In the early 2000s, BMW launched a new line of engines, all of which are denoted by the letter N at the beginning of the index. The first was the N42, which received the whole package of innovations: from the aluminum block to the Valvetronic system, which regulates the height of valve lift. The N42 engine is available in 1.8-liter and 2.0-liter displacements. Also in the same year 2001, a rare 1.6-liter N40 engine was introduced. It did not have a Valvetronic system.
Later, in 2004, the N40 engine was modified and turned into a unit N45 with an output of 116 hp. Also in 2006, a charged 2-liter version of this engine with an output of 173 hp was presented on BMW 320si (E90). This 2-liter version is based on a cast-iron block and seriously strengthened. The N45 engine was installed in two BMW models: the E87 “one” and the E46 and E90 “three” from 2004 to 2012.
Engines N43, N45, N46 have the same cylinder diameter – 84 mm, piston stroke is different.
In a nutshell, the N45 is a relatively simple in-line atmospheric “four”. Without Valvetronic system and with “usual” distributed injection. We will tell about its features and problems on the example of its 1.6-liter version, taken from BMW 116i of 2007 release with a mileage of 160 000 km.
In general, the engine N45B16 is the simplest of those that can be found on the 1st and 3rd series. And relatively survivable. In addition to not having Valvetronic in its cylinder head, it also lacks EGR, variable length manifold and balancer shafts.
Starter
One of the common reasons that the N45 engine (and other BMW inline fours and sixes) doesn’t start the first time or starts with a grinding noise is the failure of the starter bendix.
In the bendix over time, the springs sag, rollers are worn. Because of this, the bendix simply does not grab the flywheel crown and can not crank the crankshaft. Also failures are associated with lack of grease or its contamination. And the grease for the bendix needs quality and heat-resistant. The bendix can be repaired or the entire starter can be replaced with a used one.
Generator
The generator of the N45 engine is equipped with an overrunning clutch. It is not eternal: it can wedge, because of which from under the hood you will hear grinding and noises when the engine is running or at the moment of its stopping.
Engine and gearbox cushions
The BMW N45 engine is very light, but its cushions can sag as early as 100,000 kilometers. This causes vibrations. But the automatic transmission cushion, if paired with the engine, tears even more often.
Starting revs
The N45 engine may have not just floating, but jumping revolutions: after a cold start they rise sharply to 3000 rpm, fall and then everything repeats. This problem is solved by ECU re-flashing at the dealer.
Oil leaks
The BMW N45 engine leaks oil quite actively.
The leak is caused by the valve cover gasket. Usually sweating starts in its rear part above the exhaust manifold.
The sealing rings under the Vanos phase shifter valves, the oil filter “cup” seal, and the vacuum pump leak. Another important sore spot is the tensioner bolt of the timing chain guide bar. But about it a little later.
BMW N45 engine does not start
Another not uncommon reason that the engine N45 does not start is a problem in the timing gear. These problems are not few and all of them are related to chain stretching or sagging, which causes camshaft and crankshaft timing mismatches. The N45 engine chain is quite thin and weak, stretches and needs to be replaced every 100,000 km.
Plus wire
The BMW 1 Series, as well as the E90 Triple, BMW X1, Z4, has a weak point – the plus wire, stretching from the battery, which is in the trunk, to the fuse box. In the area of the rear right wheel, the long plus wire is connected to the short one through a terminal. This place is very poorly protected from dirt and salt. Over time, the wire simply rots and falls off from the lug.
In this case, the N45 engine will not start, but can easily come to life from a cigarette lighter. Also, the engine can stall on the move, and all electronics is turned off – the contact is lost.
Also, if there is just a bad contact, the engine goes into emergency mode (weak pull), and there are errors indicating a faulty ECU.
Plus wires on BMW were changed under warranty and protected with dust covers.
Plastic plug on the cylinder head
At the back of the cylinder-head there is a plastic cap covering the cooling ducts. When the pressure in the cooling system rises, this plug cannot withstand and leaks. And the pressure can jump because of the valve in the expansion tank lid.
Throttle valve
If the BMW N45 engine has errors on air sucking, then in most cases, the throttle gasket is to blame. It needs to be replaced. Otherwise, the throttle on the N45 motor usually does not cause problems.
Ejection pump
Only the N45 engine among its brethren is equipped with an intake jet pump, which creates rarefaction for the brake booster. It essentially amplifies the rarefaction that exists in the intake manifold. It usually lasts a very long time and can only get clogged due to crankcase gases.
Crankcase gas vent valve diaphragm
Due to the failure of the rubber diaphragm of the crankcase gas vent valve, oil begins to enter the intake and consequently the combustion chambers. The diaphragm can be checked relatively easily: on a running engine, you need to unscrew the oil filler plug. It should be sucked due to the discharge. And if you remove the plug completely, the engine should start shaking, running unevenly. These are good signs – the diaphragm is intact.
If the engine does not start “shaking” with the unscrewed plug, the diaphragm is destroyed. On the N45 motor, it is built into the valve cover and is factory changed entirely with it. The cover costs about 350 dollars. But there are repair non-original diaphragms on sale. To replace the plastic “hatch” over the diaphragm should be well heated and carefully removed.
Ignition coils
Ignition coils are not bad – they can withstand a mileage of 100 000 km. In case of failure, there are errors indicating ignition misses in the corresponding cylinder.
One of the causes of failure of phase shifters Vanos
The Vanos phase shifter clutches on the BMW N45 engine are hydraulic and structurally similar to those on many brands of engines, from Renault to Volkswagen.
Oil is supplied to them through channels running in the very first journals of the camshafts. There on the camshafts there are also metal ring inserts with locks. It happens that the locks on the rings are destroyed, they twist and block the flow of oil to the phase shifters. They begin to rustle, there are errors on camshaft sensors (unreliable signals), the engine does not run hot at all. Also oil starts leaking through the camshaft oil seals.
Vanos phase shifter valves
Vanos phase shifter valves can leak oil through the connectors, because of which their work is disturbed, there are failures in the regulation of timing, the engine begins to work with noticeable vibrations. Also may clog valve nets, but this trouble is eliminated by removing the valves and cleaning them with a means such as carburetor cleaner.
Vanos clutches
Vanos clutches themselves are quite reliable and durable. But their life can be shortened by poor quality oil. In this case, scoring occurs on the clutch body, in the places of friction with the edges of the blades. Also oil channels can be broken. In this case, the couplings will have to be replaced.
Transmission timing chain
The chain on the N45 engine requires attention at a mileage of about 100 000 – 150 000 km. It can be stretched, and then during operation the engine will be ringing and subtle clanking – this extraneous sound is clearly audible.
But in addition, the tensioner plates often wear out. Plastic, or rather fluoroplastic, from which they are made, can not withstand the impact of hot oil, which is heated up to 120 degrees. In such conditions, the plastic becomes brittle and quite easily destroyed.
And this destruction occurs in the following scenario: the hydraulic tensioner wears out and jams, the tension of the chain weakens, and it begins to hit the guide. After a series of impacts, the guide fails and splits. Parts of it, splinters and even chips fall into the oil pan.
Of course, they fall into the oil inlet. The oil intake and its grid on the BMW N45 engine are made of almost the same plastic, and therefore can not only clog, but also break through. In short, plastic fragments can get into the oil pump, which will break them into even smaller pieces. They will spread further in the oil system, and the oil filter can not always hold them, because its paper will simply tear under their influence. In general, plastic bits and chips get everywhere, which causes the liners to rotate.
And of course, if the chain is sagging or severely stretched, the timing is off. The chain can also break with all the capital consequences that come with it.
The chain repair kit costs about 250 dollars and it is better to change it together with the tensioner (about $80), because a tired tensioner will soon “talk” the guide bars.
Chain tensioner
The chain tensioner is made in the form of a bolt with a movable piston. It can be changed very easily. It does not last long. Usually, the first thing that BMW owners with N45 engine do when they hear chain scratching in the morning is to change this tensioner.
In addition, because of this tensioner bolt at ridiculous mileage, from 15 to 50 thousand kilometers, the engine N45 was deprived of almost all the oil. The bolt was simply unscrewed. And since oil is supplied to it under high pressure, it seeps out quickly. The oil level can drop to the minimum level literally within 15 km of travel. The tensioner bolt itself is unscrewed due to a factory defect of the o-ring. The old-style ring has a shape like with petals on the outer circumference. The new ring is just flat on both circumferences.
Oil consumption
Oil consumption for the N45 engine is quite a common story. Most often, oil gets into the combustion chambers due to blistered oil caps. Often oil consumption begins at a mileage of 100 000 km and quite sharply. The car begins to smoke in the morning at cold start, and messages about the need to refill the oil appear every 3-4 thousand km.
The oil caps can be cured only by replacing them, and frequent oil replacement every 7-8 thousand km can prolong their life.
You can diagnose oil burning on the engine by unscrewing the spark plugs – if the electrodes and extreme threads will be in oil, it is time to change the oil caps.
Although oil burning may occur due to oil rings or torn membrane of the crankcase ventilation valve.
In any case, the root cause of oil burn is high – 95 degrees – thermostat temperature, at which in the engine N45 oil literally boils and quickly degrades. The problem is aggravated by contaminated radiator honeycomb, sluggish city driving mode and saving on oil.
The N45 engine has no oil dipstick or oil guide tube. The oil level is measured by the oil level sensor. The measured value is displayed in the instrument cluster.