The BMW E90 is a popular and reliable vehicle, but one common issue that owners face is a valve cover gasket leak. This can be frustrating, as it can lead to oil leaks and other problems that can damage the engine over time. In this guide, we’ll take a closer look at the causes of this issue, how to fix it, and the differences between the plastic and magnesium valve cover.
What is a Valve Cover Gasket Leak?
The valve cover gasket is a small piece of rubber or silicone that seals the gap between the valve cover and the engine block. It’s an important component, as it prevents oil from leaking out of the engine. However, over time, the gasket can become worn, cracked, or damaged, leading to leaks. When that happens, you’ll need to replace the gasket.
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What Causes a Valve Cover Gasket Leak?
There are several factors that can contribute to a valve cover gasket leak. One common cause is age and wear and tear. As the gasket gets older, it can become brittle and less flexible, making it more prone to cracks and leaks. In addition, exposure to heat and engine fluids can also cause the gasket to deteriorate.
Another factor that can contribute to a valve cover gasket leak is improper installation. If the gasket is not installed correctly or is damaged during installation, it may not seal properly, leading to leaks.
Symptoms of a Valve Cover Gasket Leak
When the valve cover gasket leaks on the E90, it can cause two distinct symptoms. The first one is oil leaking around the valve cover perimeter, and that one is fairly benign. The other is a rough idle or even misfire.
The first symptom is fairly obvious. However, sometimes the gasket can leak in the rear of the engine, which makes it extremely difficult to spot. You’ll need to rely on checking the oil levels and other methods to spot this type of leak.
As for the rough idle and misfires, this happens when the oil gets into the spark plug bore. The N52/N54, like many similar engines, features dedicated gaskets around each spark plug bore that prevent the oil from the valve train area from reaching the spark plug. These gaskets fail just like the main valve cover gasket. When oil seeps into the spark plug bore, it can penetrate into the combustion chamber or cause issues with the ignition coil-spark plug connection. That’s usually when you’ll experience misfires, rough idling, and other similar symptoms.
Plastic vs. Magnesium Valve Covers
When it comes to valve cover gasket leaks on the BMW E90, there is a difference between plastic and magnesium valve covers. The E90 came with both types of covers depending on the version of the engine you have, and each has its own advantages and disadvantages.
The important thing to note is that magnesium valve covers came with aluminum screws, while plastic valve covers had steel screws. This is an important bit of information for two reasons.
For one, aluminum screws shouldn’t be reused. When installed, these screws deform ever so slightly, which can cause issues when you go and try to reuse them. The resulting issues may vary from oil leaks to snapped screws.
On the other hand, magnesium valve covers require aluminum screws. BMW chose these for a reason. When magnesium comes into contact with steel, it reacts and begins to corrode. That’s why it’s essential that you know what type of valve cover you have on your car before you go about replacing the gasket.
Get aluminum valve cover screws for your E90.
How to Fix a Valve Cover Gasket Leak
Fixing a valve cover gasket leak is relatively straightforward, but it does require some mechanical knowledge and tools. On the E90, replacing the valve cover gasket involves disconnecting the battery, removing all the electrical connectors, and fuel rail harnesses, unplugging the ignition coils and removing them, and more.
We’ll do a detailed guide on how to replace the valve cover gasket on the N52/N52 engines in the future.
Use Quality Valve Cover Gaskets for Your BMW E90
If you own a BMW E90 and are experiencing a valve cover gasket leak, don’t panic. This is a common issue that can be fixed relatively easily with the right tools and knowledge. By following the steps outlined above, you can fix the problem and get back on the road in no time. And if you’re considering replacing your valve cover, be sure to know which type of valve cover matches your engine.
We can help with that! Head over to our store, select your vehicle using our vehicle selector tool, and we’ll show you valve covers as well as valve cover gaskets that are a perfect match for your car!
