4.8i a/c belt squeaking

[Cyrix2k]

This is driving me crazy. On my '07 4.8i, I have a belt squeak when warm. It chirps a little at idle and squeals past 1k or so RPM. This noise has been present since I bought it and hasn't gotten worse or better as I've driven it during the past year. I figured it was just an idler pulley going bad so I replaced the main belt, a/c belt, the main tensioner, idler, and the a/c tensioner (the manual one). I want to say I spun all the accessories by hand when the belt was off and they seemed fine; the water pump especially looks new although it was replaced prior to my ownership. With all that replaced, it was *still* making the same noise - so I replaced the a/c "clutch" bearing with a new NSK bearing. And it STILL makes the same noise! Any ideas? Is the a/c belt directional (I think I read something about that, but don't recall seeing it mentioned in TIS when newTIS was still up). What should the tension be on the a/c belt? I had it close to what the main belt felt like and I just cranked the tensioner down today. It seems a little quieter but also feels very tight and it's still making noise with revs.

[andrewwynn]

Somebody on xo had the same symptoms very recently. Turned out to be the harmonic balancer. Aka crank pulley.

Apparently those are made from two steel parts with rubber sandwich in the middle. If they start to delaminate, they will chirp/squeak and more when warm than cold.

In my collection of things I have a spare from I think an M62 motor. They are stupid expensive I would be able to sell a lot cheaper if I can find it.

[Cyrix2k]

:-/ Hopefully that's not the case. Do you know if the M62 harmonic balancer fits an X5 N62TU? The part numbers don't appear to cross reference but if it does, I might have an M62TU balancer available locally. I also saw that a lot of people pull the balancer to do the water pump on these engines, I wonder if this one was pulled and just not pressed back into the correct position resulting in an alignment issue?

[andrewwynn]

I was pretty sure there was a pin index on the couple I did. Unless it's close enough to hit something and scrape I doubt a misalllign is causing the squeak.

Look at realoem.com for your car. Find the part and drill down to detail it will show the cars that used the same part. Fun to see some parts that go back into the 70s

[Cyrix2k]

Yeah, realoem only shows the crank pulley as fitting e70 x5s. It must be due to the accessory drive. Would you happen to know the other thread on xo that had a similar issue? I haven't been able to dig up much other than "it's not tensioned enough", there are bad bearings, or the belt is contaminated. The latter is a possibility but I don't think that's it considering it started on the first drive and all the belts are new.

[andrewwynn]

N55 Vibration Damper noise
https://r.tapatalk.com/shareLink/top...ink_source=app

[Cyrix2k]

Thanks, that sounds exactly like mine :-/ I'll have to look at the crank pulley more closely, I didn't think it was wobbling but I also never looked at it too hard when warm.

[andrewwynn]

Similar to suspension joints. They are usually pretty impossible to move by hand there is a ton of force on the crank pulley. I've remove and replace a few and never even knew at the time they were multiple pieces thought were solid steel.

[Cyrix2k]

I just ordered a used one with 64k miles on it. We'll see if that fixes it. I got the X5 all warmed up and looked at the pulley and I think it does have a very slight wobble to it.

Originally Posted by andrewwynn

Similar to suspension joints. They are usually pretty impossible to move by hand there is a ton of force on the crank pulley. I've remove and replace a few and never even knew at the time they were multiple pieces thought were solid steel.

Yeah. I knew some of them were made like this but always thought failure was extremely rare. On older vehicle where the crank position sensor actually reads the crank pulley, the outside of the pulley can slip and throw the reading off.

[andrewwynn]

I'm pretty confident you found the problem. I usually monitor all new threads and can remember which I've joined and that previous one is very recent.