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BMW 3 Series: N42/N46 VANOS and timing chain tensioner failure (318i/318Ci)

N42/N46 VANOS and timing chain tensioner failure (318i/318Ci) is a common engine fault on the BMW 3 Series on the 1998–2006 cars, and we rate it major. Putting it right costs $900 to $3,200 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 88 documented faults on the BMW 3 Series.

Vehicle
BMW 3 Series
Engine
N42 / N46
Years
1998–2006
Fuel
petrol
System
Engine

This page covers the BMW 3 Series as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All BMW 3 Series faults88 documented faults on this model

What you are looking at

The front of a dual overhead camshaft engine with the timing cover removed, exposing the timing chain and sprockets.Example of the part — not this vehicle

The front of a twin-cam engine with the timing cover off — chain, sprockets and guides.

Logansenf · CC BY-SA 4.0 · Wikimedia Commons

What goes wrong

The N42 and N46 engines used in 318i and 318Ci models have a more complex dual-VANOS system with electric actuators and a timing chain that is known to stretch prematurely. The chain tensioners lose pressure at low oil levels or on cold starts, causing chain rattle and potential timing jump. Combined with N42/N46 VANOS electrical faults, these engines require more diligent maintenance than the M54. High oil consumption is also documented on the N46.

What you would notice

  • Loud rattling from engine on cold start, especially in winter
  • High oil consumption between services (over 1L per 3,000 km)
  • Rough idle with multiple misfires or cam fault codes
  • Loss of power with check engine light

How to check it

Where to look. Timing chain at front of engine; VANOS actuators on both inlet and exhaust camshafts

  1. Check oil level carefully — N46 engines consume oil and low levels accelerate chain tensioner and VANOS wear.

  2. Cold-start and listen for chain rattle in the first 10 seconds.

  3. Scan for cam timing, misfire, and VANOS fault codes.

  4. Check service history for oil change intervals (should be no more than 10,000 km).

  5. Ask about oil top-up frequency.

Parts involved: Timing chain.

What it costs to put right

$900 to $3,200 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

  • “How often does the car need an oil top-up between services?”
  • “Has the timing chain or tensioner ever been replaced?”
  • “Has it ever had a misfire or check engine light related to the N42/N46?”

Now check the BMW 3 Series you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.

BMW 3 Series buyer questions

Is n42/n46 vanos and timing chain tensioner failure (318i/318ci) serious on a BMW 3 Series?

We rate it major and common on the BMW 3 Series. The N42 and N46 engines used in 318i and 318Ci models have a more complex dual-VANOS system with electric actuators and a timing chain that is known to stretch prematurely. The chain tensioners lose pressure at low oil levels or on cold starts, causing chain rattle and potential timing jump. Combined with N42/N46 VANOS electrical faults, these engines require more diligent maintenance than the M54. High oil consumption is also documented on the N46.

How much does it cost to fix on a BMW 3 Series?

$900 to $3,200 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which BMW 3 Series years are affected?

Our research records this fault on the 1998–2006 BMW 3 Series. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.

How do I check for it before I buy?

Check oil level carefully — N46 engines consume oil and low levels accelerate chain tensioner and VANOS wear. Cold-start and listen for chain rattle in the first 10 seconds. Scan for cam timing, misfire, and VANOS fault codes. Check service history for oil change intervals (should be no more than 10,000 km). Ask about oil top-up frequency. Look here: Timing chain at front of engine; VANOS actuators on both inlet and exhaust camshafts