BMW N42

The BMW N42 is a straight-4 DOHC piston engine^[1] which replaced the M43 and was produced from 2001-2004.^[2]

Compared with its M43 predecessor, the N42 features a DOHC valvetrain, variable valve timing (called VANOS by BMW) and an aluminium engine block.^[3] It was the first BMW engine to feature variable valve lift (called valvetronic by BMW).^[4][5] The N42 serves as the basis for the smaller N40 engine (which does not have valvetronic).

The N42B18 won the 1.4-1.8 L category of the International Engine of the Year competition for 2001.^[6]

In 2004, the N42 was replaced by the N46 engine.

Models

N42B18

The N42B18 has a displacement of 1796 cc,^[1] uses Bosch DME ME9.2 fuel injection^[7] and has twin-balancing shafts.

The N42 has a few problems in service. The timing chain can stretch due to lightweight construction and damage/break the chain guides leading to possible engine damage. It is highly advisable to install the updated version of the timing chain tensioner (part number 11317567680). The updated version is slightly longer and stiffer. Valve guide seal wear is common on the N42 engine, leading to high oil consumption and oil smoke from the exhaust. To test whether the valve guide seals are worn out, let the engine idle for some minutes and then press the accelerator while in neutral. If the seals are worn, the car will smoke substantially. Oil consumption can also be caused by a clogged crank case valve or any of the related hoses. It is advisable to replace the crank case valve in time, preferable with the cold country version which has extra insulation. Oil leaks are common from the following areas: cam cover, oil filter housing, sump gasket, dipstick tube, brake vacuum pump, Vanos solenoids. Rattling Vanos units are due to either outright failure, or decreased oil supply due to clogged or faulty solenoids. Using the right oil, a maximum of 15.000km oil changes and avoiding short trips is a good idea to keep the N42 engine running well. The top end of the engine can suffer corrosion if the oil is not changed regularly and poor idling can be due to a worn Valvetronic eccentric shaft. The Valvetronic motor that operates the shaft can also fail although this can be due to either a faulty Valvetronic sensor of Valvetronic ECU.

Applications:

• 2001-2004 E46 316i and 316ti

N42B20

The N42B20 has a displacement of 1995 cc,^[1] uses Bosch DME ME9.2 fuel injection and has twin-balancing shafts.

The 2.0 version of the N42 suffers exactly the same faults in service as the 1.8.

Applications:

• 2001-2004 E46 318i/318Ci/318ti

See also

• List of BMW engines
• BMW M44

References