The BMW 318i in the fourth 3 Series generation (E46, built 1997–2006) was built with 2 different engines over its life: the M43B19 (118 hp, 1998–2002) and the N42B20 (143 hp, 2001–2004).
This guide tells you which engine your 318i has, what goes wrong with it, what a replacement costs from our stock and what else to plan for when you fit one.
- Generation: fourth 3 Series, 1997–2006
- Body styles: E46 (saloon, Touring, coupé, convertible, Compact)
- Engines: M43B19, N42B20
- Output: 118 hp and 143 hp
- Replacement engines in stock: ask the desk for the next arrival
Which engine is in your 318i?
| Engine code | Built | Power | Torque | Type |
|---|---|---|---|---|
| M43B19 | 1998–2002 | 118 hp | 180 Nm | 1.9 L petrol inline-4, naturally aspirated |
| N42B20 | 2001–2004 | 143 hp | 200 Nm | 2.0 L petrol inline-4, naturally aspirated |
M43B19 in the 318i
The M43B19 was used in the E46 318i, built 1998–2002. It is a 1.9 L naturally aspirated petrol inline-4 with 118 hp and 180 Nm. Compared with the N42B20 (143 hp), it is the mildest.
Reading the code: M marks an M-series code, the naming BMW used for its engine families up to the early 2000s; 43 is the family number; B stands for petrol (from the German Benzin); 19 is the capacity in decilitres, so 1.9 litres.
N42B20 in the 318i
The N42B20 was used in the E46 318i, built 2001–2004. It is a 2.0 L naturally aspirated petrol inline-4 with 143 hp and 200 Nm. Compared with the M43B19 (118 hp), it is the strongest.
Reading the code: N marks an N-series code, the generation of BMW engines introduced from 2001; 42 is the family number; B stands for petrol (from the German Benzin); 20 is the capacity in decilitres, so 2.0 litres.
318i engines by model year
| Model year | Engine |
|---|---|
| 1998 | M43B19 (118 hp) |
| 1999 | M43B19 (118 hp) |
| 2000 | M43B19 (118 hp) |
| 2001 | M43B19 (118 hp), N42B20 (143 hp) |
| 2002 | M43B19 (118 hp), N42B20 (143 hp) |
| 2003 | N42B20 (143 hp) |
| 2004 | N42B20 (143 hp) |
The engine changed 2 times during the E46 run, in 2001 and 2003. Changes usually come with BMW's mid-life update (LCI) or a new emissions standard, so a car registered early in a year can still have the older engine. The VIN settles it.
Other cars with the same engine as the 318i
A replacement engine does not have to come from another 318i. These models left the factory with the same engine code, so a unit from any of them is a candidate donor once the sump, mounts and ancillaries are matched to your car.
M43B19: BMW E46 316i.
How to confirm your engine code
Because the 318i used more than one engine, the badge alone does not tell you which one your car has. The build date is the first clue; the VIN is the proof. Send us the last seven characters of the VIN and we read the engine code from BMW's records, or look for the code stamped on the block. How to find your BMW engine code.
Known 318i engine problems
M43B19 (M43 family)
The M43B19 in the 318i shares the known weak points of the M43 family. Full M43 guide.
| Known fault | What to check |
|---|---|
| Timing chain guide rail | Remove the valve cover and inspect the top of the guide; replace it when fitting any used M43. |
| Valve cover gasket leaks | Look for burnt oil on the exhaust side. |
| Ticking hydraulic lifters | Listen after the engine has warmed; noise that stays is a lifter problem. |
| Engine mounts and vibration | Check mounts for split rubber when the engine is in the car. |
Timing chain guide rail. The M43's plastic guide rail can crack and break, which lets the chain slap and in the worst case jump. It is the single most important check on this engine.
Valve cover gasket leaks. The gasket hardens and oil seeps onto the exhaust manifold.
Ticking hydraulic lifters. Lifters tick after a cold start on old oil.
Engine mounts and vibration. Four-cylinder vibration finishes engine mounts, making the car shake at idle.
N42B20 (N42 and N46 family)
The N42B20 in the 318i shares the known weak points of the N42 and N46 family. Full N42 and N46 guide.
| Known fault | What to check |
|---|---|
| Oil consumption | Ask for consumption figures and check the spark plugs for oil fouling. |
| Timing chain stretch | Listen for a rattle on a cold start and check the camshaft timing values. |
| Valvetronic motor and eccentric shaft sensor | Check for Valvetronic fault codes. |
| Vacuum pump and oil leaks | Look at the back of the head. |
| Crankcase ventilation | Check for a whistle at idle. |
Oil consumption. Valve stem seals and piston rings let oil through; consumption above one litre per 1,000 km is not unusual on neglected engines.
Timing chain stretch. The N46 chain and tensioner wear, causing rattle and timing faults.
Valvetronic motor and eccentric shaft sensor. Both can fail and leave the engine in limp mode.
Vacuum pump and oil leaks. The vacuum pump seal and the valve cover gasket leak oil.
Crankcase ventilation. The CCV diaphragm splits, causing lean codes and a whistle.
Symptoms to watch for on the 318i
Rattle for a few seconds after a cold start. The classic sign of a weak timing chain tensioner or stretched chain. It must be checked quickly: a chain that jumps a tooth can bend valves.
Poor low-down torque and uneven idle. VANOS seals or solenoids. The engine may run well at high revs but feel flat and lumpy at low speed.
Limp mode with a Valvetronic fault. The Valvetronic motor, its eccentric shaft sensor or the wiring. The engine runs on a reduced throttle until it is repaired.
Looking after the 318i engine
M43 engines
- Oil: 5W-40 or 10W-40 synthetic, about 4.25 litres with filter.
- Service interval: Oil every 10,000 to 15,000 km; inspect the chain guide whenever the valve cover is removed.
- Timing drive: Single-row timing chain with a plastic guide rail and hydraulic tensioner.
- Workshop notes: Replace the guide rail, tensioner and valve cover gasket before fitting a used M43. It is a small job with the engine out.
N42 and N46 engines
- Oil: 5W-30 BMW Longlife-01 or Longlife-04, about 4.25 litres.
- Service interval: Oil every 15,000 km; shorten to 10,000 km to protect the chain.
- Timing drive: Timing chain at the front with balance shafts.
- Workshop notes: Replace the timing chain, tensioner and valve stem seals when fitting a high-mileage used N46.
Buying a used engine for the 318i: checklist
- Confirm the exact engine code. Read the code stamped on the block and compare it with the code for your car. Send us the last seven characters of the VIN and we confirm the match before anything is paid.
- Photographs from every side. Good suppliers photograph the actual engine you will receive. Look for the block stamp, the sump, the timing cover and any broken brackets or connectors in the pictures.
- Gearbox and flywheel match. Manual and automatic engines differ at the flywheel or flexplate, and sometimes at the crankshaft spigot. Make sure the engine you buy matches your gearbox or that you transfer the right parts.
- Warranty terms in writing. Read what the warranty covers, how long it runs and what fitting conditions apply. Most warranties require a qualified workshop, new fluids and filters, and replacement of the cooling parts that caused the original failure.
- Look at the oil and coolant. Clean oil without metal particles and coolant without oil are good signs. Milky oil, oily coolant or a burnt smell mean the engine needs further checks before it is fitted.
- Timing chain noise. Listen for a rattle at the front of the engine for the first seconds after a cold start. On an engine that cannot be run, look at the chain guides through the oil filler or with the valve cover off.
- VANOS operation. Rough idle, a rattle from the front of the head and a loss of torque at low revs point to VANOS seals or solenoids. These are serviceable parts and are easier to renew with the engine out.
- Double VANOS units and solenoids. Ask for the adaptation values or fault history if the engine was running. Solenoids are inexpensive and are often replaced as a matter of course on a used engine.
- Valvetronic motor and eccentric shaft sensor. The Valvetronic motor and its sensor cause limp-mode faults when they fail. Inspect the connector and the seal around the motor for oil.
BMW 318i replacement engine cost
We do not have a 318i engine on the shelf at the moment. Send us your VIN or the code you need and the desk will tell you when the next unit arrives and what it will cost.
On top of the engine, budget for the workshop's labour and the parts that are best replaced while the engine is out: engine mounts, the rear main seal, cooling parts, a clutch or converter seal, fluids and filters.
Will it fit my 318i?
Will the M43B19 fit my BMW E46 318i?
The M43B19 is the original engine for the BMW E46 318i, which makes it the straightforward choice. The fourth 3 Series was built 1997–2006, and the M43B19 was produced 1998–2002, so check that your car's build date falls inside that window. Confirm the drive type (rear-drive or xDrive), the gearbox (manual or automatic) and the emissions standard, because these can change the sump, the flywheel and the software. Send us the VIN and we check all of it for you.
How much is a replacement engine for a BMW E46 318i?
We do not have an M43B19 on the shelf for the E46 318i at the moment. Units arrive regularly; send us your VIN and we will tell you when the next one is ready and what it will cost, including delivery.
Will the N42B20 fit my BMW E46 318i?
The N42B20 is the original engine for the BMW E46 318i, which makes it the straightforward choice. The fourth 3 Series was built 1997–2006, and the N42B20 was produced 2001–2004, so check that your car's build date falls inside that window. Confirm the drive type (rear-drive or xDrive), the gearbox (manual or automatic) and the emissions standard, because these can change the sump, the flywheel and the software. Send us the VIN and we check all of it for you.
How much is a replacement engine for a BMW E46 318i?
We do not have an N42B20 on the shelf for the E46 318i at the moment. Units arrive regularly; send us your VIN and we will tell you when the next one is ready and what it will cost, including delivery.
Engine swaps and upgrades for the 318i
These engines were fitted to other versions of the E46 at the factory, which makes them the most practical upgrades: the body was designed around them and many parts are shared.
| Engine | Factory model | Power | Gain |
|---|---|---|---|
| M47TUD20 | E46 320d | 150 hp | +7 hp |
| M57D25 | E46 325d | 163 hp | +20 hp |
| M52B25 | E46 323i | 170 hp | +27 hp |
| M54B22 | E46 320i | 170 hp | +27 hp |
| M57D30 | E46 330d | 184 hp | +41 hp |
Can I fit the M47TUD20 in my 318i?
It is a full conversion: the M47TUD20 runs on diesel and the N42B20 on petrol, so the fuel system, wiring, engine control unit, instrument coding and usually the gearbox change too. The gain is 7 hp and 130 Nm. In Germany and most of Europe an engine swap must be inspected and registered.
Can I fit the M57D25 in my 318i?
It is a full conversion: the M57D25 runs on diesel and the N42B20 on petrol, so the fuel system, wiring, engine control unit, instrument coding and usually the gearbox change too. The gain is 20 hp and 150 Nm. In Germany and most of Europe an engine swap must be inspected and registered.
Can I fit the M52B25 in my 318i?
It is a conversion rather than a replacement: the M52B25 is an inline-6 and your N42B20 an inline-4, so mounts, sump, cooling, exhaust, wiring and the engine control unit all change. The gain is 27 hp and 45 Nm. In Germany and most of Europe an engine swap must be inspected and registered.
Fitting a replacement engine in the 318i
- Inspect or replace the timing chain parts. Look at the guides and tensioner. On high-mileage engines, replacing them now costs far less than doing it later.
- Reset VANOS adaptations. Clear the VANOS adaptations so the ECU learns the camshaft positions of the new engine.
- Teach the Valvetronic limit stops. Run the Valvetronic learning routine so the ECU knows the eccentric shaft limits.
- Fill with the right oil and prime it. Fill with new oil of the correct specification and a new filter. Crank with the fuel and ignition disabled until oil pressure builds.
- Coding and adaptations. On modern BMWs, the engine ECU must be matched to the car's immobiliser (CAS, FEM or BDC). Reset adaptations, register the battery and clear faults with diagnostic software.
- First start and leak check. Start the engine, let it idle and watch oil pressure, temperature and fault codes. Check for leaks and bleed the cooling system.
- First 1,000 km. Drive gently for the first few hundred kilometres, vary the engine speed and avoid full load. Change the oil and filter after about 1,000 km to remove any assembly debris.
The full fitting and first-start procedure.
318i engine questions
Will the N46B20 engine fit my BMW E46 318i?
Yes, if your BMW E46 318i was built with the N46B20. BMW used this 2.0 liter (1,995 cc) petrol engine with 110 kW (150 HP) in the E46 318i from about 2004 to 2012.
Some E46 318i cars were built with a different engine: the M43B18. These look alike from the outside, so check the code on your engine or send us your VIN.
Also tell us if your E46 has a manual or an automatic gearbox. The flywheel or the flex plate and some sensors depend on it.
Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.
See all N46 Engines · Search N46B20 in the shop
Delivery, warranty and payment
Every 318i engine we sell is drained, sealed at each opening, strapped to a heat-treated pallet and shrink-wrapped before it leaves Hamburg. You receive photographs of the packed engine and a tracking number.
Delivery is door to door and included in the price. Most European addresses receive the engine within five to ten working days; Germany and its neighbours are usually faster.
Every engine carries a 12-month warranty on eligible internal failure when a qualified workshop fits it with new fluids and filters. Payment is by card, bank transfer or crypto; your invoice is emailed as soon as you order.
All E46 engines · M43 engine guide · N42 and N46 engine guide · BMW 318i engines for sale · Send us your VIN
