small leak I'm not telling you to pull over and get the vehicle towed. What I am saying is what starts off as a small leak almost always gets worse. In the case of N5X engines a severe oil filter housing leak that can be repaired with a relatively inexpensive gasket can end up costing you thousand of dollars later on or worse, a complete engine replacement. 

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