E46 Oil Filter Housing Gasket —
The oil leak BMW forgot to tell you about

Do an oil change at the same time — you're this deep anyway. Drain the oil first. Then remove the fan clutch (32mm, reverse thread — clockwise = loosen) and fan shroud. This gives you working room at the front of the engine where the oil filter housing sits.

Use a 36mm socket to unscrew the oil filter cap. The filter and cap come out together. Set them aside. You'll see the oil filter housing body still mounted to the engine with several bolts around its perimeter. This is what you need to remove.

The VANOS oil line connects to the side of the oil filter housing with a banjo bolt. Use a 17mm wrench to remove the banjo bolt. Have a rag ready — oil will seep out. Note there are two copper crush washers on the banjo bolt — one on each side. These are single-use and must be replaced.

Remove all the bolts holding the housing to the engine block — typically 5–6 bolts around the perimeter using a 10mm socket with an extension. The housing will pull straight off. Keep a rag under it as trapped oil will drain out. Take the housing to a clean work surface.

The old profile gasket sits in a groove in the housing. Use a pick tool to carefully remove it — it will be hard and shrunken. Clean both the housing mating surface and the engine block surface thoroughly with brake cleaner. Both surfaces must be completely oil-free and dry before installing the new gasket.

Look inside the housing where the non-return valve sits. You'll see a plastic valve with fins. Check the surrounding aluminum bore for a groove worn by the fins. If a shallow groove is present, push the valve in and rotate it 30–60 degrees so the fins land on fresh aluminum, not the groove. If the groove is deep enough that the valve falls back, replace the entire housing.

Press the new profile gasket firmly into the groove in the housing all the way around. Reinstall the housing on the engine, thread all bolts in by hand, then torque to 10 Nm in a star pattern. Reconnect the VANOS line with new crush washers — torque the banjo bolt to 25 Nm. Install a fresh oil filter and cap, torque the cap to 25 Nm.

Refill with fresh BMW LL-01 spec oil. Start the engine and let it idle. Watch the front of the engine where the housing is — it should be completely dry within 2–3 minutes of running. The oil pressure light should go out within 1–2 seconds on a warm restart. Check again after a 15 minute drive.

Before jacking the car up, tap out the staked portion of the hub nut with a punch and remove the dust cap. Use a 46mm socket and a long breaker bar or impact gun to break the hub nut loose while the wheel is still on the ground providing resistance. This nut is torqued to 290 Nm — it's extremely tight.

Jack the car and support on stands. Remove the wheel (17mm). Remove the two 16mm caliper bolts and hang the caliper with wire from the strut — never let it hang by the brake hose. Remove the rotor retaining screw (6mm hex) and slide the rotor off.

With the nut removed, the hub assembly should slide off the spindle. If it's stuck, reinstall 2–3 wheel bolts and use them as pull points — rock and pull the hub toward you. Alternatively, a slide hammer attached to the wheel bolt holes provides controlled pulling force. Never hammer on the spindle or hub face.

Sometimes when the hub pulls off, the inner bearing race stays behind on the spindle. This is common on high mileage or rusty cars. Use a thin two-jaw puller or carefully score the race with a Dremel cutting wheel (one light cut through the race) then pop it off with a screwdriver and hammer. Clean the spindle thoroughly with emery cloth once the race is off.

Clean the spindle surface with emery cloth until it's smooth. Apply a thin coat of anti-seize compound to the spindle to make future removal easier. Slide the new FAG hub assembly onto the spindle. Thread the new hub nut by hand as far as it will go — the nut will pull the hub onto the spindle as you torque it.

Torque the new hub nut to 290 Nm (214 ft-lbs). Once fully torqued, use a punch or chisel to stake the edge of the nut into the groove on the spindle — this locks the nut and prevents it from loosening. A staked hub nut is a safety feature. Do not skip this step.

Reinstall the rotor, thread in the retaining screw finger tight. Reinstall the caliper and torque the bolts to 81 Nm. Reinstall the wheel and torque in a star pattern to 120 Nm. Lower the car and take a progressive test drive — the humming noise should be gone immediately.

The cabin filter housing is located at the rear of the engine bay, up against the firewall near the windshield base. You'll see a plastic housing with three spring-loaded locking tabs. It's impossible to miss — it's the only thing back there with tabs on it.

Rotate each of the three tabs 90 degrees counter-clockwise to unlock them. Once all three are unlocked, lift the lid straight up and off. The lid separates from the housing cleanly — set it aside.

The filter slides straight up out of the housing. Pull it out and look at the dirty side. A brown or gray filter means it was overdue. A filter with visible debris or mold means your cabin air quality has been terrible for some time. Dispose of the old filter immediately — the debris will fall back into the housing if you shake it around.

The new filter has two plastic spikes/pins on one side. These go into the housing — they lock the filter in place. Slide the filter into the housing with the pins going in first. The filter should seat firmly with no gap around the edges. The airflow direction arrow on the filter should point toward the cabin.

Place the lid back on and twist each of the three tabs 90 degrees clockwise to lock. That's it. Close the hood. Turn on your HVAC on full blast for 30 seconds — you'll immediately notice improved airflow and no musty smell. You just saved yourself $80.

You cannot find a leak on a dirty engine. Get a can of engine degreaser, spray down the entire PS system — reservoir, hoses, pump, rack boots — and rinse clean. Let it dry completely. Now park over cardboard and drive the car for 15 minutes to warm everything up. Come back and look underneath for fresh fluid on the cardboard.

The PS reservoir has an internal filter that cannot be serviced — only the reservoir itself can be replaced. Look for hairline cracks in the reservoir body and weeping around the cap O-ring. The cap O-ring fails frequently on high mileage E46s. A wet or oily cap area means the O-ring needs replacement.

Two hoses connect to the bottom of the reservoir. These hose connections are a very common leak point — look for weeping or oil residue around the connection points. Squeeze the hoses at the clamps — any cracking or softness means replace the hose.

Get underneath and squeeze the rubber boots on both ends of the steering rack. If you hear or feel fluid sloshing inside the boot, the rack seals are leaking. This is a more serious repair — the rack itself needs rebuilding or replacement. Rackdoctor.net does E46 rack rebuilds for a fraction of a new rack cost.

Drop a few drops of PS fluid on white paper. ATF should be clear red or light amber — dark brown or black means severely degraded. CHF 11S should be clear green or light amber — dark or foamy means replace. Dark foamy fluid causes pump damage and rough steering feel. A fluid flush often resolves mild steering whine and heaviness.

Use a turkey baster or fluid syringe to remove as much old fluid from the reservoir as possible. The reservoir has a dipstick on the underside of the cap — note the MIN and MAX marks. Extract until near the minimum level. Refill with fresh fluid of the correct type to the MAX mark.

With the engine running, turn the steering wheel slowly from full left lock to full right lock five or six times. This pumps old fluid out of the lines and rack. Check the reservoir level and top off. Repeat until the fluid coming from the dipstick is clean and the correct color. This takes 1–2 liters of fresh fluid total.

Check the fluid level with the engine warm — there are two marks, one for cold and one for warm. Top off to the correct warm mark. Test drive and check for improved steering feel and reduced whine. If whining continues after a flush, the pump itself may be failing.

Take a clear photo of both belts showing exactly how they route around all pulleys. This takes 10 seconds and will save you from a frustrating puzzle when it's time to reinstall. Belt routing is not always obvious and the diagram in the repair manual is hard to read.

With the engine off, look closely at both belts. Run your finger along the inside (ribbed surface) — any cracking means replace immediately. Look at the back (smooth surface) for glazing or shiny spots — glazed belts slip and squeal. Check for fraying at the belt edges. Any one of these defects is reason to replace.

Use a 15mm socket on the AC tensioner bolt and push to release tension. The tensioner pivots on a bolt — pushing it compresses the spring and loosens the belt. Slip the belt off the AC compressor pulley first, then route it off the other pulleys. The AC belt is the shorter of the two.

The alternator tensioner is a separate unit — also 15mm. Release tension and slip the alternator belt off. Note the routing carefully before it comes all the way off. The alternator belt runs around the crankshaft pulley, water pump pulley, alternator, and tensioner.

With both belts off, the tensioner is now easily accessible. Remove the central bolt and pull the tensioner off. Compare with the new unit — if the spring in the old tensioner has any play or the pulley wobbles, you made the right call replacing it. A failed tensioner can throw a belt at speed.

Install the alternator belt first using your reference photo for routing. Route it around all pulleys except the tensioner pulley last. Use the 15mm to compress the tensioner while you seat the belt on the tensioner pulley. Release the tensioner — belt should be firm with no slack. Repeat for the AC belt.

Start the engine and listen for squealing. New belts sometimes squeal briefly for the first few starts as they seat in. Turn the AC on and off — if the AC belt squeals when the compressor kicks in, it may be slightly loose. Turn the steering wheel full lock — power steering should be smooth and quiet with the new alternator belt.