8 CommonBMW N40 Engine Problems (E46 316i)

If you live in Europe, chances are a BMW E46 3 Series is a good contender for your first car or your daily beater! We already wrote an entire overview of the problems of the BMW E46 3 Series.

And you know what, it’s an amazing car and one of the rare BMW models that still look good today. If you’re in the market for an E46 316i, you came to the right place.

Doing your own research is always important before you decide to purchase a car with a certain engine. Not all engines are the same, some of them are more problematic, while some of them are not that prone to failures. So, this is why we are going to try to help you out and dissect every common problem with the N40.

First, we are going to cover the engine specs of the BMW N40, then we are going to discuss the BMW N40 engine problems, as well as the applications. So, let’s dive into the article.

Basic BMW N40 Engine Specs

The BMW N40 engine is an engine that was manufactured by BMW between 2001 and 2005. It was a short-lived engine that was included in only the BMW E46 platform.

Nevertheless, the N40 is an inline-4 engine that is naturally aspirated. It has a total displacement of 1.6 L.

The engine has a cylinder bore of 84 mm and a piston stroke of 72 mm. Both the block, as well as the cylinder head are made of aluminum.

When it comes to the cylinder head, it is worth noting that this engine implements double overhead camshaft (DOHC) layout with variable valve timing (VANOS),

This engine was based on the notorious N42 engine. The N40 is basically the same as the N42. It has the same crankcase, bore size, and the same pistons. But the only thing that it doesn’t have is the notorious Valvetronic (variable valve lift). This makes it a better option compared to the N42.

Another major difference between the N42 and the N40 is that the N40 has a shorter stroke, which results in a reduction in displacement. The N40 has 200cc less displacement, which makes it a bit underpowered.

There was only one spec of this N40 engine, this was the N40B16. This engine produces 85 kW (114hp) @ 6,100 rpm and 150 N-m (111 lb-ft) @ 4,300 rpm.

As you can tell, this engine is more about fuel economy rather than performance.

Common BMW N40 Engine Problems

Now let’s briefly list the common BMW N40 engine problems and see what troubles this engine the most.

Common BMW N40 engine problems include:

  • Timing Chain Tensioner Failure
  • VANOS Solenoid Failures
  • VANOS Solenoid Seal Leaks
  • Ignition Coil & Spark Plug Failure
  • PCV Valve Failure
  • Prone To Overheat & Consume Oil
  • Oil Leaks
  • Coolant Leaks

Since we listed the common BMW N40 engine problems, let’s move on and learn more about each of these problems in depth. How they occur, the symptoms, and what you can do about it.

Timing Chain Tensioner Failure

The first and most serious problem with this engine is the timing chain tensioner failure. And this problem happens very often on these engines, including the N42 since they are genuinely the same engine under the skin.

There is a tensioner bolt that tends to fail and cause all sorts of issues. In the worst case, the chain will jump and ruin the engine.

In 2003 BMW released an upgraded tensioner bolt for this engine that sorted out the issue.

What is bad though is that if the engine was produced pre-2003 and the timing chain was never touched, the chain could fail and you will end up with a totaled engine.

VANOS Solenoid Failures

Another common failure point on this engine is the VANOS system. This VANOS system is the variable valve timing.

For this system to work, there are two solenoids that activate and deactivate whenever there is a need. By doing so, they help advance or retard the timing of the camshafts.

And what happens is that these solenoids can become defective and start to malfunction or completely fail.

Whenever there is a malfunction of these solenoids, you will notice the check engine light. In addition to this, the engine will run rough and there will be a drop in fuel economy.

It is important that you react quickly and replace the faulty solenoid with a new one and you will be good to go.

VANOS Solenoid Seal Leaks

Another problem with the VANOS system on this engine specifically is connected to the VANOS solenoid seals that tend to leak.

There are two seals on each of these solenoids. These seals are made out of rubber and over time, they can start to allow oil leaks to develop.

This will result in loss of oil and the VANOS system will not perform as it should. You will also get the check engine light and a code concerning this system. Luckily, it is not very expensive to get them replaced.

Ignition Coil & Spark Plug Failure

Ignition coils and spark plugs are also susceptible to failure on these engines. The coils tend to go out at 100,000 kilometers.

So, there is a big chance that you will need to get a new set sooner or later. What is worth noting is that whenever you need to swap the coils, you should also do the spark plugs.

This way, you will be sure that the new coils will work perfectly. Spark plugs are really cheap.

Symptoms associated with this problem are engine misfires, check engine light, rough idle, and low engine power.

PCV Valve Failure

PCV valve or CCV valve as it is known in the BMW community is another very common failure point on these engines.

This is the crankcase ventilation system valve. This valve has the task to purge the gasses that were collected from the crankcase into the intake manifold in order to burn.

This is a good system but the CCV valve is notorious for failing on these engines. Whenever this component malfunctions, you will get a check engine light, the engine will run poorly and you will also get oil leaks from the side of the engine since there is too much pressure and this pressure has to exit from somewhere.

Luckily, this PCV valve is not very expensive and can be replaced for a good price.

Engine Is Prone To Overheat & Consume Oil

This engine is also prone to overheat and once it overheats, it starts to consume a lot of oil. This is why it is really important not to let the engine overheat by any chance.

If it overheats once, there will be damage done to the internals and this will let the engine consume more oil than normal.

So, this is one thing to have in mind. Also, higher engines consume a lot of oil as well. Especially well above 150,000 km.

Oil Leaks

Oil leaks are another common thing on these BMW engines. Basically, most BMWs engines tend to have oil leaks.

These leaks usually develop around the oil filter housing or on the valve cover. If the gasket is old, it will start to allow oil to leak.

In addition to this, oil leaks from the timing cover gaskets and oil pan are also very common on these engines. So, it is very advised that you check the engine for leaks before you buy the car.

Coolant Leaks

And last but not least are the coolant leaks. These were the times when BMW was not regarded as a quality company when it came to cooling systems.

They tend to leak coolant everywhere, especially from the hoses and radiators. This is why it is very much recommended that you always monitor the coolant level and make sure that there are no leaks under the car. If there are, you will have to do a repair. If you don’t fix the problem, the engine could overheat and cause a lot of problems.

Which Models Include The BMW N40 Engine?

This engine was included in the following applications:

  • 2001 – 2005 BMW E46 316i
  • 2001 – 2005 BMW E46 316ci
  • 2001 – 2005 BMW E46 316ti


Which BMWs have the N40 engine?

This engine is included in the E46 platform made by BMW between 2001 and 2005. The engine was only included in the entry level 316 models. These were the compact, coupe, and the 4-door saloon.

What Are The Common Problems With The BMW N40 Engine?

This engine has many problems, this is one of the reasons why BMW replaced it. The biggest problem is probably the timing chain tensioner failure that was sorted after 2003. Another common problem is the issue with the VANOS seals that tend to fail. This engine also has problems with the PCV system and the PCV valve which often fails. In addition to this, problems with the ignition which include spark plugs and coils are also very common.

Is The BMW N40 Engine Reliable?

This engine is average in terms of reliability. It is not a bulletproof engine and has some issues. But what is good is that this engine does not have the Valvetronic that was added to the N42 engine. This system was plagued with problems during the first production years and was very expensive to fix, that is one positive side with this engine. 

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