Here’s How Neglecting A $36 Gasket Can Destroy A $22,000 BMW Engine

Are you ignoring something on your car right now? If it’s older, you probably are. Maintenance is simply a fact of older vehicle ownership, but like a toothache, the longer you put off that maintenance, the more painful it gets. Sure, you’re likely well aware of the lethal potential of failing wheel bearings and bad brakes, but sometimes a seemingly innocuous problem can lead to big troubles. Something as simple as a gasket, especially when it comes installed on say, a BMW.

Today, we’re talking about a problem that can afflict BMW N52, N54, N55, and S55 inline-six engines, but only if their owners wilfully ignore warning signs. It’s a problem that can be fixed for cheap early on, but once it comes to a headwind, it could leave owners with multi-thousand-dollar repair bills. All over a gasket that costs around $36.

To use a cartridge-style oil filter on these engines, BMW decided to go top-mounted, and top-mounting requires an oil filter housing. It’s a convenient thing most of the time, as the cartridge-style filter doesn’t trap used oil like canister filters do, and it makes it easy to inspect the filter media. However, there is a downside to BMW’s implementation here.

The filter housing requires a gasket, of course, and gaskets don’t last forever. So eventually, the oil filter housing gasket will start to weep. Once that weep becomes a drip, oil leaking past the top-mounted oil filter housing gasket can find its way onto the serpentine belt. Normally, when oil gets on a serpentine belt, it simply slides off and shreds, causing a mess and necessitating a tow, but not causing major damage. However, the clever engineers at BMW have found a second failure mode.

When the serpentine belt slides off, it can and very likely will go behind the crank pulley and wrap itself around the back side of the crank pulley bolt. From there, it can force its way into the front main seal of the engine and around the crankshaft, potentially causing engine-killing damage.

If a big enough chunk of belt slips its way through the front main seal and into the timing chain cover, it can get lodged in the timing chain, causing the engine to jump timing. Since this is an interference engine, by the powers invested in me, I now pronounce you piston and valve. You may now kiss the valve.

If this worst-case scenario happens to a BMW N52, N54, N55, or S55 inline-six found in almost every inline-six-powered BMW between 2006 and 2016, you will need to start shopping around for a new engine. Considering a new replacement S55 costs upwards of $22,000, this can be a seriously pricey proposition.

However, let’s say you do get lucky and don’t grenade your engine. Well, you’re still in for a world of financial pain, because although the parts are cheap, the labor is anything but. The front crankshaft seal itself is a three-hour job, and that’s just for inspection. If your belt made it past the front main seal, dropping the oil pan is a five-hour job on an F30 335i, and pulling the timing cover calls for 8.9 hours of labor. At the same time, you’ll still need to replace the leaky oil filter housing gasket, so tack a few hundred dollars in labor on top of the thousands spent fishing bits of belt out of the engine.

If you want a really good look at what can happen if the belt shreds on one of these engines, Charlie’s Foreign Car Service has the great Youtube video that I’ve embedded above. Note the sheer level of disassembly required to clean this mess up, along with the fact that even if your engine doesn’t jump timing, belt material can still find its way into the oil pickup tube, potentially clogging the tube, starving the engine of oil, and seizing the engine.

Perhaps unsurprisingly, this is a commonly reported issue in the BMW community, including reports of engine issues following a belt shredding, such as this forum thread on Bimmerpost:

Here’s an example of it happening on an expensive S55 M-car engine, courtesy of another Bimmerpost thread:

That’s belt material wrapped around a crank hub like seaweed. Terrifying stuff, and a seriously expensive issue to fix.

If you’ve replaced your belt and tensioner on schedule, this issue can be easily mitigated with a little vigilance, some cheap gaskets, and a few hundred dollars of labor. A new oil filter housing gasket is $35.99 from our friends at FCP Euro. That sort of money barely buys you a film screening ticket and popcorn these days.

Sure, not every engine will have this exact same ridiculous cascading failure mode, but deferred maintenance piles up. There’s no free lunch in vehicle ownership, you either pay now or pay more later. For everyone’s sake, if something is mechanically wrong with your ride, fix it ASAP. Chances are, you’ll be glad you did.

(Photo credits: BMW, eBay seller, Charlie’s Foreign Car Service/YouTube)

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