[Grease23]

I'm curious as to why so many are recommending and doing this. I've probably put well over 2 million miles on various cars with serpentine belts. Several of them went 250K plus miles. I've had to replace a belt once, but never a tensioner or pulley on any vehicle.

Is it because BMW tensioners (and pullies) are uniquely short lived? Or is it that the damage should a belt get wound/sucked into the crank so catastrophic that people don't want to take a chance on it?

[E93Dude]

Originally Posted by Grease23

I'm curious as to why so many are recommending and doing this. I've probably put well over 2 million miles on various cars with serpentine belts. Several of them went 250K plus miles. I've had to replace a belt once, but never a tensioner or pulley on any vehicle.

Is it because BMW tensioners (and pullies) are uniquely short lived? Or is it that the damage should a belt get wound/sucked into the crank so catastrophic that people don't want to take a chance on it?

This.

The serpentine belt is cheap and easy to replace. The pullies are, as well. A failed belt, if it gets mangled by the crank and sucked into the engine, causes an epically big mess to clean up, and that is the best case scenario. It is a cheap fix and insurance policy. If you choose to do it, take the extra time to put on a crank plate, which would prevent this problem from ever happening in the future.

[Grease23]

Who makes the plate? Thanks.

[E93Dude]

Originally Posted by Grease23

Who makes the plate? Thanks.

https://www.fcpeuro.com/products/bmw...SABEgLVq_D_BwE

Google BMW Crank Plate and you will see lots of choices. FCP Euro, Turner Motorsports, ECS Tuning all have offerings. Amazon, too.

[Grease23]

Just to follow up, on a 328i with the N51 engine, replacement is easy. Other than removing the two screws that hold the air duct to the front of the car, the job can be done if you have decent short extensions. You don't have to do anything under the front of the car (as is apparently required on some others) you don't have to take out the air box, and you don't have to take out the electric fan.

Make a good drawing of where that belt snakes around, and make the last move putting it over the tensioner itself with the pin inserted as it comes new. Then tension it a little and take out the pin.

[mattanderson]

Originally Posted by Grease23

. . . you don't have to take out the electric fan.

To each his own, but I recommend removing the fan. There's only 1 bolt to remove, and it makes the whole job easier.