[Sapote]

Yesterday my new 2003 325iT suddently sounded like a cricket, high frequency noise under the hood. Today I removed both belts and noise gone, hoping a pulley bearing was bad. All pulley bearings were smooth with new greased I replaced few weeks ago. Replaced with new WP last week; alternator and steering pump were also smooth noise less. I thought might be the new WP shaft seal needed some times to be quiet. I installed everything back and the noise came back as expected. I will try to add the sound file.

I think many E46 also have the same issue and noise but owners don't know or just get used to it.

Noise:

What else should I look?

Fixed:

 

[BigBopper]

Yesterday my new 2003 325iT suddently sounded like a cricket, high frequency noise under the hood. Today I removed both belts and noise gone, hoping a pulley bearing was bad. All pulley bearings were smooth with new greased I replaced few weeks ago. Replaced with new WP last week; alternator and steering pump were also smooth noise less. I thought might be the new WP shaft seal needed some times to be quiet. I installed everything back and the noise came back as expected. I will try to add the sound file.

I think many E46 also have the same issue and noise but owners don't know or just get used to it.

Noise:

What else should I look?





























































Fixed:

Remove the belts and spin the pulleys. There should be no noise when you spin the pulleys if your pulley bearings are ok. If there is noise then replace the pulley.

 

[MrMCar]

The noise I heard (good soundbite BTW) is a rubber to pulley interface noise. When I encounter such a belt noise (a pet peeve of mine) it's almost always some sort of contamination onto the belt. Sometimes as simple as water all the way up to coolant and/or a P/S fluid.
Insofar as the water based noise, most often a couple of heat cycles take care of it.
Rinsing the pulleys and thorough drying before any belt installation usually mitigate a maleficent drop of any unwanted fluid.
I have found that a couple of small dabs of dielectric grease applied to the ribbed portion of the belts (engine off) then starting usually takes care of a noise w/o issue.
Good luck.

 

[Sapote]

The noise I heard (good soundbite BTW) is a rubber to pulley interface noise. When I encounter such a belt noise (a pet peeve of mine) it's almost always some sort of contamination onto the belt. Sometimes as simple as water all the way up to coolant and/or a P/S fluid.
Insofar as the water based noise, most often a couple of heat cycles take care of it.
Rinsing the pulleys and thorough drying before any belt installation usually mitigate a maleficent drop of any unwanted fluid.
I have found that a couple of small dabs of dielectric grease applied to the ribbed portion of the belts (engine off) then starting usually takes care of a noise w/o issue.
Good luck.

You're right on about the belt noise. I used the stethoscope on WP, idler, tensioner, alternator, AC compressor and tensioner, and all running smooth like a cat puzzing. I thought the new WP rubber seal, but it was deep inside and in coolant so how could it sang so loud. I almost gave up hoping for a miracle that it will disappear soon. I just stood there staring at the parts, then I remember the famous firecracker noise generated by the alternator V belt on my '74 Citroen SM when the pulley was not perfectly aligned -- the belt tried to climb up the pulley and then snap back down making a loud firecracker. I used a long straight edge checking from the crank pulley face to WP, thinking the new WP pulley was a little too forward causing the belt to climb or rub, but it was perfectly level. Then from crank pulley to tensioner. Bingo! The belt was about 2mm hung over the tensioner pulley edge! For some reasons, the tensioner pulley shaft is not square to the engine. My first thought was might be the bearing had too much play and cocked under the belt tension, but it was perfect with only tiny clearance as all ball bearings. I removed the tensioner and cleaned up the OFH mounting surface really good, but this still didn't fix the issue (I swapped out the stock hydraulic for a good working mechanical tensioner I saved from my dead 2000 323iT). Could the tensioner pivot bushing worn down and cocked the pulley? I studied it carefully and didn't see any indication of a worn bushing -- the whole rotating thing was parallel with the mounting bracket on all sides. I ran out of ideas, and so I had to shim the mounting bracket for now and will try with a new mechanical tensioner later. I cut the shims out of a new grease aluminum cap. This worked and the engine was running like a cat puzzing as in the 2nd video sound clip.

I think people should use a straight edge and check your belt: rest the straight edge on the crank pulley and sweep it around to WP, tensioner pulley, idle, alternator, and steering pump. The belt should be 2mm below the straight to all component. If not this cause the belt edge to rub against the pulley and it sounds like a cricket or an engine about to explode.

 

[Alex323Ci]

Ah, will try this as it might be reason for my new squeak (only after new belt installed). I thought it was accentuating a failing pulley bearing or mechanical tensioner.

 

[Sapote]

I bet all the E46 out there have some belt rubbing on WP pulley edge as the components aged and worn, to some degrees. This would create a high pitch noise superimpose on top of the normal nice engine hum. To have a nice sound as a brand new engine out off factory floor, one should check the belt alignment with a straight edge and shim the cocked pulley base as needed.

 

[BiH55]

Mine sounds like that after it rains

 

[MrMCar]

You're right on about the belt noise. I used the stethoscope on WP, idler, tensioner, alternator, AC compressor and tensioner, and all running smooth like a cat puzzing. I thought the new WP rubber seal, but it was deep inside and in coolant so how could it sang so loud. I almost gave up hoping for a miracle that it will disappear soon. I just stood there staring at the parts, then I remember the famous firecracker noise generated by the alternator V belt on my '74 Citroen SM when the pulley was not perfectly aligned -- the belt tried to climb up the pulley and then snap back down making a loud firecracker. I used a long straight edge checking from the crank pulley face to WP, thinking the new WP pulley was a little too forward causing the belt to climb or rub, but it was perfectly level. Then from crank pulley to tensioner. Bingo! The belt was about 2mm hung over the tensioner pulley edge! For some reasons, the tensioner pulley shaft is not square to the engine. My first thought was might be the bearing had too much play and cocked under the belt tension, but it was perfect with only tiny clearance as all ball bearings. I removed the tensioner and cleaned up the OFH mounting surface really good, but this still didn't fix the issue (I swapped out the stock hydraulic for a good working mechanical tensioner I saved from my dead 2000 323iT). Could the tensioner pivot bushing worn down and cocked the pulley? I studied it carefully and didn't see any indication of a worn bushing -- the whole rotating thing was parallel with the mounting bracket on all sides. I ran out of ideas, and so I had to shim the mounting bracket for now and will try with a new mechanical tensioner later. I cut the shims out of a new grease aluminum cap. This worked and the engine was running like a cat puzzing as in the 2nd video sound clip.

I think people should use a straight edge and check your belt: rest the straight edge on the crank pulley and sweep it around to WP, tensioner pulley, idle, alternator, and steering pump. The belt should be 2mm below the straight to all component. If not this cause the belt edge to rub against the pulley and it sounds like a cricket or an engine about to explode.

Is/Was yours missing the mudgard? # 11281730532? (#20)

RealOEM.com - Online BMW Parts Catalog

BMW parts 3' E46 330i Belt Drive Water Pump/Alternator

www.realoem.com

 

[Alex323Ci]

Protection Ring

Seals the back side of the hydraulic alternator belt tensioner roller from debris

www.ecstuning.com

interesting, never knew it was called that Don.
your daily experience would know, but i can’t think of any way that piece isn’t there unless removed during a bearing pulley swap?

 

[Sapote]

Is/Was yours missing the mudgard? # 11281730532? (#20)

RealOEM.com - Online BMW Parts Catalog

BMW parts 3' E46 330i Belt Drive Water Pump/Alternator

www.realoem.com

Interesting that you pointed out this dust shield, which is not used on the mechanical tensioner. In my case, it's a mechanical tensioner which replaced the hydraulic one.

 

[Sapote]

I think now I appreciate more of the hydraulic tensioner over the mechanical one after this event.

The hydraulic has a long and stable #5 roller bearings to pivot the pulley swing arm #4. Its base plate #2 is mounted to the OFH by 3 bolts as compared to the mechanical only 2 bolts. I don't know what is used in the mechanical tensioner to pivot the swing arm but I doubt it has the same #5 roller bearings. Therefore the hydraulic has a more stable and squared pulley arm than the mechanical unit, resulting a better belt alignment on the hydraulic.

Due to only 2 points mounting base plate and questionable pivot design, the mechanical tensioner might not have its pulley perfectly parallel to the WP pulley, leading to some amount of cricket chirping.

Don, in my case it's not that the tensioner pulley sit lower than the WP pulley, but the problem is the pulley not parallel to the WP pulley. I shimmed it to have both in parallel so the belt don't try to run off. The more all pulleys are in parallel the less chirping noise it creates.

 

[Sapote]

Ideally the tensioner should be located at the idler and vice versa. Why?
Currently the tensioner is pulled by 2x the belt tension, while the idler is pulled less than the belt tension due to the geometry of the belt at these pulleys. Sitting on the tennis net cord will break it while sitting on a 2-string swing with the same cord will not. The tensioner is like the swing. Therefore at the currently idler location, the tensioner with swing arm will not be subjected under high pulling force and it needs less spring load force and less wear on the pivot bushings or bearings. Why BMW didn't do this?

BTW, the chain tensioner located at the right place as compared to the belt tensioner.

 

[MrMCar]

An effect of "Must Have" vs: Packaging.

 

[Alex323Ci]

I recall BMW info somewhere stating the hydraulic tensioner was designed to alleviate the pulses of the engine belt.

 

[Sapote]

I recall BMW info somewhere stating the hydraulic tensioner was designed to alleviate the pulses of the engine belt.

This is correct but this has no relationship to belt misalignment that caused the belt to climb off and the noise.

Hydraulic has more damping action than mechanical unit. It help to slow down the pulley oscillation frequency during engine running.

 

[Alex323Ci]

Yes I know that.

 

[getty150]

You're right on about the belt noise. I used the stethoscope on WP, idler, tensioner, alternator, AC compressor and tensioner, and all running smooth like a cat puzzing. I thought the new WP rubber seal, but it was deep inside and in coolant so how could it sang so loud. I almost gave up hoping for a miracle that it will disappear soon. I just stood there staring at the parts, then I remember the famous firecracker noise generated by the alternator V belt on my '74 Citroen SM when the pulley was not perfectly aligned -- the belt tried to climb up the pulley and then snap back down making a loud firecracker. I used a long straight edge checking from the crank pulley face to WP, thinking the new WP pulley was a little too forward causing the belt to climb or rub, but it was perfectly level. Then from crank pulley to tensioner. Bingo! The belt was about 2mm hung over the tensioner pulley edge! For some reasons, the tensioner pulley shaft is not square to the engine. My first thought was might be the bearing had too much play and cocked under the belt tension, but it was perfect with only tiny clearance as all ball bearings. I removed the tensioner and cleaned up the OFH mounting surface really good, but this still didn't fix the issue (I swapped out the stock hydraulic for a good working mechanical tensioner I saved from my dead 2000 323iT). Could the tensioner pivot bushing worn down and cocked the pulley? I studied it carefully and didn't see any indication of a worn bushing -- the whole rotating thing was parallel with the mounting bracket on all sides. I ran out of ideas, and so I had to shim the mounting bracket for now and will try with a new mechanical tensioner later. I cut the shims out of a new grease aluminum cap. This worked and the engine was running like a cat puzzing as in the 2nd video sound clip.

I think people should use a straight edge and check your belt: rest the straight edge on the crank pulley and sweep it around to WP, tensioner pulley, idle, alternator, and steering pump. The belt should be 2mm below the straight to all component. If not this cause the belt edge to rub against the pulley and it sounds like a cricket or an engine about to explode.

Hell! I'm sold...

Sent from my SM-J727T using Tapatalk

 

[MrMCar]

I bet all the E46 out there have some belt rubbing on WP pulley edge as the components aged and worn, to some degrees. This would create a high pitch noise superimpose on top of the normal nice engine hum. To have a nice sound as a brand new engine out off factory floor, one should check the belt alignment with a straight edge and shim the cocked pulley base as needed.

I follow you (intentional pun) but don't: The ridges (6 of them in this case, as the belt is a 6PK designation) dictate where the belt runs along it's circuitous route. The belt leaves the crank pulley and next up is the water pump then across to the alternator, then the P/S pump. If all of these items with 6 groves in them are in perfect alignment the belt will run straight and true across these, which dictate the parallelism of the belt.

The other "Rollers" be they attached to a deflection and/or tensioner mechanism are bereft of grooves and end stop edges. Should one or more of these secondary rollers be out of alignment, the belt would simply be "running" outside the nominal area. Be it towards the inside or outside. Usually the later. These rollers bereft of guiding vanes and outer ridges do to deflect the belt into any sort of alignment. That is why we often see the last mm or two of the belt start to hang off the edge, rather than be in full contact with the roller and a mm or two of roller exposed.
(This becomes especially important for those that own cars with the family of N52/N54 & N55 engines. These are mechanical tensioners ((Spring type)) and have a tendency to cock to one side as they age. The belt migrates outward and eventually slips off and goes behind the harmonic balancer and winds it's way inside the engine. A very bad situation that happens often. Head's up guys & gals.) Read up on BMW belt ingestion if you care to?

Not having the car in my shop and not performing the work (your shimming is commendable!) I'd offhand think that the noise was from the belt edge where it was hanging over the tensioner roller and not the pump?

Citroen SM, you are a glutton for punishment. Albeit one of the smoothest rides ever. Did your articulating headlamps work?

 

[Sapote]

Citroen SM, you are a glutton for punishment. Albeit one of the smoothest rides ever. Did your articulating headlamps work?

Don, I will have a longer reply to you, but quickly on the SM headlights.

The US version is going to be converted to 6 -light Europe factory style. I had the whole Europe front nose shipped from France 15 months ago, and searched bought all those square headlights. Hydraulic control turning and leveling back in 1970, ahead of anything back then.

 

[Sapote]

The other "Rollers" be they attached to a deflection and/or tensioner mechanism are bereft of grooves and end stop edges. Should one or more of these secondary rollers be out of alignment, the belt would simply be "running" outside the nominal area. Be it towards the inside or outside. Usually the later. These rollers bereft of guiding vanes and outer ridges do to deflect the belt into any sort of alignment. That is why we often see the last mm or two of the belt start to hang off the edge, rather than be in full contact with the roller and a mm or two of roller exposed.
(This becomes especially important for those that own cars with the family of N52/N54 & N55 engines. These are mechanical tensioners ((Spring type)) and have a tendency to cock to one side as they age. The belt migrates outward and eventually slips off and goes behind the harmonic balancer and winds it's way inside the engine. A very bad situation that happens often. Head's up guys & gals.) Read up on BMW belt ingestion if you care to?

Not having the car in my shop and not performing the work (your shimming is commendable!) I'd offhand think that the noise was from the belt edge where it was hanging over the tensioner roller and not the pump?

Citroen SM, you are a glutton for punishment. Albeit one of the smoothest rides ever. Did your articulating headlamps work?

As I said all the pulleys were in parallel except the tensioner. As you said the tensioner and idler pulleys run on the smooth back side of the belt and so there is no grooves or guards on these pulleys. Therefore if the tensioner pulley is slightly out of parallel with the WP pulley then the belt wants to run off the tensioner, but saved by the WP front guard. The guard kept the belt from running off but it also rubbed against the belt causing the chirping noise.

"That is why we often see the last mm or two of the belt start to hang off the edge"
This condition for sure had the belt rubbing the WP front guard and it should create chirping noise until the belt edge worn off.