How to Replace Valve Cover Gasket on BMW N52 - E90 DIY

I have done this job more times than I can count on E90 328i platforms and the procedure is well-understood. The N52 valve cover itself is a large plastic unit sitting on top of the engine, and while it looks intimidating because of all the wiring and vacuum lines around it, the actual removal is methodical and completely manageable for a home mechanic with basic tools and a few hours on a Saturday morning. The total DIY cost for the Elring gasket kit runs around $30 to $50, versus $300 to $500 at a dealer or independent shop.

There is one additional component I always replace at the same time - the VANOS solenoid O-rings. The VANOS system (BMW's variable valve timing) has two solenoids on the N52 that protrude through the valve cover. Their O-rings are made from the same material as the valve cover gasket, age at the same rate, and are responsible for a significant percentage of the oil leaks that get misdiagnosed as valve cover gasket failures. An Elring VANOS O-ring kit costs about $15 and takes an extra 20 minutes. Always do them together.

Diagnosing the N52 Valve Cover Gasket - What to Look For

Before you start pulling things apart, confirm the valve cover gasket is actually the source of your leak. On the N52, oil tends to accumulate at the back of the valve cover and run down toward the intake manifold or the firewall. A UV leak detection dye added to the oil and inspected with a UV flashlight is the most reliable diagnostic method - you will see bright yellow/green streaks leading back to the source.

A simpler field diagnosis - shine a flashlight into the spark plug tubes in the valve cover. The N52 has individual tubes for each spark plug and they should be clean and dry. If there is oil pooled in the bottom of any tube, the spark plug tube seals (which are part of the Elring kit) have failed. This oil contacts the coil packs, degrades their boots, and causes misfires. This is the most common collateral damage from a neglected valve cover gasket on the N52.

Also check the PCV (positive crankcase ventilation) system while you are in there. The N52 PCV is integrated into the valve cover and uses a check valve and oil separator. A failed PCV system increases crankcase pressure, which in turn accelerates valve cover gasket leaks. If the PCV check valve is hard or cracked, replace it as part of this job - it is inexpensive and accessible once the cover is off.

Tools and Parts Required for the N52 VCG Job

Parts you need - Elring complete valve cover gasket kit for N52 (this should include the main gasket, spark plug tube seals, and VANOS solenoid O-rings; double-check the kit contents), PCV check valve (optional but recommended at high mileage), new spark plug tube seals if not in kit, and fresh engine oil to top off after the job since you will lose a small amount during removal.

Tools - 8mm and 10mm sockets, T30 and T40 Torx bits, screwdrivers for hose clamps, needle-nose pliers for vacuum line clips, a torque wrench (critical for the correct torque sequence), a gasket scraper or plastic trim tool for cleaning the sealing surface, and clean shop rags. A small pick or hook tool is helpful for removing the old O-rings from the VANOS solenoids without scratching the seating surface.

Removing Components to Access the N52 Valve Cover

Begin with the engine cold or at least fully cooled. Remove the engine cover by pulling it straight up from its rubber grommets. Next, remove the intake hose from the airbox to the throttle body - it is secured with one large spring clamp and a smaller hose clamp. Unplug the MAF sensor connector and set the intake hose aside.

Now identify and label every connector, vacuum hose, and bracket attached to or routed across the valve cover. On the N52 E90, you have the VANOS solenoid connectors (two), the CPS (camshaft position sensor) connector, the ignition coil connectors (six - unplug and pull the coils straight out, they just press-fit into the tubes), and a series of vacuum lines and brackets that vary slightly by model year and equipment.

Take photos before disconnecting anything. I photograph from three angles - driver side, passenger side, and top-down. When you are tired and reassembling at 6pm, those photos save enormous amounts of frustration. Label vacuum hoses with masking tape and a marker if there are more than three or four of them.

Remove the ignition coils - unplug the connector, grasp the coil body firmly and pull straight up. They seat with a friction fit and should come out without excessive force. Set all six aside in order so you reinstall them in the same positions. Inspect the coil boots for oil contamination - if any coil has oil on its boot, clean it with brake cleaner before reinstalling.

Removing the N52 Valve Cover

With all connectors, vacuum lines, and ignition coils removed, locate all the valve cover bolts. On the N52, there are typically 20 to 24 bolts of varying lengths arranged around the perimeter of the cover. Use a 10mm socket (and in a few tight spots, a T30 Torx) to remove them all. Place them in a tray in order so you know which length goes back where - the N52 has bolts of at least two different lengths.

With all bolts removed, the valve cover should lift straight up. It may be stuck to the old gasket in spots - do not pry with a metal tool against the cover or block mating surface. Instead, give it a gentle tap with a rubber mallet around the perimeter. It will break free. Lift it straight up and be prepared for a small amount of oil to drip from the cover - have a rag ready.

Set the cover on a clean surface. Inspect the inside for sludge or debris. If you see heavy sludge buildup (thick brown or black deposits), that indicates infrequent oil changes and the engine may need a flush before the new gasket goes on. Do not seal in dirty oil with a fresh gasket.

Cleaning the Sealing Surfaces and Installing New Gasket

This step is where attention to detail separates a job that lasts 100,000 miles from one that leaks within 6 months. Use a plastic scraper to remove all old gasket material from both the cylinder head and the valve cover mating surfaces. Work carefully around the spark plug tube holes - any debris that falls into the engine is a problem.

Wipe both surfaces with brake cleaner on a clean rag until there is zero residue. Let the surfaces dry completely before installing the new gasket. The Elring gasket does not require additional sealant on most of its run, but on the N52 I apply a very small dab of Drei Bond 1209 (BMW's specified sealant) at the two corners where the head meets the timing chain cover - these are known leak points where a flat gasket cannot achieve perfect sealing geometry.

Install the new VANOS solenoid O-rings first - these go on before the cover because they sit in recesses in the cylinder head that become inaccessible once the cover is down. Use the pick tool to carefully remove the old O-rings, clean the grooves with brake cleaner, and press the new O-rings into place. A light smear of fresh oil on the new O-rings helps them seat and prevents tearing during installation.

Place the new gasket on the cylinder head. It should sit perfectly in the groove around the perimeter. Place the new spark plug tube seals in their positions. Lower the valve cover straight down onto the head, taking care not to disturb the gasket or tube seals during placement. Thread in all bolts finger-tight before torquing anything.

The Critical Torque Sequence for N52 Valve Cover Bolts

This is the part most DIYers rush and then wonder why their new gasket still leaks. The N52 valve cover bolts follow a three-stage torque sequence starting from the center and working outward in a cross pattern, similar to head bolt torque procedure.

Stage one - torque all bolts to 4 Nm, working from center outward. Stage two - increase all bolts to 6 Nm in the same sequence. Stage three - final torque to 8 Nm. Check the torque spec in the Elring kit instructions as it can vary slightly for specific model years. Do not skip stages or combine them.

After torquing, reinstall ignition coils, reconnect all electrical connectors and vacuum lines, reinstall the intake hose, and reinstall the engine cover. Add a quart of fresh oil to compensate for any lost during the job, then start the engine and let it idle for 10 minutes while inspecting for leaks.

Follow-Up Maintenance After N52 VCG Replacement

With the valve cover off, you had a prime opportunity to inspect many components that are normally hidden. If you noticed anything concerning - cracked vacuum hoses, corroded connectors, or a PCV check valve that was hard as a rock - address those items now rather than scheduling another visit to the engine bay in a few months.

Monitor the spark plug tubes for oil over the next 1,000 miles. Pop the ignition coils out and check with a flashlight. Dry tubes mean the job was a success. Any oil reappearing in the tubes means either the tube seals were not fully seated or there is another leak source above the valve cover area.

For all engine maintenance resources on the N52 and related platforms, visit /engine. For cooling system maintenance that pairs well with this job, see /cooling. Related reading: /articles/bmw-n55-common-problems covers similar failure patterns on the turbocharged successor. And if you are considering upgrades after sorting the basics, see /engine/cold-air-intakes for N52 intake options.

N52 PCV System Inspection - Do Not Skip This Step

The N52 positive crankcase ventilation system is built directly into the valve cover and is inaccessible during normal maintenance without removing the cover. With the cover off during the gasket job, you have a rare opportunity to inspect the PCV components directly. The main check valve is a rubber diaphragm inside the PCV port on the underside of the cover. Press it with your finger - it should offer firm resistance and spring back immediately. If it is soft, collapsed, or cracked, it has failed and needs replacement.

A failed PCV check valve allows elevated crankcase pressure to build inside the engine. This pressure pushes against every oil seal and gasket simultaneously, accelerating VCG leaks significantly. On high-mileage N52 engines where the valve cover gasket has leaked twice or more, a failed PCV is often the true underlying cause. Replacing the gasket without addressing the PCV sets you up for a repeat failure within 30,000 miles - an outcome I have seen many times on cars that came back after a previous shop replaced the VCG but left the PCV unchecked.

PCV check valves for the N52 cost $10 to $20 and press into the port in the underside of the valve cover. Replace it as standard practice on any valve cover with more than 80,000 miles. While the cover is on the bench, also clean the oil separator mesh inside the PCV section using brake cleaner and compressed air. Years of blow-by deposits clog this mesh and further elevate crankcase pressure. Two minutes of cleaning on the bench meaningfully improves the long-term durability of the new gasket installation.

Additional maintenance resources: /engine, /cooling, /articles/what-bmws-have-the-b58, /engine/cold-air-intakes.