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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > When did you replace your serpentine belt, idler pulley and belt tensioner?



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      06-17-2020, 09:15 PM   #1
mosaud98
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When did you replace your serpentine belt, idler pulley and belt tensioner?

The previous owner replaced the belt tensioner at 59k miles in 2017 (idk why he didn't just get the belt and idler pulley replaced then). But, I am at 71k right now. No visible cracks or fades on the belt. If I do go on and replace the belt, should I replace the Idler Pulley along with the belt?
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      06-18-2020, 02:24 PM   #2
hassmaschine
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Did both of ours at around 100k. In both cases, the belt was just fine but the tensioner was starting to sag. I think I bought a new belt for the E91, but ended up reusing it on the other car, because it was in perfect condition, I didn't see the point. at 71k as long as the tensioner is fine, I'd just leave it be - the belts aren't usually the cause of failure.
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      06-18-2020, 03:49 PM   #3
gearhead26
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Doing mine this weekend. 40k miles on the car. Car is about 9 years old, but belt looks to be in pretty good shape. Since I am doing some other work on the car, I figured I might as well do this as well too.
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      06-18-2020, 03:52 PM   #4
matteblue3er
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When the front lip of the belt is walking off the front lip of the tensioner pulley wheel, it means the tensioner is on its way out.
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      06-18-2020, 09:02 PM   #5
Emilime75
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Doing mine right now as part of a major maintenance package, I'm at 62k. Nothing wrong with them, just want peace of mind and I was already doing a bunch of other work on it.
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      06-18-2020, 09:13 PM   #6
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I did mine at the same time I did my valve cover and OFHG since its a messy job doing them.
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      06-27-2020, 06:14 PM   #7
Chemdad
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Pulley and tensioner went out at 118k miles on my 2006 325i with the n52 motor
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      06-27-2020, 08:45 PM   #8
CTinline-six
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Quote:
Originally Posted by matteblue3er View Post
When the front lip of the belt is walking off the front lip of the tensioner pulley wheel, it means the tensioner is on its way out.
This.
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      07-08-2020, 12:50 PM   #9
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Quote:
Originally Posted by Emilime75 View Post
Doing mine right now as part of a major maintenance package, I'm at 62k. Nothing wrong with them, just want peace of mind and I was already doing a bunch of other work on it.
What other maintenance?
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      07-08-2020, 12:58 PM   #10
Efthreeoh
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Replaced the belt twice at 100,000 intervals and replaced the tensioner at 300,000 along with a new belt.

Tensioner was still in good shape, kept it as a spare.
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      07-08-2020, 01:57 PM   #11
Emilime75
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Quote:
Originally Posted by otitxn View Post
What other maintenance?
Valve cover, gasket and bolts.
RB external PCV with Mishimoto low side OCC.
Tapped/plugged the head ports.
Spark plugs.
Coils.
Walnut blast.
Intake manifold gaskets.
Throttle body gasket.
OFHG.
OCG.
OC line o-rings.
Starter.
Engine to chassis ground strap.
Serpentine belt, tensioner and both idler pulleys.
Aluminum coolant hose flange.
CSF aluminum radiator(car had a slow leak I could not locate, and the CSF came up for sale locally for a great deal, haven't had a leak since so it looks like I got lucky).
Partial coolant flush(refilled with distilled water only, will drain again and refill with the proper coolant mix).
2 oil changes(one during the above service, 2nd 120 miles later).

The car wasn't really having any major issues, just didn't seem as "smooth" as I felt it should. Feels way better now, but still not perfect. Looking at injectors next.
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      07-08-2020, 11:29 PM   #12
pizza_nightmare
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170000

I did mine at around 170,000. Something was squeaky at idle, I did it all with the FCP Euro kit.
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      07-09-2020, 02:21 AM   #13
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Quote:
Originally Posted by matteblue3er View Post
When the front lip of the belt is walking off the front lip of the tensioner pulley wheel, it means the tensioner is on its way out.
+1.

I replaced tensioner pulley when belt begin to slide towards the front - after 11 years & 92K miles.
Purchased and installed complete CRP set (belt, tensioner & idler pulley).
Kept old belt and idler pulley as a spare (both were in very good condition).

Short video of my aging tensioner pulley - notice the belt is roughly 2-3 mm off the pulley:
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