Peugeot 4008 belt tensioner failure

I also have a 4008 and had a similar experience. Is it making a whining or chirping noise, especially when the engine is cold? Also, have you checked the serpentine belt for wear or damage? Sometimes a worn belt can cause the tensioner to work harder and fail prematurely. How old is the belt?

Yes, there's definitely more engine noise than usual, especially in the morning. I haven't checked the belt itself closely, but it looks okay at a glance. I don't know exactly when it was replaced.

Okay, the extra engine noise is a concerning point if your belt-handover no longer works! Given all of this, my advice – and I'm not a professional mechanic – would be to get it checked out by a workshop as soon as possible. Continuing to drive with a faulty tensioner is risky, as it could cause further damage to the belt drive system. In my case that also appeared to be related. It's better to be safe than sorry.

I took it to a workshop to have a look. You were right on the money. Needed new tensioner pulley and serpentine belt. Cost me 455€, all in.