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BMW N42B18 Engine (Design, Specs, Reliability)

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Last Updated on: 16th November 2023, 02:44 am

BMW N42B18 engines are in-line 4-cylinder engines with a DOHC system, they produce 116 hp and 175 nm of torque. The M43 series engines were the predecessors of this unit type.

The two overhead camshafts and the unique VANOS system are the N42B18’s standout features. This technique allowed for lower fuel use and less pollution from exhaust gases.

Valvetronic technology helps to improved power by optimising the cylinder filling with the mixture.

In this article, we’ll discuss the design, reliability and issues of the BMW N42B18 engine.

N42B18 engine


  • Production years: 2001-2004
  • Displacement: 1796 cc
  • Fuel system: injector
  • Power output: 116 hp @ 5500 rpm
  • Torque output: 175 nm @ 3750 rpm
  • Block: aluminum R4
  • Cylinder head: aluminum 16v
  • Cylinder bore: 84 mm
  • Piston stroke: 81 mm
  • Compression ratio: 10.5:1
  • Features: Valvetronic
  • Hydraulic lifters: yes
  • Timing drive: chain
  • Phase regulator: double VANOS
  • Turbocharging: no
  • Recommended engine oil: 5W-30
  • Engine oil capacity: 4.25 litres
  • Fuel type: Petrol
  • Euro standards: EURO 3
  • Fuel consumption, L/100 km (for 316i E46): city 9.9, highway 5.5, combined 7.1
  • Engine lifespan: ~250 000 km
  • Engine weight: 120 kg

Problems & Reliability

The N42B18 is inexpensive and effective, but it is also quite fragile and must be continually watched and is not as dependable as the M40-M43.

  • Overheating
  • Noise
  • Other issues

1. Overheating

The major cause is improper radiator cleaning, as well as a faulty thermostat, which only has to be replaced every 100 thousand kilometres.

This results in the failure of the valve stem seals. As a consequence, the unit uses an excessive amount of oil. As a result, you should constantly check the cooling system.

2. Noise

The chain tensioner must be totally replaced to correct the break. Its formal name is plus or minus 100 thousand kilometres.

You should also inspect the timing chain, which may extend and cause noise to rise.

3. Other Issues

You should also keep in mind that while replacing spark plugs, the coils of the BREMI ignition system often degrade. It’s preferable to convert the latter to EPA.

The N42’s engine appreciates excellent oils. It is preferable to use just the oil advised by the manufacturer.

The engine has a high heating temperature, and conserving oil usually necessitates an overhaul. It is not uncommon for the vanos to need to be replaced as well.


Tuning a N42B18 is a difficult and time-consuming task. There isn’t much on the market that can help you improve your HP.

The only method to boost engine power is to purchase a cold air intake system, a cat back performance exhaust system, and then continue with engine management tuning.

These adjustments will allow you to get an extra 10 HP.


BMW N42B18
  • Andy Lewin

    Andy Lewin is a senior mechanic, ASE qualified master technician, and an experienced automotive engineer. He's passionate about serving the automotive community with the highest-quality and trustworthy information on all things automotive. He loves to write about car repairs, maintenance, car modifications and tuning, faults, and much more.

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