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BMW Valve Covers, Valve Cover Gaskets and Crankcase Ventilation (PCV)

Updated: Jan 3


BMW 328i N20 valvetrain with valve cover off in San Diego

Are you smelling a burning smell while you drive? Or are you getting some oil spots in the driveway? Maybe your engine is howling at idle? It just might be that your BMW needs a new engine valve cover or valve cover gasket.


What is the valve cover on a BMW?


Think of a valve cover as a lid for your engine. It sits on top of the cylinder head covering up the valvetrain to keep all that oil that the valve train needs to stay lubricated from leaking or being sprayed out. The valve cover is usually held down by valve cover bolts. Between the valve cover and cylinder head is a rubber gasket that seals the connection between them. On BMWs 3, 4, and 6 cylinder engines there's one valve cover, since they are an inline design. On the V engines like the V8, V10 and V12 you have two valve covers, one on each bank.


How can a valve cover or valve cover gasket cause a burning smell?


If your BMW valve cover or valve cover gasket starts to leak, there's a very good chance the oil will be dripping on your exhaust and burning off, causing the smell. We've seen leaks so severe it's impressive that they hadn't caught fire! Automotive valve cover gaskets leaking is one of the most common engine oil leaks. You can have a faulty valve cover gasket, but usually they leak from age. The old valve cover gasket gets hardened over time and no longer seals like it should.


What about those oil spots?


It could be any number of things leaking on your engine, but a valve cover leak is very common on a BMW. As your BMW ages those valve cover gaskets harden from many heat cycles and eventually can't properly seal anymore. And since all BMW inline engines sit at angle to save space, and the V engine heads sit at an angle, the leak will usually start on the downward slope of the valve cover. It's rare, but the valve cover can also crack causing a leak, so a proper diagnosis is recommended.


How can a valve cover make my BMW howl?


A BMW B46 valve cover during replacement at Driven Sd in San Diego

In most modern BMW engine designs the crankcase ventilation system is integrated into the valve cover. This system is designed to put the crankcase into a vacuum to pull blow-by gases out of the crankcase and route it into the intake while also separating any engine oil out of the gases and routing it back to the oil pan. This is known as Positive Crankcase Ventilation or PCV. The amount of vacuum generated in the crankcase is regulated by a crankcase ventilation valve or PCV valve. It's fairly common on BMWs that the crankcase ventilation valve fails and causes excess vacuum in the crankcase. This then causes air to get sucked into the crankcase past the front and rear crankshaft main seals which will cause a howling noise either during idle or just as your car is shutting off for auto start/stop. In some cases the vacuum can get so high that engine oil will get sucked into the intake causing smoking from the exhaust as the engine burns oil.


How hard is a valve cover or valve cover gasket replacement on a BMW?


It really depends on the engine. Some are easy, some are hard. Some require a few extra parts. But here at Driven SD we've done them all, and can help with yours too.


And speaking of keeping that oil in the engine find out why using the right oil in your BMW is important and OMG! OFHG (BMW oil filter housing gasket) that like to leak. We hope you found this article to be informative. Don't forget to check out some of our other BMW articles like "Why Using the Right Engine Oil Matters for Your BMW" and “Where Can I Get BMW Suspension Repair in San Diego?”.

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