BMW 740iL Loud screeching noise when I start the car Inspection at your home or office.

Common reasons for this to happen:

Drive or auxiliary belts are worn

The most frequent cause of a car making screeching sounds is that the drive belts or auxiliary belts are old and need to be replaced. When your belts start to wear out and fray, the oils within them will come out and encourage all forms of screeching and slapping sounds.

Tensioners and pulleys are worn

The pulleys and belt tensioners that keep your belt in place can also wear out over the course of time. The tensioner helps keep the belt in place and under the right alignment, while the rubber inside your pulley helps absorb the vibrations that are generated from your engine. If this rubber part wears out, your belt may also begin to have wear issues.

Wrong torque, alignment or belt size

If the torque and alignment on the belt tensioner and pulley are incorrect, your belt may not have the proper pressure on it. Also, there are times when the wrong size belt has been installed. Different engines require different belts. If a belt is too big, it will start making sounds as well.