2006 - X 5MT - A/C belt keeps coming off?

T-stew · 2025-10-06T13:31:08-0400

I seem to have an issue with the AC belt coming off a couple times. Thought I'd double check here on the forum before I try it yet again or start replacing things.

Both times the belt came off towards the engine - wedging itself behind the crank pulley. Its worn or broke a hole through the timing cover right behind the crank pulley from where the belt hit it or burnt through it. Going to have to pull the crank pulley and see if I can patch it with something, or perhaps have to replace the whole timing cover.

The second time the belt came off it took the alternator/PS belt too.

The tensioner is corroded very bad, but I did get it freed up enough to adjust to seemingly good tension. The idler might have a small amount of play, not sure if that could be it, or perhaps something to do with the AC compressor? The AC was working ok until the point the belt came off. I'm a little puzzled on this one, I figure I may try to source a new tensioner bracket and idler if I can find one reasonable unless someone else has any ideas.

BruceP · 2025-10-06T13:36:31-0400

The MAIN reason a belt falls off is mis-alignment of the pullies. (assuming it is properly tensioned)

I have been known to TOTALLY REMOVE the tensioner and spend time cleaning it up and lubing the leadscrews.
While it is removed, spin the pullies by hand and verify the bearings are not 'wobbly'.

T-stew · 2025-10-07T06:42:34-0400

Thanks Bruce. So I took a closer look after work last night. While the pulley spins without any roughness or wobble if I really push it like perpendicularly I can get a little bit of deflection back and forth. I'll plan on replacing the pulley... maybe the whole assembly since its so rusty. I don't think I mentioned but this car has about 230k on it, all in the rust belt. I suppose stock pulleys failing at this point is par for the course. I could see if I can clean it all up, it is removed from the car since when the belt came off it wedged itself behind the tensioner. I was on my way to work and the easiest way to get the belt unjammed was to remove the whole tensioner.

BruceP · 2025-10-07T10:00:47-0400

The tensioner-pullies are a fairly common component. The very same pully with bearing is used across pretty much all Asian vehicles.
HENCE: They are readily-available for reasonable cost. The last time I looked on Amazon, the pully-with-bearing was under $20. Personally, I never buy the cheapest parts... I look for Japanese or German brand-name bearings [American manufactured bearings are with the unicorns 😢 ]

T-stew · 2025-10-08T10:12:19-0400

Yep, I usually get Subaru parts, if not that then the best parts NAPA can get since there is one local here and I get a fleet discount that usually brings the cost of the premium part to what the economy part cost. Anyhow the pulley has plenty of availability but the bracket is NLA from Subaru. I did find the whole assembly in good shape on ebay so going to try that. Meanwhile I need to patch the hole the belt put in the timing cover when it came off. Probably should pull it all off to make sure rain and crap hasn't gotten inside. That's going to be a pain. I just did the timing belt last year so hopefully the bolts aren't stuck yet. I snapped a good handful of them last year getting that sucker off.

2006 - X 5MT - A/C belt keeps coming off?

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