The M50, M52 and M54 engines are close “relatives” that have gone through several stages of evolution.
The first of them – M50 – appeared in 1989. It was the first BMW engine with a plastic intake manifold. It was produced in versions with a volume of 2.0 and 2.5 liters. A chain is used in the timing drive, and hydrocompensators are used in the cylinder head. In 1993, the modernized version M50TU was equipped with a phase shifter on the intake camshaft.
The M52 engine began to be installed on BMW cars in 1995. This motor was also available in a third volume variant – 2.8 liters. The main difference between the 52nd engine and the 50th is the aluminum cylinder block, thanks to which the engine “dropped” 30 kg of weight. The aluminum block of the M52 engine created a lot of trouble for the owners and the company itself. The thing is that Bavarian engineers from the best motives applied an innovative coating of cylinder walls – nikasil. That is, there were no liners in the aluminum block of the M52 engine, the cylinders were milled, and nickel-silicon alloy with a thickness of about 4 microns was applied to their surface. Nickel-silicon coating was widely used and is still used in motorsports, it is a very durable compound, moreover, it reduces friction losses. But in the 1990s, many European countries still sold gasoline containing sulfur. Sulfur turned out to be very poisonous for nicasil, so the coating of the cylinders of such an engine was destroyed: pistons “scuffed” the walls of the cylinder, in contact with the aluminum alloy from which the block was cast. By the way, specially for the North American market BMW M52 engine (for all models, except BMW Z3) was produced with cast iron block.
In any case, having changed thousands of engines under warranty, in September 1998 BMW released an upgraded M52TU engine with a cast aluminum block. Also on this engine appeared dual VANOS – that is, phase shifters were used on both camshafts. A system of adjusting the length of the intake tract appeared. There can be as many as two throttle plates on the M52 engine – the second one is controlled not by the driver, Traction Control – a system of traction control.
Problems and shortcomings of the BMW M52 engine
With all the legendary image of BMW engines, we can not fail to mention their shortcomings. It is true that many problems arise due to not quite attentive maintenance of these engines.
Engine overheating
For example, as far as the BMW M52 engine is concerned, it is very easy to overheat if you don’t keep an eye on the antifreeze level or if you don’t detect contamination of the radiators or if the entire cooling system is leaking. In case of overheating, at least the block head “leads” or its gasket burns through. In the worst cases, the pistons and cylinder walls “seize”, the crankshaft journals overheat and the engine seizes.
Variable length intake manifold and DISA
The plastic intake manifold has separate small and large cross-section piping. A single damper is used to switch the airflow between them, which separates the two sections of the intake manifold. The damper, its servo and the intake manifold itself are a separate intake system. The weak point here is the damper itself, which comes off its axis. In most cases it slips off the plastic spindle at its base and jams. An error occurs and the owner gets the opportunity to replace the damper before it flies into any of the cylinders.
Carter Gas Ventilation Valve
In the crankcase gas ventilation system of the M52 engine there is a problematic differential valve, in which over time the diaphragm bursts or sticking or the drainage tube is clogged. The valve must be replaced and do not delay with it, because the symptoms of malfunctions with it – oil squeezing out through the valve cover, oil seals, oil consumption, formation of poor fuel-air mixture – will progress and can lead to engine failure.
Thermostat
The thermostat with a plastic housing debuted back on the M50 engine in 1993. Of course, it went to the successor engines. The plastic housing of the thermostat warps over time, causing antifreeze leaks.
Phase shifters Vanos
Phase shifter clutches are far from eternal and when they fail, they start to crackle or rattle when the engine is running. Or revs float and power drops. However, phase shifters are repairable – there are inexpensive repair kits for them.
Lowering oil pressure
Also inherent in the M52 engine is a decrease in oil pressure with wear of the oil pump, wedging of the pressure reducing valve, “fatigue” of the valve in the oil filter housing.
Wear of the cylinder head
Oil sealing caps get tanned by 300 000 km, and when using low-quality oil, the valve guides wear out and hydrocompensators become encrusted.
Piston group
The piston group of the M52 engine is not without sin. Compared to the M50 engine, the height of piston rings is less, they wear out and lose elasticity. Problems with compression can start already at a mileage of about 250 000 km. When piston rings wear out, oil consumption increases, a lot of gases burst into the crankcase. Because of these factors, when the engine is working under heavy load, there is overheating of pistons, and valves can also burn out.
By the way, let’s get back to nikasil: many of such engines were able to avoid overhaul and lasing, because they were never filled with gasoline containing sulfur, so the nikasil coating was not threatened. However, these engines often needed to have their piston rings replaced.