What causes the noise in BMW N20 engine?
4 Answers
There are several reasons for abnormal noise in BMW N20 engine: 1. Severe engine carbon deposits: The most common cause of engine noise is excessive carbon buildup in the throttle body or fuel injectors. Solution: Clean the fuel system and check the idle control valve for carbon deposits, then clean if necessary. 2. Ignition system issues: Poor ignition system performance or faulty spark plug firing can also lead to this phenomenon. Solution: Check if spark plugs have excessive carbon buildup and replace them if needed. 3. Unstable oil pressure: Abnormal fuel pump pressure, incorrect readings from the intake pressure sensor, or malfunctioning components can cause engine noise. Solution: Check oil pressure and replace components when necessary.
I drive a BMW with the N20 engine, and since last year, there has been abnormal engine noise, mainly a rattling or chain-like metallic sound during cold starts. I asked several fellow car owners, and many have encountered issues with the timing chain becoming loose. Due to a design flaw in the N20, the chain and guides wear out quickly, and once they loosen, they start making noise and can even cause more significant damage. Additionally, if there's a humming sound, it might be due to the turbo bearings or insufficient oil causing poor lubrication. Later, I took it to the dealership, where the technician used diagnostic tools to check the chain tension and oil pressure, confirmed the fault, and replaced the parts. It cost some money, but the noise disappeared. Regular oil changes and belt inspections can help reduce such problems, and it's crucial not to delay repairs, especially before driving on highways.
Recently, my N20 engine has been acting up, making squeaking noises during acceleration or uphill driving, feeling like knocking or friction. After a preliminary check, I first looked at the dipstick—the oil level is normal, but the oil quality might be degraded, affecting lubrication and causing bearing noises or similar issues. Common causes include timing chain system failure, which is quite common in N20 engines, especially after tens of thousands of miles when the chain stretches. It could also be injector noise or a loose belt tensioner. I suggest finding a quiet place to park and listen for the noise source. If it's coming from the front hood, it's likely a belt or chain issue; if there's a whistling sound, it's probably the turbo. Don’t attempt DIY fixes—take it to a professional shop early for a diagnostic scan to prevent the problem from escalating and costing more.
The N20 engine exhibits diverse noise sources, with the timing chain being the prime suspect. Chain slack noise is particularly noticeable during cold starts, and the design makes the chain guide prone to cracking. Additionally, the turbocharger may produce a whooshing or hissing sound during high-speed operation or acceleration, often caused by bearing wear or intake pipe leaks. Insufficient oil pressure can also lead to hydraulic lifter knocking, resembling metal collision sounds. Regular observation during vehicle use, such as noting if noises occur only at specific RPMs, can help narrow down the fault range. When necessary, inspect chain tension or oil pump pressure.
