W220 squealing noise

[design guru]

My car has been running fine but a few weeks back I was getting a squealing noise now and then when I accelerated, recently the sound has been more constant and when pull away or rev the car whilst driving it gets louder but some times it just stops making the noise whilst driving along and then all of a sudden it starts up again. When idle it does not make a sound but if I rev the car in park or neutral it makes the squealing noise. I have changed the belt and looking at the old bet it showed no signs of damage or wear.

I used a stethoscope to pin point the noise but it almost sounds like it from the rear of the turbo, my initial thought was the water pump as it loses 2l of water every 2 weeks but the wheels on the front of the engine all look pretty stable. the sound is almost coming from the CAT behind the turbo.

I am hoping to get a garage to have a quick look to see if they can identify the problem but hopefully someone may have had a similar problem and maybe direct me to a possible area to check. I will need to do a pressure test to find the leak in the cooling system.

W220 2001 S320cdi - 235,000miles

 

[slade1]

Alternator?

 

[ioweddie]

fan belt slip

 

[Deletedmember130310]

I would be more worried about the water loss.

 

[OJLane]

Could it be the Alternator pulley? made an awful noise when that went on my old OM612. I think the alternator on these may be water cooled, probably not where the leak is but maybe worth checking...

 

[design guru]

I few months back the alternator pulley wheel did come off after the bearings in the wheel went and because the alternator still spun by hand the recovery driver mentioned you could get a new pulley and put it on as the alternator was not seized, I did that and it has been fine for 6 months but I will remove the belt again and check the pulley is not freely moving from the alternator spindle. Possibly the alternator is on its way out, He mentioned it looks like the original so with 230k+ on the clock maybe its nearing the end

 

[design guru]

Well, I had the AA out to check the sound and possibly identify the noise and he confirmed it was coming from the back of the engine and said it was possibly the turbo or the exhaust. it was something that needed to be investigated further. Had a recon turbo fitted back in 2012 when I got the car. I'd say it was the turbo as it makes the sound when I apply the accelerator, but sometimes it starts making the sound when I am coasting down a hill without pressing the accelerator. If it was the exhaust it would make the sound constantly, starting to think it could possibly be a blocked CAT? Hopefully an exhaust centre can give a diagnosis.

 

[design guru]

I removed the air filter today and did a complete oil change and service. I thought the oil was not getting to the turbo and that was the cause of the noise, a dry running turbo. After removing all the parts the turbo was spinning fine and made no noise, I had a good look at all the parts and no leaks or splits in the pipes. It sounds like its either the CAT is blocked or exhast has a hole so I emptied a bottle of Cataclean and hopefully it will clear it out a bit.

Thinking about it this began shortly after replacing the accelerator pedal as the EPC light was appearing, the replaced pedal is second hand but would it cause the car to make this sound? I have the old pedal so I may just switch them over and hear if the sound goes away, seems doubtfull but for the sake of 10 minutes its worth a shot.

 

[AntMB]

fan belt slip

The fan's electric, not belt driven.

 

[MWCLS]

Probably referring to the serpentine belt.

 

[Stevie777]

Strange one this, not sure what it could be apart from belt related - please let us all know how you go on.

 

[design guru]

Update. well the sound is still there but seems to come and go when it feels like. Strangely its not losing water, not sure what happened but all of a sudden it just stopped losing water????
The whistling sound is still there but now I get exhaust fumes when I open the windows whilst driving, also the whistle happens when I am coasting the car without acceleration down a hill. I have seen forums about the clamp between the turbo and cat being the cause so I am going to have a look at that.

I recently changed a leaking injector seal as it was leaking quite bad but that was a few months back and I assumed the fuel smell was just the hot engine burning off and debris left over but this is quite strong and on occasions you can almost taste it like a charcoal taste.

 

[dexross]

Update. well the sound is still there but seems to come and go when it feels like. Strangely its not losing water, not sure what happened but all of a sudden it just stopped losing water????
The whistling sound is still there but now I get exhaust fumes when I open the windows whilst driving, also the whistle happens when I am coasting the car without acceleration down a hill. I have seen forums about the clamp between the turbo and cat being the cause so I am going to have a look at that.

I recently changed a leaking injector seal as it was leaking quite bad but that was a few months back and I assumed the fuel smell was just the hot engine burning off and debris left over but this is quite strong and on occasions you can almost taste it like a charcoal taste.

How did you resolve this buddy, I have the exact same symptoms

 

[design guru]

How did you resolve this buddy, I have the exact same symptom

I never really resolved the issue, but a few months later the alternator started draining the battery so I am guessing the alternator is the culprit. The car has been sorn since august, a few months after posting this.