2006 V70 Alternator belt or pulley making rhythmic grinding

[artgirl]

2006 V70 started making a rhythmic, grinding sound a month or so back. Took it to mechanic who listened and looked at engine. One possibility is the alternator belt or pulley might be making the noise. The small pulley below the larger one, seems to be moving very slightly in and out, pulsing. Anybody have a similar problem or ideas about this?

[jimmy57]

The alternator pulley has a one way clutch and it can be noisy like you describe when the clutch is failing.
The one way clutch lets the alternator not get slowed when the cyclic speed up and slow down occurs due to cylinders on compression stroke slowing nearing TDC and then accelerating after combustion starts. When the engine slows the alternator rotational inertia will keep it spinning while the one way clutch releases on crank slowing. This keeps the belt from taking higher stress and making noise.
The pulley is sold separately from some sources and it takes a hollow spline bit to remove the clutch while a torx or spline bit is used to keep the rotor from turning while clutch is unscrewed.
Or you replace the alternator.

[artgirl]

I have never replaced the belt itself. Could it be that? or is that wishful thinking on my part?

[oragex]

First thing, if it already makes noise, the end is close. End means the pulley will soon seize, breaking the seprentine (alternator) belt. From reading the forums, it's not rare that when the serpentine belt snaps, the timing belt also snaps and ruins the engine. Just a warning..

How many miles on the car?

The alternator pulley is known to seize at higher miles. As mentioned above, the alternator needs to be removed and it's pulley replaced (about $100 in parts). Labour time, perhaps 1h30-2h

The pulley that is shaking is the serpentine belt tensioner. It does shake a little bit indeed (not more that 1/8") and it's also known to seize. Have it checked/replaced ($100+ in parts) while the serpentine belt is out - DON'T use a cheap replacement part for the tensioner. This part is very sensitive and aftermarket ones are known to fail. To replace the tensioner is a 10min. job.

While there, also check the A/C pulley for smooth rolling.

A belt is $20 right now off Ebay (look for Gates). If it has cracks it's time to change it.

[oragex]

Just wanted to mention, the chirping sound is usually caused by smaller pulleys, such as the serpentine tensioner pulley. However, the timing belt, which is located behind the serpentine belt, inside a plastic cover, also has two small pulleys- a tensioner and a roller. It is important to make sure the noise doesn't come from those timing belt pulleys, which are also known to seize and to bust the engine. Removal of the timing belt covers for inspection should take no more than 10 min.

[draser]

My day just got a whole lot worse. My car had an alternator noise since new (new to me at 50k) and I just thought it was a dry bearing. Makes kinda chirpy noises when cold. Now I learned there's a clutch in there, that it can seize, it's depressing. And too cold in the garage right now, gonna chance it until spring. Ignorance is bliss...

[DGM]

Recently I replaced the voltage regulator on my alternator (V70 2005) and as a precautionary measure installed a new clutch pulley. I bought this tool to remove & install the pulley;

http://www.eeuroparts.com/Parts/9830/Fr ... Tool-8088/

It is of good quality for the price.

[jimmy57]

The clutch needs to be verified as the noise by testing. Take belt off and then grab the alternator pulley. Turn it sharply CW and don't release it. When you hold pulley the alternator should continue to turn a bit CW. If the alternator rotor stops when you hold the pulley then the clutch is faulty.
The alternators with the clutched pulley will be noted by having an internal spline around the hole in the pulley front. The fixed pulleys will have the large nut holding the pulley to alternator rotor.

Prior to the one way clutch, the cyclic belt loading was attempted to be addressed by higher belt tension and dampened tensioner arm. This approach was not altogether successful and not for too long. The clutch feature allows reduced belt tension and get better belt life since the slip that was occurring before is eliminated.
The new way to deal with this that is used on the new Volvo 4 cylinders is to have a sprung crankshaft belt pulley. The spring winds to absorb the short crank accelerations and on the deceleration the spring unwinds to keep rotational velocity changes to a minimum. With this solution no clutched alternator pulley is needed.

[cn90]

There is an easier way to test the clutch.

Since the Alternator Pulley normally spins CCW (think bicycle), leave the belt alone. Instead, use appropriate Torx key and turn the clutch as follows:

- CCW, it should turn freely.
- CW, you should not be able to turn it because the belt is still on and keeps the pulley stationary.

Think bicycle and you will get it...

[oragex]

A small video with the pulley