N51/N52N Valve Cover Gasket Replacement

Blog Feature

bmw-valve-cover-gasket

This DIY is going to be centered around handling the replacement of a valve cover gasket (and associated gaskets) on N51 and N52N engines. Unlike early N52 engines, which used a magnesium valve cover and had an external crankcase vent valve, the updated version features a plastic valve cover with an integrated PCV valve. One thing to note about the N51 and N52N engines is that the valve cover screws DO NOT need to be replaced, unlike the magnesium valve cover which requires special aluminum screws (which are also prone to breaking), the N51 and N52N engine's valve cover has encapsulated hardware.

Before you get started, I must stress that this is not a basic or straight forward job; it will require basic automotive skills and some finesse. Depending on the vehicle you're working on, you may have more or less stuff to move out of the way before you can access the valve cover. In this DIY, we worked on an E92 3-series with an N51 engine. I was able to complete the job in about 5 hours doing it my first time, however it may take you more time or less time based on your experience:

Tools needed:

  • E8 socket
  • E10 socket
  • T30 torx socket
  • 4mm allen socket
  • 3/8 univeral joint
  • 1/4" univeral joint
  • 3/8" extnesoins
  • 1/4" extensions
  • 3/8" ratchet
  • 1/4" ratchet
  • 3/8" metric socket set
  • 1/4" metric socket set
  • Pry tools

Step 1: Remove all covers

This step is going to vary based on what car you own. For an E8X 1-series or E9X 3-series, you will start off by removing the cabin filter housing, AUC sensor (if equipped), strut brace (if equipped), engine acoustic cover, etc. Basically, this first step is to open the engine bay up and get the other equipment out of the way. On the N51/N52N engines in the E8X 1-series and E9X 3-series, you will find that there's a lot of stuff that must be removed before you can get to the valve cover.

bmw-e90-engine-bay

This is what the engine bay will look like when everything is out of the way:

bmw-e90-engine-bay

Step 2: Disconnect the battery

At this point, it's a good idea to disconnect the battery ground cable in the trunk to make sure you don't inadvertently short anything out as you will be moving harnesses and disconnecting a lot of electrical components in this job. All you need is a 10mm box wrench or socket on a ratchet. Once the bolt is loose, pull the terminal connector off the lead on the battery and put off to the side:

bmw-e90-battery

Step 3: Move everything out of the way

At this point, it's time to start disconnecting all of the electrical connections. On the intake side of the engine, you will need to disconnect the fuel injector harness, oil pressure sensor, oxygen sensor connectors, and anything else in the way. The fuel injector harness is one plastic housing with individual connectors that plug into the injectors. Using a small pick tool, pull the small metal clips up and back. Make sure you do not lose the clips as finding replacements in next to impossible.

bmw-injector-harness

Once all the clips are pulled back, pull the injector harness up and out of the way. When doing this, make sure that there is not too much tension on other parts of the harness. If there is, trace the wires to the source of the tension and disconnect if possible. You will also need to remove the e-box cover on the passenger side of the engine bay. The locks on this cover slide into the unlock position, allowing you to lift the cover out of the way. You will have to slide the harnesses that sit in the box out of the way later on as well.

bmw-wiring

During this step, unplug the Valvetronic servo motor (large silver component on the side of the valve cover) as well as the Valvetronic sensor connector from the front of the valve cover. It's also a good time to unplug the ignition coils and remove them. Simply flip the tabs on the coils up and pull the electrical connector out. Gently lift the ignition coils out of the valve cover.

There is a breather hose on the back of the valve cover. Be careful when removing this as it can be fragile with age. Simply press the tabs inward with your fingers and push the hose off the nipple on the valve cover. If it's not moving, do not pry on it with any tools. Take your time and make sure you don't break the hose.

On the N51 and N52N engines, there are metal spark plug sleeves which help seal off the spark plug tubes. These sleeves are one time use only and must be removed to have enough room to remove the valve cover. Using a pair of snap ring pliers, squeeze the gap in the sleeves together and pull them out. This is what they look like when installed:

bmw-spark-plug-wells

Step 4: Only applies to N51 engines

The difference between N52N and N51 engines is that N51 engines are SULEV certified, meaning they have more aggressive catalyst systems and a sealed fuel system. In addition, they also have a secondary air injection system. The secondary air injection valve and hose will need to be removed in order to get the valve cover off. The secondary air injection hose is your standard issue type of quick disconnect hose. Simply press the tabs in and twist off. Be careful when doing so as the plastic hose can become brittle with age. To remove the secondary air injection valve on the side of the cylinder head you will need to use a universal joint and extension to gain access to the 10mm nuts that hold it on. Basically, find the combination of tools that works for you and make sure you don't drop the nuts into the engine bay.

With everything disconnected and the harness moved out of the way, this is what your engine bay will look like:

bmw-valvetronic-motor

Step 5: Remove Valvetronic motor

You can remove the Valvetronic motor safely in two ways. If you happen to have INPA or ISTA software, you can set the motor into a service position where it does not have tension on the eccentric shaft. This is the preferred method, but you can also do it the low-tech way. There is a spot on the side of the Valvetronic motor where you can insert a 4mm allen socket. Spin the motor to the right (clockwise) until you feel some tension. Once you feel tension stop, leave the socket in the motor. Next, you will be removing the e-torx screws that hold the motor to the valve cover. There is one just under the motor and two on the mounting flange. To remove the lower torx screw you will need to use 1/4" tools. Remove the lower screw entirely. The two larger screws that secure the motor to the valve cover loosen slightly. At this point you will spin the Valvetronic motor with the 4mm socket to the left (counter clockwise) and the motor will start to back itself out of the valve cover. As the Valvetronic motor is coming out gradually back the main torx screws out. What you do not want to happen is have the motor eject out of the valve cover and get damaged. Think of the larger mounting screws on the flange like the safety pin on a grenade. Once the motor is completely out, place it somewhere safe.

bmw-valvetronic-motor

Step 6: Remove the valve cover

The valve cover is held on with a series of torx screws that sit around the perimeter of the valve cover. The torx screws in the back are going to be brutal to gain access to; this is where your universal joints and extensions come into play.

Pro-Tip: Do not drop your E8 torx socket when working on the back of the engine. Finding it will take a lot of time and will involve removing the under tray. Ask me how I know.

Basically, go around the perimeter of the valve cover loosening all the torx screws first. These screws are encapsulated and will not come out of the valve cover. The housing the screws are in may come out of the valve cover, but you can slid them back into place. For the screws in the back, take your time and use whatever extensions/methods you can pair to get them out. Once you undo all of the perimeter screws, double check to make sure nothing is in the way.

There are three studs in the center of the valve cover that can be removed with regular hex sockets. Make sure you have deep sockets for this as one of the studs is pretty deep. Two of the studs are grounding points for the ignition coil harness. These three inner bolts also thread into the cylinder head and help seal the valve cover around the spark plug tubes.

Note: On some vehicles the coolant expansion tank hose may be in the way. Simply disconnect the hose and put it off to the side.

Do a final check around the perimeter of the valve cover and make sure every fastener has been loosened before you attempt to remove the valve cover. Note that a faulty Valvetronic motor seal will cause oil to pool in the center cavity of the valve cover. Be aware of this when removing the valve cover as it will likely spill everywhere. Also, be careful when pulling the valve cover out as there is not a ton of room to work with. I basically lifted from the front and angled it towards the passenger side.

bmw-e90-engine-bay

The e-box and the windshield cowl interfere slightly but with enough finesse, you can get the valve cover out without damaging it or breaking anything else. Below is what you are left with when the valve cover is off the engine.

bmw-e90-engine-bay

If you've ever wondered how the valvetronic system works, the motor has a corkscrew that turns which in turn changes the position of the eccentric shaft. This will either increase or decrease the lift of the intake valves. This is how it mounts:

bmw-valvetronic-motor

Here is a good video showing how the Valvetronic system works:

 

Step 7: Replace the valve cover gasket

Have a break and pat yourself on the back. You have reached the halfway point in the job. If you're replacing the entire valve cover, you don't need to worry about these steps. If you are reusing the original valve cover, you will need to remove the old gasket as well as the three individual spark plug tube seals. This step is relatively straight forward.

First, clean the valve cover as best as you can. Brake parts cleaner works well for this. You will want to clean the mating surfaces on the cylinder head with lint free shop rags. Make sure no left over gasket material or oil is on the surface as it can prevent the gasket from sealing properly.

The replacement valve cover gasket has a tab on it with the short seven digit BMW part number. If you're having trouble orienting the new gasket, this tab is located on the intake side of the valve cover towards the front like this:

bmw-valve-cover

Push in the new spark plug tube seals. They only fit one way, so don't worry about mixing them up:

bmw-valve-cover

The Valvetronic motor gasket and Valvetronic sensor seal can be replaced once the valve cover is installed. This makes things much easier later on and prevents inadvertently damaging the seals (particularly, the Valvetronic sensor seal). For now, remove the Valvetronic motor seal by undoing the two T30 screws. The Valvetronic sensor seal can then be pried out with a flat head screw driver.

Step 8: Installing the valve cover

The trick here is making sure you don't roll the valve cover gasket pushing the valve cover into place. It's also important to make sure the spark plug tube seals don't fall out. Putting the valve cover back in is more challenging than getting it out. Basically, I had to put the valve cover in at an angle towards the back passenger side of the engine to clear the e-box and windshield cowl. You need to have a steep angle to make sure the valve cover clears the eccentric shaft tower on the intake side of the engine. My hand is the only way I can really communicate this insertion strategy:

bmw-e90-engine-bay

Once the valve cover is in place, go around the perimeter and make sure the gasket is still in place. Now comes time to torque the valve cover bolts. BMW's TIS manual recommends 9Nm or torque on the valve cover bolts. I torqued the original bolts back down in a Z pattern to make sure the valve cover was torque evenly on the cylinder head. This was tough with the rear screws, but I did the best I could with the space I had. Once the valve cover bolts are torqued down, it's time to install the new spark plug tube sleeves. Line them up inside the spark plug tubes and snap them into place (they can only be installed one way). Now replace the Valvetronic motor seal. Simply put it into place (only fits in one way) and install the two T30 screws. At this point, it's also a good time to reinstall the Valvetronic motor. Put the motor in place and use the 4mm allen socket to spin the motor counterclockwise. You will notice the motor being pulled in. Once you feel tension, stop spinning the motor and reinstall the torx screws securing the motor to the valve cover. Torque to 10Nm. The Valvetronic sensor seal can basically be pushed into place. If you have a 32mm socket on hand, you can use this to gently tap it in until it bottoms out against the valve cover. In my case, I was just able to push it in with my thumbs.

Step 9: Put it all back together

At this point, you're basically done with all the hard stuff. Make sure you reconnect all electrical connectors, reinstall the ignition coils, ground straps, secondary air injection parts (if applicable). You should be left with an engine bay that looks like this:

bmw-e90-engine-bay

Now, reconnect the battery. If you have ISTA or INPA, now is a great time to reset the stop limits for the Valvetronic system. If you do not have ISTA or INPA, you can do this manually by turning the car on in accessory mode (position 2 no start) a few times. It will take a couple of days for the Valvetronic system to completely reset without a hard reset electronically, so you may notice some roughness when the engine idles.

And that's all there is to it! If this guide was helpful, let us know in the comments. If we missed anything, also let us know!

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