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Viano Diesel Belt Tensioner Issue

Morning. I've got a head-scratcher with my 2011 Mercedes Viano diesel. It's done 137688 km. Recently, I've noticed the belt tensioner isn't doing its job the belt handover isn't working anymore, and the serpentine belt seems loose. I've been getting a noticeable engine noise too, especially at lower RPMs. I've checked the idler pulley, and it seems okay, no excessive play or noise. My suspicion is that the belt bringer itself is defective. A local mechanic quoted me around 455€ for the repair. Does this sound right, and is there anything else I should be checking before I commit to that cost? This belt drive issue is really bugging me.

A 2011 Mercedes Viano diesel with 137,688 km had issues with a loose serpentine belt and noticeable engine noise, particularly at lower RPMs. The initial suspicion was a defective belt tensioner, as the idler pulley appeared fine. After confirming the belt was in good condition and pulleys were aligned, the faulty belt tensioner was identified as the likely cause. Replacing the belt tensioner resolved the noise and belt issues.

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4 comment(s)

Could be the tensioner. Is the belt worn? Sometimes a worn belt will cause the tensioner to work overtime and fail prematurely. Check the alignment of all pulleys too. A misaligned pulley can also cause excessive wear and noise.

Thanks for the quick reply. The serpentine belt itself looks to be in reasonable condition, no obvious cracks or fraying. Regarding the alignment, is there a simple way to check that without specialized tools? I'm trying to rule out all the simple things before I shell out for a new belt tensioner.

Visual inspection is usually enough. Use a straight edge across the pulleys. If it's significantly out of alignment, you'll see it. Otherwise, if the belt is good and pulleys seem aligned, a faulty belt tensioner is the likely culprit. Consider getting a second opinion from another workshop if you're unsure.

Appreciate the confirmation. I took it to another mechanic, and they agreed it was the belt tensioner. Got it replaced, and the engine noise is gone, belt handover is working fine now. Thanks again for your help!

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MERCEDES

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VIANOVITO