Replacing a Serpentine Belt: 2009 BMW 328xi

  • Thread starter KodyWallice
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May 7, 2021
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What’s one tool set most people never have any reason to purchase? That’s right. A Torx socket set. In general, most things homeowners need to repair have nothing to do with Torx. If you own a foreign car, especially a BMW for that matter, and you plan on making repairs yourself, you better grab yourself a set. Trust me, Torx is all over the place on these cars.

I seem to have gotten oil on my serpentine belt.

After replacing the oil cap gasket, changing the oil and stopping the leak, I was rather proud of myself. I thought things would be smooth sailing. And they were – for a while. A month or two after stopping the oil from leaking out of the oil filter housing though, I began hearing some sort of a groan that emanated from under the hood of the car. It was cyclical. Sort of like, “groan…groan…groan.” It was actually pointed out to me by a friend. He said, “Looks like you have a squeaky belt there buddy.” I thought to myself, “How in the heck do I have a squeaky belt? There’s only one belt and it’s a serpentine.” It was odd because I never thought about a serpentine belt slipping before. I thought that only happened to v-belts.

As it turns out, serpentine belts on BMWs start slipping and squeaking after they’ve been introduced to oil. Oil that comes from a leaky oil filter cap. I did some digging online and found that almost every single person who had to change their serpentine belt on these cars had to do so after they experienced the same exact oil leak as the one I experienced. At least I had a lot of company and the source of the problem and its repair were no mystery.

New serpentine belts for these cars are only about $20. The thing is, and you’ll quickly learn this after making these type of repairs, it’s always better to replace everything that surrounds the offending part as well as the offending part itself. In this case, serpentine belts often came as one item in a kit. The kit includes the belt, an idler pulley and a belt tensioner. I found a very standard kit on a site called RockAuto for about $88. I ordered it and it showed up in our mailbox within a few days. I’m sorry, I’m still in awe of the internet. I don’t know how it got so magical and how it lets me receive auto parts at the house by punching a few keys on my keyboard. Anyway.

Take a look at the old serpentine belt, the belt tensioner and the idler pulley. You can even see the gunk from the oil leak on the tensioner.


And here’s a close up of the inside of the serpentine belt. It still looks a little oily even after I cleaned it with Simple Green a few times. I guess I need to use something stronger because the front of the engine is still dirty and it’s annoying me.


After I ordered the parts, I realized that I’d need some tools I didn’t have yet to make the repair. This is where I always get excited. I seem to have a small tool addiction that was most likely handed down to me from my father. Any time I get to add to my collection, I get all sorts of energized and I look all over the place for exactly what I need. It’s sort of like window shopping all day and then at the end, making the purchase that fills my heart with joy.

Unfortunately, there isn’t much selection when it comes to Torx sets. I needed a few specific sizes for this job, but knew I’d likely need additional sizes in the future. While avoiding the really expensive options, such as Mac Tools and Snap-On, I decided to go with something that cost me only a hair less than $60 from Amazon. It’s a 60-piece set and it includes not only the Torx bits, but also the Torx sockets. It was perfect for my uses. Take a look at this beautiful set.


Here's the entire set.


Here’s an example of a Torx bit.


And finally, here’s an example of a Torx socket.


Yes, that’s my hand.

The sockets in this set range from E4 all the way to E24, which is pretty decent for something like this. More importantly are the bits. They range from T6 through T70. There are also a few TT and TP (tamper proof and Torx Plus) sizes thrown in as well, which is really cool.

As it ends up and after watching many videos of the repair online, the entire ordeal only took me about 45 minutes to complete. I was going to post something describing that in detail, but the photos would have been horrible. If you have to make this repair and are interested in learning all about it, I can point you in the right direction. I can even lead you to the videos that helped me out. Just remember, you’ll definitely need a Torx set (more specifically, the T60 driver to loosen the belt and the e14 driver to tighten the tensioner bolt) and a torque wrench. The torque on the tensioner bolt is 25NM, plus 90 degrees. This means that you have to tighten the bolt to 25NM and then mark the bolt with a Sharpie. After that, continue tightening the bolt until you turn it an additional 90 degrees. I know, this is weird and concerned me. Just do it.

The torque for the idler pulley is a straight up 40NM, with no additional angle torque.

Anyway, I just thought I’d share some new tools with you as well as the latest car repair I pulled off. I love completing projects like this that have such a positive effect. I no longer have to listen to that squeaky groan from under the hood anymore. Now, the car is nice and quiet. It purrs like a kitten. Can you believe it’s a 2009 and has fewer than 40,000 miles on it? Crazy.

Thanks for reading!