Background
BMW has a long history of manufacturing highly efficient 4-cylinder engines since at least the 1930s. The one we see most commonly with timing chain issues is the N20/N26 engine.
The N20/26 is a technologically advanced, powerful, and very fuel efficient power plant. As it is in such widespread use, its weak spots are well-known, and proven solutions have been developed to address them. Having worked in hundreds of them, we at CarHavn EuroTech know them very well.
Like a fine Swiss watch, your engine has a precise internal mechanism where the power generated in the pistons is transmitter to the camshafts. The timing chain job is to transfer that power to the crankshaft, which turns the transmission. This needs to happen very precisely, as the engine turns approximately 500-7000 times a minute.
The Issue
Even though timing chains were supposed to be lifetime, reality has shown that they need to be replaced in the N20/N26 engine as early as 70K miles, and every 100K miles thereafter. The reason is a combination of design choices, materials, and the horrible recommendation to change oil every 10K miles.
The most common condition is a stretched chain due to timing chain guides made of plastic material prone to premature failure. With excessive slack, a timing chain is very dangerous, as it risks getting out of sync and destroying the engine internally.
Symptoms
A failing timing system has some specific signature symptoms in this engine.
- Rattling or whine in the timing chain area
- Elongated crank times (sometimes)
- A Check Engine Light on (sometimes)
- Diagnostic Trouble Codes set in the car's computer (sometimes)
The only sure way to check for timing chain stretch is to use ISTA, BMW's repair software, to run a 'test plan' to measure a specific value in the engine computer.
