What is the most common and costly problem found in BMW 4 Series vehicles?

I have recently purchased a BMW 4 Series and I am concerned about potential technical issues. What is the most common and costly problem that owners of this model have encountered?

The most common and costly issue found in BMW 4 Series vehicles is engine failure.

It is important to regularly maintain your vehicle and address any warning lights or unusual sounds as soon as possible to prevent engine failure.

A common cause of engine failure in BMW 4 Series is a faulty water pump. Regularly check your coolant levels and replace the water pump if necessary.