BMW Valve Covers, Valve Cover Gaskets and Crankcase Ventilation (PCV)
Updated: Sep 2
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 valvetrain needs to stay lubricated from leaking or being sprayed out. 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!
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?
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.