Bmw N55 Valve Cover Gasket Replacement – Stop Oil Leaks And Save
Replacing a leaking valve cover gasket on the BMW N55 engine is a critical maintenance task that prevents oil from damaging the alternator and drive belt. This guide provides a step-by-step walkthrough for DIYers to successfully seal their engine and avoid costly shop labor fees.
Seeing a puff of smoke from your hood or smelling burning oil through the vents is a rite of passage for most BMW owners. The N55 engine is a powerhouse, but its high operating temperatures eventually turn the rubber gaskets into brittle plastic.
Performing a bmw n55 valve cover gasket replacement yourself can save you upwards of $800 in labor costs while ensuring the job is done with precision. It is a labor-intensive process, but with the right tools and a bit of patience, any weekend mechanic can tackle it.
In this guide, we will walk through the entire procedure, from relieving fuel pressure to the final torque sequence. We will also discuss why you might want to replace the entire valve cover rather than just the gasket itself.
Why the N55 Valve Cover Gasket Fails So Often
The BMW N55 engine utilizes a plastic composite valve cover that sits directly above the turbocharger and exhaust manifold. This creates an environment of extreme heat cycling that few materials can withstand for more than 60,000 to 80,000 miles.
Over time, the rubber gasket loses its elasticity and begins to shrink, allowing oil to seep out. This oil typically drips onto the hot exhaust manifold, causing that signature burning smell and potential fire hazards.
Furthermore, the plastic valve cover itself is prone to hairline cracks. These cracks often occur in the internal channels of the Positive Crankcase Ventilation (PCV) system, which is integrated into the cover, leading to vacuum leaks and “whistling” noises.
Essential Tools and Parts for the Job
Before you begin, you need to gather specific tools. BMW uses External Torx (E-Torx) bolts extensively, and you cannot complete this job with standard metric sockets without risking stripped bolt heads.
- E-Torx socket set (specifically E10 and E12).
- 1/4-inch and 3/8-inch drive torque wrenches.
- 17mm flare nut wrench (for high-pressure fuel lines).
- Magnetic pick-up tool (for dropped bolts).
- Brake cleaner and lint-free shop towels.
Regarding parts, you have two choices: replacing only the gasket or replacing the entire valve cover assembly. Most experts recommend replacing the entire cover if your vehicle has over 100,000 miles to ensure the integrated PCV valve is fresh.
If you choose to only replace the gasket, ensure you buy a high-quality Viton or OEM-grade rubber seal. Cheap gaskets often fail within months, forcing you to repeat this entire multi-hour labor process.
Step-by-Step bmw n55 valve cover gasket replacement
Preparation is key to a successful bmw n55 valve cover gasket replacement. Start by parking the car on a level surface and allowing the engine to cool completely to avoid burns from the exhaust or fuel rail.
Step 1: Battery Disconnect and Cowl Removal
Always disconnect the negative battery terminal in the trunk before starting. You will be working near the alternator and fuel system, so eliminating the risk of electrical shorts is a mandatory safety step.
Remove the plastic cabin filter housing and the engine bay cowls. This requires removing several 10mm bolts and plastic clips to give you the necessary clearance to reach the rear bolts of the valve cover.
Step 2: Removing Strut Braces and Engine Cover
Many N55-equipped cars, like the 335i or 535i, have strut tower braces that block access. Remove these braces using an E18 or 13mm socket, depending on your specific chassis model.
Pull the plastic engine beauty cover straight up to release it from its rubber grommets. You should now have a clear view of the ignition coils and the complex wiring harness that sits atop the valve cover.
Step 3: Managing the Fuel System and Wiring
The N55 is a direct-injection engine, meaning the fuel lines are under high pressure. Carefully loosen the 17mm nuts on the metal fuel lines connecting the rail to the injectors, using a rag to catch any spray.
Unplug the ignition coils and the Valvetronic motor connector. Carefully move the wiring harness to the side; using bungee cords to hold the harness out of the way can make the rest of the job much easier.
Step 4: Valve Cover Removal
Loosen the perimeter bolts of the valve cover in a reverse-spiral pattern. Note that these bolts are usually captive, meaning they stay inside the plastic cover even when fully unscrewed from the cylinder head.
Gently pry the cover upward. If it feels stuck, double-check the very back corner near the firewall, as there is often a “hidden” bolt that is difficult to see but essential to remove.
Cleaning and Preparing the Mating Surface
Once the cover is off, you will see the camshafts and the cylinder head surface. It is vital that the aluminum mating surface is perfectly clean and dry before the new gasket is installed.
Use a microfiber cloth soaked in brake cleaner to wipe away all traces of old oil and debris. Do not use metal scrapers, as any gouge in the aluminum will create a permanent leak path that a new gasket cannot seal.
Check the spark plug wells for pooled oil. If oil has leaked into these tubes, use a vacuum or clean rags to soak it up before installing new spark plugs or reinserting the ignition coils.
Reinstallation and Torque Specifications
Properly seating the gasket is the most common point of failure for DIYers. Ensure the gasket is fully seated in the groove of the valve cover before you attempt to flip it over and place it on the engine.
The “Blind” Installation
As you lower the cover back onto the head, be extremely careful not to let the gasket fall out of its channel at the rear. Use your fingers to feel around the back of the engine to ensure the rubber is still in place.
If the gasket gets pinched during installation, it will leak immediately upon startup. Many technicians use a small amount of gasket tack or a tiny dab of RTV at the half-moon sections to keep the seal from shifting.
The Tightening Sequence
Tighten the bolts in a spiral pattern starting from the center and working your way out. This ensures even pressure across the plastic cover and prevents it from warping or cracking during the process.
The torque spec for N55 valve cover bolts is typically 8.5 Newton-meters (approx 75 inch-pounds). Do not over-tighten these bolts, as the plastic tabs on the cover are fragile and will snap under excessive force.
Common Pitfalls and Pro Tips
One of the biggest challenges during a bmw n55 valve cover gasket replacement is the PCV vent hose located at the back of the cover. This plastic hose becomes extremely brittle and almost always breaks during removal.
It is wise to order a replacement PCV vent hose (also known as the breather hose) before you start the job. Having this $30 part on hand will save you from being stranded with a vacuum leak after you finish the assembly.
Additionally, pay close attention to the Valvetronic eccentric shaft motor gasket. This is a separate, small gasket that often leaks oil directly into the motor’s electrical connector, which can lead to expensive sensor failures.
While You Are In There: Maintenance Synergies
Since you have removed the cowl, fuel lines, and coils, this is the perfect time to perform other “while you’re in there” maintenance. This saves you hours of redundant labor in the future.
- Spark Plugs: N55 engines are sensitive to spark plug gaps; replace them every 40,000 to 60,000 miles.
- Ignition Coils: If you have high mileage or experienced misfires, install a fresh set of Eldor or Bosch coils.
- Oil Housing Gasket: If you see oil near the front of the engine, the oil filter housing gasket is likely the culprit and is easier to access now.
By combining these tasks, you ensure the top end of your engine is sealed and tuned for another several years of high-performance driving. It turns a repair into a comprehensive reliability upgrade.
Frequently Asked Questions About BMW N55 Valve Cover Gasket Replacement
How long does this job typically take?
For a first-timer, expect the job to take between 4 and 6 hours. Experienced DIYers can often finish it in about 3 hours, depending on how much cleaning is required.
Should I replace the whole cover or just the gasket?
If your BMW has over 90,000 miles, replace the entire valve cover assembly. The integrated PCV valve eventually fails, and the plastic cover can warp, making a new gasket useless.
Can I use RTV silicone instead of a gasket?
No. You should never use RTV as a primary seal here. You may use a tiny drop of RTV at the “half-moon” corners of the head, but the main seal must be the rubber gasket itself.
What happens if I don’t replace a leaking gasket?
Oil will eventually saturate the serpentine belt, causing it to slip or snap. In some BMW models, a snapped belt can actually be sucked through the front main seal, destroying the engine.
Final Thoughts on Sealing Your N55
Tackling a bmw n55 valve cover gasket replacement is a rewarding project that every serious BMW owner should consider. It requires a methodical approach and the right tools, but the results are a cleaner engine bay and a more reliable vehicle.
Always double-check your torque settings and ensure no wires are pinched under the cover before you fire up the engine. Once finished, clean the engine block with a degreaser so you can easily spot any future leaks.
Stay patient, follow the steps carefully, and enjoy the peace of mind that comes with a leak-free BMW. Stay safe and keep your engine running strong!
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