[jagjitnatt]

Hi All,

I bought a used 2011 335i (82k miles), but it starting making very loud chirping sounds within a week, when I got it inspected, turned out to be a wobbling crank pulley.

The garage replaced it with a new crank pulley and belt. All was fine for a month. Now again I can hear chirping sounds from the engine, not as loud as earlier but its audible on idle and under 1000 rpm, and pretty loud when I switch on the ac. I checked the pulley and it is wobbling, its not too bad, but the wobble is there.

Can any one help me understand why a new pulley could be wobbling?
Its like 4 chirps a second

[robthewrench]

How many miles on the 'newer' belt and tensioner? It may be that the 2nd pulley has been wobbling since it was installed, but now the belt has stretched a little, or the tensioner is getting weaker, or both.

Before anything else, I'd throw a new belt on there and see if the sound continues. Cheapest way to start looking for a solution.

If this does not fix the issue and you do have a wobbling crank pulley, ECS suggests that the rubber in the damper on the pulley has started to dry out:

[I]The vibration damper, sometimes referred to as the crankshaft pulley, is a crucial part of the engine in your BMW. Not only does this pulley supply power to all of the belt driven accessories on the engine, it also absorbs the shock of the engine while it is running to help give your engine a smooth, quiet idle.
If you vibration damper is failing, it will usually present itself in the form of a squealing noise that sounds like a slipping belt. This is an indication that the rubber ring inside of the vibration damper has dried out and cracked, causing the pulley to slip.
If your vibration damper has seen better days, it must be replaced in order to keep your engine running properly, and all of you accessories functional.[I]

[juld0zer]

Do this test for me. When you hear the chirping noise, unscrew the engine oil cap and slowly cock it open. Does the noise stop/decrease?

[jagjitnatt]

Originally Posted by robthewrench

How many miles on the 'newer' belt and tensioner? It may be that the 2nd pulley has been wobbling since it was installed, but now the belt has stretched a little, or the tensioner is getting weaker, or both.

Before anything else, I'd throw a new belt on there and see if the sound continues. Cheapest way to start looking for a solution.

If this does not fix the issue and you do have a wobbling crank pulley, ECS suggests that the rubber in the damper on the pulley has started to dry out:

[I]The vibration damper, sometimes referred to as the crankshaft pulley, is a crucial part of the engine in your BMW. Not only does this pulley supply power to all of the belt driven accessories on the engine, it also absorbs the shock of the engine while it is running to help give your engine a smooth, quiet idle.
If you vibration damper is failing, it will usually present itself in the form of a squealing noise that sounds like a slipping belt. This is an indication that the rubber ring inside of the vibration damper has dried out and cracked, causing the pulley to slip.
If your vibration damper has seen better days, it must be replaced in order to keep your engine running properly, and all of you accessories functional.[I]

Less than 1000 miles on the new belt and crank pulley.
Is the vibration damper part of the pulley? I think the harmonic Balancer and the pulley were one piece, so they were replaced together.

I think I can try a new belt though

[jagjitnatt]

Originally Posted by juld0zer

Do this test for me. When you hear the chirping noise, unscrew the engine oil cap and slowly cock it open. Does the noise stop/decrease?

I will do the test today and post the results

[jagjitnatt]

UPDATE:

I opened the oil cap while running, no change to the noise.
Then I tried to spray some water on the belt, the noise goes away instantly.

The car has been in the shop, they diagnosed it with a faulty tensioner, we replaced the tensioner as well as the 2 idler pulleys, no change whatsoever.

Now they think its the Harmonic Balancer because they can see the slight wobble, and according to them they checked using a stethoscope and the noise is coming from the harmonic balancer.

Tensioner is new
Belt is 1000 miles old
Harmonic Balancer(crank pulley) is 1000 miles old
Idler pulleys are new too.

I think the noise is coming from the area between harmonic balancer and the idler pulley, and I can see the pulley wobbling slightly.

Should I get the harmonic balancer replaced? This thing is killing me

A video for sample -

[BashShah]

did the belt ever shread on this car?
before you bought it?

do you have service history?

[jagjitnatt]

Originally Posted by DarkNemesis

did the belt ever shread on this car?
before you bought it?

do you have service history?

Unfortunately I don't have service history. Is it something I can find out by calling BMW?

[BashShah]

I think it time to take it to the dealer.
let them diagnose it.....this noise would sure bug me enough not to drive the car.

But as you turn your car in, ask to speak directly to the shop foreman, and sit down with him to advise what has been done before had so not to repeat the same things again.

I hate going to stealerships, but there are times that indy's just can't help.

My 2 cents, stop waste time in diagnosing yourself.
get it fixed, and enjoy it.

PS: I spent 2.5 months trying to diagnose a O2 sensor issue.
only the dealer stated within an hour....it's the DME.
they had proper diagnostic scanner to connect between dme to vehicle harness, and and told me PIN 11 on DME to O2 Sensor resister was bad.

also, the squeak is clearly Rubber to something...
could be belt to wheel.
but it could be Crank shaft seal to center rod.......hopefully not.

[juld0zer]

Pretty much all N55 engines have what appears to be a wobbly crank pulley/harmonic balancer (it's the same item). It's not as bad as N20 pulleys though.

Was the replacement pulley a genuine BMW pulley? Genuine belt? Genuine tensioner?

Inspect all the ribbed pulleys on the accessories (alternator, AC compressor, power steering pump). You will need to slacken the belt to rotate them by hand to inspect for melted rubber in the grooves. Also inspect the rib profile on the pulleys as a new belt will sit differently on worn pulleys. Melted rubber from a disintegrating or slipping belt will accumulate in the pulley grooves. This will elevate a belt and cause slipping.

Is it a manual or automatic/DCT 335i?

[jagjitnatt]

Originally Posted by juld0zer

Pretty much all N55 engines have what appears to be a wobbly crank pulley/harmonic balancer (it's the same item). It's not as bad as N20 pulleys though.

Was the replacement pulley a genuine BMW pulley? Genuine belt? Genuine tensioner?

Inspect all the ribbed pulleys on the accessories (alternator, AC compressor, power steering pump). You will need to slacken the belt to rotate them by hand to inspect for melted rubber in the grooves. Also inspect the rib profile on the pulleys as a new belt will sit differently on worn pulleys. Melted rubber from a disintegrating or slipping belt will accumulate in the pulley grooves. This will elevate a belt and cause slipping.

Is it a manual or automatic/DCT 335i?

The replacement pulley was genuine BMW, the belt was a continental belt(OEM). The tensioner and idler pulleys were OEM(INA) too.

I did check the alternator pulley a few days back and belt doesn't seem to be melting, its clean. I do see a lot of gunk on the front of the engine, its almost a millimeter thick. Could it be the oil from OFHG?

It is an automatic. Also when the harmonic balancer was changed along with the belt (in april), the noise had completely gone, but its coming back and getting louder over time.

Also when I start the car, it is very faint, but within 3-5 min, it gets loud. Switching on the AC makes it worse and spraying water on the belt makes it quiet again.

I recently moved to Lafayette, LA, I don't know good indys here, I am preparing myself to pay a visit to the dealer now

[BashShah]

Take it in, and tell them, 2 hours max......figure it out.

Good luck.

[jagjitnatt]

Originally Posted by DarkNemesis

Take it in, and tell them, 2 hours max......figure it out.

Good luck.

Have an appointment on monday.....Fingers crossed

[jagjitnatt]

The guys spent a few hours diagnosing but couldn't figure out what's causing the noise. They replaced the belt which has fixed the noise. But I get a feeling, as the belt gets older, the noise will come back. Let's see how it goes.

[BashShah]

I am surprised.
so replacing the belt .....again....solved it.
but that belt replacement period was short......
post back if Noise returns.
also ask dealer......did they LUBE anything else?....speak to the tech directly.
do it before he forgets.

[jagjitnatt]

Originally Posted by DarkNemesis

I am surprised.
so replacing the belt .....again....solved it.
but that belt replacement period was short......
post back if Noise returns.
also ask dealer......did they LUBE anything else?....speak to the tech directly.
do it before he forgets.

They didn't lube anything. I spent some time with them myself, explained everything I tried earlier. The wobble as per them is normal, and within specs.
They drove the car around for some time after the belt change, the noise didn't come back. It will take another 500-800 miles for it to come back I think.

If it does come back, I'm going back to them, or the shop that changed the harmonic balanced. They have a 3 year warranty on the part. And if nothing works, maybe I'll put a dayco belt on it myself.

[BashShah]

I think it's the Harmonic Balancer is Faulty.

you have changed like 3 Belts.
noise comes back.

I realize that initial after belt change the noise goes away, but it come back on the 2nd or third Gas fill.
the ONLY component not messed with is the Harmonic Balancer.

The Balancing weights are glued on...... a wobble is not normal.
I think the weights are not glued properly.

[jagjitnatt]

Originally Posted by DarkNemesis

I think it's the Harmonic Balancer is Faulty.

you have changed like 3 Belts.
noise comes back.

I realize that initial after belt change the noise goes away, but it come back on the 2nd or third Gas fill.
the ONLY component not messed with is the Harmonic Balancer.

The Balancing weights are glued on...... a wobble is not normal.
I think the weights are not glued properly.

The harmonic balancer is only 3 months old. It's under warranty. If the noise comes back, I will get it replaced again.

[Hannibal4444]

Check for oil leak. The main problem for the chirp, from many people including myself, has been caused by oil leaking onto the belt. Closely inspect the notorious OFHG for leaks.

[sicknick530]

I’m battling with this same exact issue, with the same 2011 335i. What was the outcome for you? Did you ever diagnose the issue? I’d love to know. This has been whopping me for 3 months. 2 harmonic balancers & almost 2k later. I’m terrified of eating my belt. Please help!!

[Seanjohn004]

Going through this right now

[juld0zer]

Bent crank? I'd say one of the grooved pulleys has a wobbly bearing which chews the ribs of the belt, causing it to slip. Could even be the tensioner itself - the arm may have excessive play at its pivot. That is if there is no oil or coolant leaking onto the belt and pulleys