Strange metallic grinding noise when engine in idle: 2006 997 C4
#1
Strange metallic grinding noise when engine in idle: 2006 997 C4
I have a 2006 C4 with 49K miles and from a cold start, I began hearing this intermittent grinding noise on top of the regular engine hum during idle. This strange sound would go in and out just like how a locomotive would sound with intermittent whinning noise (which sounds very painful to me by the way). I took off the Air intake assembly to inspect the serpentine belt and the various pulleys, bearings and snubbers. They all seemed fine. I've attached a link to the video so you all can see.
thanks
thanks
#5
Agree- sounds like a bad pulley driven item. Maybe the idler pulley. Did you record in stereo? it sounds almost like it's coming from the left.
You can take the belt off an spin each one to test. Or you can use a piece of 1/2" rubber hose like a stethescope. Or you can even take a long screwdriver and use the handle against your ear and rest the tip against each pulley driven item (start by putting it against the alternator etc). Sounds crazy but it works well.
You can take the belt off an spin each one to test. Or you can use a piece of 1/2" rubber hose like a stethescope. Or you can even take a long screwdriver and use the handle against your ear and rest the tip against each pulley driven item (start by putting it against the alternator etc). Sounds crazy but it works well.
#6
Race Director
Sounds like an accessory drive is noisy. My WAG would be the water pump.
Before you do anything you might want to drop the oil filter housing and dump the oil and element into a *clean* drain pan. What you see or don't see determines what you do next.
If the oil is clean of any debris one 'trick' is to carefully note the belt's routing (take a pic!) and its direction of rotation (pic!) and then remove the belt. You can start the engine and run it a while like this.
If the noise is absent then almost certainly it is an accessory drive (or idler/tensioner roller bearing) that is making the noise.
If the noise is still present, you're done. Take the car to a qualified shop for diagnosis.
Check the belt. My experience when a water pump got a bit noisy was the belt developed a sharp inside edge due to excessive bearing play at the water pump which allowed teh belt to mistrack and rub against the side of the grooved water pump pulley.
With the belt removed you can test each accessory drive for any signs of play. There may not be much but you'll have probably one 'bad' one and the rest good and by comparing the play of each if there's one with any play that's the suspect drive.
Check the idler roller and tensioner bearings for excessive play or roughness or signs of seal degradation.
Sincerely,
Macster.
Before you do anything you might want to drop the oil filter housing and dump the oil and element into a *clean* drain pan. What you see or don't see determines what you do next.
If the oil is clean of any debris one 'trick' is to carefully note the belt's routing (take a pic!) and its direction of rotation (pic!) and then remove the belt. You can start the engine and run it a while like this.
If the noise is absent then almost certainly it is an accessory drive (or idler/tensioner roller bearing) that is making the noise.
If the noise is still present, you're done. Take the car to a qualified shop for diagnosis.
Check the belt. My experience when a water pump got a bit noisy was the belt developed a sharp inside edge due to excessive bearing play at the water pump which allowed teh belt to mistrack and rub against the side of the grooved water pump pulley.
With the belt removed you can test each accessory drive for any signs of play. There may not be much but you'll have probably one 'bad' one and the rest good and by comparing the play of each if there's one with any play that's the suspect drive.
Check the idler roller and tensioner bearings for excessive play or roughness or signs of seal degradation.
Sincerely,
Macster.
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#9
Rennlist Member
thanks in advance.
#11
Usually when they'll uni directional they have the little arrows printed on the belt. i can't remember if this one is uni or bidirectional but you can just check the one on the car. it takes a long time for the markings to wear off. I'm pretty certain that it's bi-directional.
#12
Race Director
i dont want to hijack the thread, but if i may please ask a quick (stupid ) question: obviously the routing is paramount, but is the belt's rotation uni-directional?? i changed mine a few months ago but didnt pay attn to the direction nor can i find any directional markings on the old one.
thanks in advance.
thanks in advance.
Sincerely,
Macster.
#15
didn't get a chance to update you guys on this matter....didn't get back to it till last night but here are my observations:
- so i ran the engine for a few moments without the belt and the strange noise was not present which was great so it must be one of the accessories as all of you mentioned.
- next I spun each pulley / idler / accessory and nothing popped out of the ordinary in terms of resisting rotation or excessive play/wobbling.
- so i reconnected the belt and started the engine again to diagnose further. Took a really bright lamp and shown it on the fully exposed rotating belt pulley/idlers etc... as the engine was running. What i noticed is that there was a slight wobble (the kind only you would notice if you were to shine intense light on) on the water pump pulley and it synched with this aweful sound. So I went underneath placed my ear relatively near the pump housing which is visually accessible directly beneath the car. The noise definitely was coming from it because when i touched the housing (that's because I didnt have a stethoscope) I felt this vibrating sensation that again, synched up with the aweful noise. I also tried resting the tip of a long screwdriver and placing the back of the handle against my ear and confirmed this grinding vibration. Also tried this trick on the rest of the accessories (alternator, compressor, idler, tensioner..etc...) what I heard were slight and smooth vibrations - 10 folds less intense than with the water pump.
So I ordered a new pump arriving tomorrow morning and a video I found to perform the replacement...stay tuned..
- so i ran the engine for a few moments without the belt and the strange noise was not present which was great so it must be one of the accessories as all of you mentioned.
- next I spun each pulley / idler / accessory and nothing popped out of the ordinary in terms of resisting rotation or excessive play/wobbling.
- so i reconnected the belt and started the engine again to diagnose further. Took a really bright lamp and shown it on the fully exposed rotating belt pulley/idlers etc... as the engine was running. What i noticed is that there was a slight wobble (the kind only you would notice if you were to shine intense light on) on the water pump pulley and it synched with this aweful sound. So I went underneath placed my ear relatively near the pump housing which is visually accessible directly beneath the car. The noise definitely was coming from it because when i touched the housing (that's because I didnt have a stethoscope) I felt this vibrating sensation that again, synched up with the aweful noise. I also tried resting the tip of a long screwdriver and placing the back of the handle against my ear and confirmed this grinding vibration. Also tried this trick on the rest of the accessories (alternator, compressor, idler, tensioner..etc...) what I heard were slight and smooth vibrations - 10 folds less intense than with the water pump.
So I ordered a new pump arriving tomorrow morning and a video I found to perform the replacement...stay tuned..