This article gives detailed instructions on replacing the valve cover gasket in a BMW with the N55 turbocharged 6 cylinder engine. Even though we used a 2011 335i to perform this repair, this article can be applied to any BMW vehicle with the turbocharged N55 engine including 1,2,3,4,5,6,7,X1,X3,X4,X5 and X6 models with minor modifications to the repair steps.
A BMW N55 valve cover gasket replacement will help cure the infamous oil leaks dripping on your turbocharger and exhaust pipes.
One of the more irritating issues plaguing BMW owners with the N55 turbocharged six cylinder engine are valve cover gasket oil leaks, especially around the exhaust manifold and the rear of the cylinder head. Although these leaks do not present an immediate danger, they do need to be ultimately fixed to keep burnt oil smoke from billowing from the engine compartment and into the interior of the vehicle.
A BMW N55 valve cover gasket seals the top of the cylinder head, preventing the oil that is being agitated by the cam shafts, valves and timing chain from escaping the engine. The valve cover gasket actually consists of four parts; a perimeter gasket that seals the outside edge of the cover and three interior gaskets that seal the spark plug wells. A BMW N55 valve cover replacement requires removing the cover and replacing all four gaskets.
The BMW N55 engine generates a tremendous amount of heat creating a brutal environment inside the engine compartment. These conditions play havoc on gaskets and seals, especially the valve cover which is situated in close proximity to the extremely hot turbocharger. As the valve cover gasket becomes brittle from heat and age it cracks, allowing oil from the cylinder head to slowly seep out around its edges. If the oil leak is on the right side or rear of the valve cover it will drip on the turbocharger, exhaust pipe or catalytic converter creating a burnt oil smell and blue smoke to emanate from under the hood. Often the leaks are very hard to visually observe, even with the vehicle up on a lift. Since the oil is usually instantly vaporized by the intense heat of the turbocharger and upper exhaust pipe, the only indication there is a leak is often just a plume of smoke.
A BMW N55 valve cover gasket replacement is actually not a difficult repair and should not intimidate the home mechanic with average skills. In fact the most time consuming part of the repair is clearing out the myriad of engine components that block access to the cover. Be sure to take your time while removing the cover – label all of the connections with high visibility tape to aid during reassembly.
We have included a handy checklist at the end of this article to help with reassembly.
1. Valve cover gasket (required) – Always use a high quality gasket in you N55 turbocharged engine. We give you several great options based on your budget and brand preference.
2. Crankcase vent hose (optional) – One of the most damaged parts when performing a BMW N55 valve cover gasket replacement is the crankcase vent hose. As this part ages it becomes extremely brittle and usually snaps in half during disassembly. Save time and avoid aggravation by ordering a new vent hose before starting the repair.
2. Valve cover (optional) – There is unfortunately a chance that the actual valve cover on your N55 engine is cracked causing an oil leak. The N55 valve cover is made of plastic and is susceptible to the same punishing heat conditions as the other parts in the engine compartment. If you determine that your cover is cracked, order from one of these OE quality replacements.
As previously discussed, the most time consuming part of removing the valve cover is clearing out the components around it. Take your time when disassembling the engine – we always use a high visibility masking tape to mark our connections so we don’t forget them during reassembly.
- Begin by disconnecting the negative battery cable from its terminal. Since you will be disconnecting sensitive electronics while performing this repair, ALWAYS disconnect the battery in your vehicle to avoid catastrophic damage to your vehicle’s electrical system.
- Remove the engine cover by pulling on it until it releases from its rubber mounting grommets.
- Remove the upper cabin air filter housing. It is held in place with six screws.
- Remove the cabin filter (microfilter).
- Unsnap and remove the left and right covers.
- Disconnect the hood switch on the left side of the lower cabin filter housing.
- Turn the automatic recirculated air sensor counterclockwise and pull it free from the right lower cabin filter housing.
- Using a body panel tool, remove the two plastic rivets anchoring the lower cabin filter housing to the body of the car. Remove the housing from the vehicle.
- Unplug the mass air flow (MAF) sensor.
- Use a flat blade screwdriver to loosen the hose clamp connecting the intake muffler lid to the upper intake air duct.
- Unclip the intake muffler lid and remove from the engine compartment.
- Use a 10mm socket wrench to remove the bolt anchoring the upper intake air duct to the valve cover.
- Next, unsnap the crankcase vent hose. Be very careful…the hose gets extremely brittle with age and is infamous for snapping off when being removed. Please see our parts list if you break yours. Use a flat blade screwdriver to CAREFULLY release the four plastic snaps (don’t forget the one underneath the hose). Pull the crankcase vent hose free from the valve cover.
- Disconnect the crankcase vent sensor from the upper intake air duct.
- Use a T27 torx bit to loosen the upper intake air duct from the lower turbocharger intake duct. Remove the upper air intake air duct from the vehicle. We strongly recommend covering the opening to the lower intake duct with tape to seal it off – this will prevent objects from inadvertently dropping in the pipe which could get caught in the turbocharger assembly.
- Disconnect the vacuum pump pipe from the valve cover by pinching in the sides of the fitting until it releases.
- Unplug the Valvetronic actuator on the top of the valve cover.
- Using an E14 external torx socket, remove the right strut brace bolt from the vehicle. Carefully rotate the strut brace out of the work area and secure with a bungee cord.
- Remove the cap from the positive battery terminal. Use a 13mm socket wrench to remove the nut securing the positive cable to the terminal. Move the cable out of the work area.
- Unplug the pneumatic wastegate actuator (located on the lower right side of the valve cover on the heat shield) the by pinching the metal release clip and pulling it free.
- Unplug the two vacuum lines from the side of the valve cover. Make sure to label them with high visibility tape so you don’t forget them during reassembly.
- Unplug the two oxygen sensor cables and stow them safely out of the way. Make sure to label at least one of them so you don’t get them mixed up during reassembly.
- Remove the left and right lock levers from the E-box. Slide the front and rear lock levers to the “unlock” position and remove the lid from the E-box.
- Pull the two wiring harnesses loose from the E-box and carefully bungee cord them out of the way off the work area.
- Unsnap the plastic retaining clip on the top of the six ignition coils and pull the plugs free.
- Using an 8mm socket wrench, remove the three grounding wires from the cylinder head.
- It is critical in this step to use patience. Use a small flat blade screwdriver to release the fuel injector plugs as shown below. DO NOT force the plug out of the injector by pulling on it. Use the screwdriver to release the plug until it easily pulls free.
- Unsnap the ignition coil wiring harness from the side of the valve cover and move out of the work area.
- Using a 14mm open end wrench, remove the six fuel lines from the top of the valve cover. Even though the amount of fuel in the lines is negligible, it is good practice to have a rag ready to soak up and gasoline.
- The valve cover is now clear of all connections and can be removed from the cylinder head.
The BMW N55 valve cover is held in place with 16 perimeter and 10 interior steel mounting bolts. Since the mounting bolts are steel and not aluminum, they typically do not need to be replaced when performing a BMW N55 valve cover gasket replacement. It is very important to note that the valve cover on an N55 engine is very easy to remove after all of its mounting bolts are loosened – if you cannot lift up on the valve cover after loosening the bolts you have most likely missed one. Usually mechanics forget the mounting bolt hidden behind the steel absorber (see step 1 below).
- Using a T20 torx bit, remove the steel absorber from the top of the valve cover. It is located on the middle/left side of the cover next to the fuel rail. This step is often overlooked by mechanics – it is important since there is a valve cover mounting bolt hidden below the absorber that must be removed.
- Using an E10 external torx socket loosen the 16 perimeter valve cover mounting bolts. Note that the bolts have steel collars on them that are pressed into the valve cover…they just need to be loosened until they are free of the cylinder head (you do not need to pull the collars out).
- The three mounting bolts on the rear of the valve cover are often a challenge to remove – exercise patience when dealing with them. As shown in the following images, we find the best way to loosen them is with a 1/4″ ratchet with an extension and a 3/8″ adapter from the torx socket. The 1/4″ ratchet gives the necessary clearance to reach the bolts heads.
- Next, loosen the ten interior valve cover bolts.
- The valve cover is now loose from the cylinder head and can be removed. Remove the valve cover by lifting the rear first – once the rear is raised above the cylinder head, the valve cover can be easily removed from the engine compartment. The valve cover should easily lift off of the cylinder head…if it doesn’t then you have missed a bolt.
- You can see from the following photos that we had a leak on the right rear side of the cover. Closer inspection shows where it was dripping on the catalytic converter, causing smoke to emanate from the engine compartment and into the cabin of the vehicle.
It is very important that the new valve cover gaskets are installed with an adhesive. Not using an adhesive between the gaskets and the valve cover will cause them to fall out and become damaged during installation. There are many theories scattered across online forums as to what is the best type of adhesive to use for this procedure; we have always used a general purpose spray adhesive like Permatex (see our supplies list) and it works great.
- Lay the valve cover on a work bench and thoroughly inspect it for cracks.
- Remove the old gaskets.
- Using a mild cleaner like Goof Off Power Cleaner and Degreaser, clean the valve cover gasket mounting surfaces. Use a plastic scraper to remove any old adhesives. Using compressed air, thoroughly blow out the valve cover – you want the gasket mounting surfaces to be thoroughly clean with no residue.
- Using the mild cleaner, thoroughly clean the cylinder head. Make sure to remove any oil residue and old adhesive. Clean any oil that has seeped onto the side of the engine, including patches of burnt oil. This will prevent the engine from smoking after completing this repair.
- Lay out your new perimeter gasket and have it lined up and ready for installation. The “round” circles line up with the bolt holes on the left side of the valve cover as shown below.
- Using a good spray adhesive like Permatex, spray a small section of the valve cover groove. IMMEDIATELY put the gasket in the groove while the adhesive is wet. DO NOT wait until the adhesive gets “tacky” before installing the gasket…it will only cause a mess and the gasket will not stick to the cover.
- Continue to spray small sections and install the gasket. Repeat with the three interior spark plug well gaskets.
- When you are finished, make sure the gaskets are firmly pressed in. Let the gaskets sit for approximately 30 minutes before installing the valve cover. This will give the adhesive time to set up.
Final reassembly is very straightforward…it is just the above steps in reverse. Take your time when installing the valve cover back in the vehicle. Move slowly and avoid getting frustrated if the cover will not immediately fit into place – sometimes it takes a a few “micro-adjustments” until the cover falls into position on the cylinder head. Trying to force the valve cover into place will only end up damaging the gasket or cracking the cover.
Once you have the valve cover in place, it is recommended that you use a “crisscross” pattern to torque the mounting bolts working from the interior of the valve cover towards the outside edges. The following is a handy bolt torque pattern diagram if you don’t already have your own system:
We have provided the following reassembly checklist with torque values for your convenience.
BMW N55 Valve Cover Gasket Reassembly Checklist
- Reinstall the valve cover and torque the mounting bolts to 10.5 Nm (8 ft-lb).
- Replace the steel absorber.
- Replace the fuel lines. Use a 14mm crow’s foot to torque the fuel line mounting nuts to 23 Nm (17 ft-lb).
- Snap the ignition coil wiring harness back into place on the right side of the valve cover.
- Plug the six fuel injectors back in.
- Reattach the three grounding wires to the cylinder head.
- Plug the six ignition coils back in.
- Reinstall the wiring harnesses back into the E-box. Replace the E-box lid.
- Reattach the two oxygen sensor connections.
- Reattach the two vacuum lines to the right side of the valve cover.
- Reinstall the plug back into the pneumatic waste gate actuator.
- Reattach the positive battery cable to the battery terminal. Torque the cable’s mounting nut to 25 Nm (18 ft-lb). Replace the plastic cap back on the terminal.
- Swivel the right strut brace back into position. Install its mounting bolt and torque to 43 Nm (31.5 ft-lb).
- Plug the Valvetronic actuator back in on top of the valve cover.
- Reconnect the vacuum pump pipe to the valve cover.
- Reinstall the upper air intake duct onto the lower duct. Tighten the T27 torx screw that connects them together.
- Plug the crankcase vent sensor back in.
- Reattach the crankcase vent hose to the valve cover.
- Reinstall the 10mm bolt securing the upper air intake duct to the valve cover.
- Reinstall the intake muffler lid. Tighten the hose clamp connecting it to the upper air intake duct.
- Reconnect the mass air flow (MAF) sensor.
- Reinstall the lower cabin filter housing.
- Reinstall the automatic recirculated air sensor.
- Plug the hood switch back in.
- Replace the left and right equipment covers.
- Replace the cabin filter and reattach its lid.
- Reinstall the engine cover.
- Reconnect the battery.