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Serpentine Belt & Belt Tensioner replacement -- N62 (545i)

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Serpentine Belt & Belt Tensioner replacement -- N62 (545i)

Old 10-25-2010, 11:24 PM
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Scroll down past the story if you'd like to save some time.

So my 545 started squealing LOUD one day and I assumed it must have been low oil or the water pump dying out. Added oil, topped off the radiator tank, and still no progress. Took a look at my water pump/alternator belt and all the ribs looked okay...pressed down on the belt and it popped a bit, like something was loose. Drove around some more and the noise started to get louder and louder. Back under the hood with closer inspection revealed a chunk missing from the belt.

How the heck does this happen?
Serpentine Belt & Belt Tensioner replacement -- N62 (545i)-00.jpg

I purchased a new Conintech belt from Pelican parts (there's a warehouse here in Northern California), and it was shipped to me a couple days later. Ordered an A/C belt with a new paper air intake filter while I was at it. Haven't changed the A/C belt yet by the way...

Tools and items you'll need for the serpentine belt change:
(1) Serpentine belt (I'd recommend Conintech)
(1) T-60mm star bit socket
(1) 16mm bit socket
(1) Make-shift torque bar (1" x 18" iron bar from Lowe's)
Serpentine Belt & Belt Tensioner replacement -- N62 (545i)-03.jpg
(2) Socket wrenches
(Lots) of patience..

Instructions:

1. Start by removing the intake tubing. Unscrew the two hose clamps on both ends, wiggle each end until they pop out of the throttle body and intake box
Serpentine Belt & Belt Tensioner replacement -- N62 (545i)-01.jpg

2. Fit the 16mm bit socket onto the bolt holding in the belt tensioner
Serpentine Belt & Belt Tensioner replacement -- N62 (545i)-04.jpg

3. Lefty-loosey until the belt tensioner is loose enough to come out of the notches that keep it in from moving. You'll then be able to move the tensioner out and to the left to loosen the belts.

4. PLEASE don't uncap the pulley on the belt tensioner and undo the T-50mm star bolt, I searched around on here and the posting from "xxxxx" was wrong. Loosening the pulley does nothing to loosen the belt, it'll just frustrate you later. I spent a few trips to Autozone to get the bit heads correct.

5. Mark down the layout of all the pulleys, top and bottom and which side has ribs and which side is flat.

6. Remove the belt once you've jotted down layout of the belt and its pathway. I'd work your way from bottom up, getting the biggest pulley to the alternator and lower belt pulley around to the water pump leaving the upper belt tensioner loose.

7. Wrap the belt around the belt tensioner, and start tightening the 16mm bolt until there's little play in between the belt tensioner and the two metal notches (from the engine block) that keep the belt tensioner from moving.

8. The belt should be getting tight as you try to turn the belt tensioner counter-clockwise by hand. You'll notice that as you turn counter-clockwise, the pulley for the belt will move to the right, thus tightening the belt

9. Insert the T-60mm star bit into the female end on the belt tensioner
Serpentine Belt & Belt Tensioner replacement -- N62 (545i)-02.jpg

10. Attach both the socket wrenches into the sockets, I had to use a small extension for the 16mm bit socket for enough clearance
Serpentine Belt & Belt Tensioner replacement -- N62 (545i)-05.jpg

11. Fit the breaker bar over the wrench that connects to the T-60mm star bit socket. You're going to need this added torque to pull the belt tensioner outwards.
Serpentine Belt & Belt Tensioner replacement -- N62 (545i)-06.jpg

12. MAKE SURE THE BELT TENSIONER IS LINED UP IN BETWEEN THE TWO METAL NOTCHES BEFORE YOU TIGHTEN DOWN THE 16mm BOLT!!!

13. If it isnt...loosen the 16mm bolt slightly so there is a bit more play, do not make it loose.

14. You're going to be turning the wrenches in OPPOSITE directions. The T-60mm should be going counter-clockwise (loosen), and the 16mm should be going clockwise (tighten).

15. Pull on the torque bar slowly, pull quickly and you may break the belt tensioner or the notches on the engine

16. As you pull on the torque bar, the belt will tighten. When the belt feels tight enough, hold on the torque bar and tighten the 16mm bolt TIGHT.

17. Once it's tight enough, let off the torque bar on the T-60mm end. I then took the torque bar and placed it over the 16mm wrench to really tighten down that bolt.

18. Press down on the belt, you should only be able to depress the belt slightly. If it depresses close to an inch or you feel a pop, then you need to loosen the 16mm bolt, and pull the belt tensioner more.

==============================================
IF YOU HAVE A BROKEN BELT TENSIONER LIKE I DID
==============================================
I purchased a new INA (OEM from Germany) belt tensioner from Winchester Auto Parts; the only auto parts store I know locally that has this part and for a decent price. Unfortunately, there's only a handful of Winchester Auto Parts shops here in the Bay Area. Price for a new one was $80 plus tax, STEALer wanted $145 plus tax.

1. Do all the steps above up until step 6.

2. Remove the 16mm bolt completely when you loosen it.

3. Here is what my belt tensioner looked like
Serpentine Belt & Belt Tensioner replacement -- N62 (545i)-07.jpg

4. I actually had only one metal tab broken, not sure how. Perhaps this is how the belt got chewed up in the first place? Anyways, I pulled too hard on step 14 and broke the other metal tab.

5. Side-by-side comparison. New on left, old on right
Serpentine Belt & Belt Tensioner replacement -- N62 (545i)-08.jpg

6. The belt tensioner is supposed to have a metal bar to keep the spring housing lined up, mine did not have this.
Serpentine Belt & Belt Tensioner replacement -- N62 (545i)-09.jpg

7. Again, align the top metal tab in between the two metal notches from the engine, counter-turn the T-60mm socket while turning the 16mm as soon as the belt is tight enough, and the metal tab is in between the two metal notches.


Viola!

Drivable car again!
Serpentine Belt & Belt Tensioner replacement -- N62 (545i)-10.jpg

Let me know if you guys need help, anyone is welcome to come by my place to get either of these done -- San Jose, CA. Just take me out to steak or give me a full-tank of gas or something.

Cheers!
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Old 10-26-2010, 03:33 AM
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Awesome write up! thanks. May come in handy someday.
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Old 10-26-2010, 11:01 AM
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You probably should look into replacing the main belt around 100,000 miles. Need to WD-40 the pulleys later..
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Old 11-02-2010, 09:24 AM
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Nice work!
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Old 11-02-2010, 09:34 AM
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Originally Posted by ck-e60 View Post
You probably should look into replacing the main belt around 100,000 miles. Need to WD-40 the pulleys later..
what??
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Old 11-02-2010, 08:02 PM
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Originally Posted by turboawd View Post
what??
I found a leak right underneath the belt pulley on the belt tensioner, looks like water and i think its causing the pulley to squeal a bit? going to replace the water pump soon, just haven't found the time to do it yet.
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Old 11-03-2010, 07:31 PM
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Originally Posted by ck-e60 View Post
I found a leak right underneath the belt pulley on the belt tensioner, looks like water and i think its causing the pulley to squeal a bit? going to replace the water pump soon, just haven't found the time to do it yet.
where are you going to spray wd40? hopefully not the belt or the pulley surface where they ride on.
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Old 01-15-2011, 03:56 PM
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I'm pretty novice when it comes to engine repairs for BMW. My 2007 525i belt is about to come off one of the pulleys. And look at the second picture. Did the bolt snap off??? How does this happen??! San Jose you said?? Tank-a-gas?? I can use your help!
Attached Thumbnails Serpentine Belt & Belt Tensioner replacement -- N62 (545i)-belt.jpg   Serpentine Belt & Belt Tensioner replacement -- N62 (545i)-bolt.jpg  
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Old 01-15-2011, 07:40 PM
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Kinda hard to tell, the N62's have a belt tensioner that tightens and loosens the belt. Give me an hour to find out how your engine is laid out, I'm having Hot Pot right now.
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Old 01-23-2011, 10:34 AM
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Great right up! I may have to take you up on that Tank of gas or steak dinner!
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