High pitched noise when cold starting

[Brzerker]

Hi all,

Recently I've noticed a high pitched noise coming from the AC compressor area during cold starts. I'm not sure if it's coming from the high pressure fuel pump or the AC compressor.

Video of sound during cold start
https://streamable.com/e/j8ayq8

Hopefully someone here has an idea what could be the cause.

Thanks!!!!

[Ultramaroon]

It's the belt slipping over your alternator pulley. Get a fresh accessory belt or clean all the tiny pieces of sand stuck in the grooves of your current one.

[Brzerker]

Originally Posted by Ultramaroon

It's the belt slipping over your alternator pulley. Get a fresh accessory belt or clean all the tiny pieces of sand stuck in the grooves of your current one.

Thanks! Will take a look at the belt. Weird thing is the sound goes away when the car warms up.

[blsfrs]

Originally Posted by Brzerker

Thanks! Will take a look at the belt. Weird thing is the sound goes away when the car warms up.

While the belt is off, spin the idler pulleys and check them for free play. A new belt might be a good idea. A belt conditioner product might help the old belt. Sand in your groove can definitely be a problem.

[Tcoat]

Originally Posted by Brzerker

Thanks! Will take a look at the belt. Weird thing is the sound goes away when the car warms up.

As the belt warms up it becomes "softer" and seats better in the pully which makes the noise go away.

[Ultramaroon]

Originally Posted by Brzerker

Thanks! Will take a look at the belt. Weird thing is the sound goes away when the car warms up.

Originally Posted by Tcoat

As the belt warms up it becomes "softer" and seats better in the pully which makes the noise go away.

The sound goes away when the alternator is finished doing most of its work. First the battery dumps a bunch of energy into the starter, then the alternator works hard to dump all that energy back into the battery.

Crank on the headlights, step on the brakes for those lights, and set the cabin blower to high. Does the belt squeak over the alternator pulley then?

Belt dressing is evil. It just ruins the belt.

For some reason on this car, sand does settle into the belt grooves. I'm still on the original and I've cleaned it twice by carefully picking out the grains with a needle.

[RToyo86]

I've got 115,000km on the OEM belt. I'm used to changing these more often on other cars. :Lol:

[Tcoat]

Originally Posted by Ultramaroon

The sound goes away when the alternator is finished doing most of its work. First the battery dumps a bunch of energy into the starter, then the alternator works hard to dump all that energy back into the battery.

Crank on the headlights, step on the brakes for those lights, and set the cabin blower to high. Does the belt squeak over the alternator pulley then?

Belt dressing is evil. It just ruins the belt.

For some reason on this car, sand does settle into the belt grooves. I'm still on the original and I've cleaned it twice by carefully picking out the grains with a needle.

A cold belt will always squeal where a warm one won’t regardless of load.

[Ultramaroon]

Originally Posted by Tcoat

A cold belt will always squeal where a warm one won’t regardless of load.

I agree that cold temperature exacerbates the issue. It is not the main reason the belt slips over an alternator pulley immediately after startup.

Another way to test but might cause a MIL. While it's squealing, disconnect the regulator connector. Won't hurt anything. Alternator immediately becomes an idler pulley.

[humfrz]

Originally Posted by Ultramaroon

...........
Belt dressing is evil. It just ruins the belt.

Says you. But, back in the day, it was very important. As a kid, that was part of my job. Yep, then I would lay grasshoppers on the belt and see if they would jump off before they would reach a pully -

[humfrz]

Originally Posted by Ultramaroon

...........
Belt dressing is evil. It just ruins the belt.

Says you. But, back in the day, it was very important. As a kid, that was part of my job. Yep, then I would lay grasshoppers on the belt and see if they would jump off before they would reach a pulley -

[Ultramaroon]

Originally Posted by humfrz

Says you. But, back in the day, it was very important. As a kid, that was part of my job. Yep, then I would lay grasshoppers on the belt and see if they would jump off before they would reach a pulley -

I had no idea that grasshoppers make a good belt dressing.

[humfrz]

Originally Posted by Ultramaroon

I had no idea that grasshoppers make a good belt dressing.

They didn't - that's the reason my grandpa made me quit doing it. -

[Brzerker]

An update on the issue.

Took the belt off to inspect and found a bigger issue, leaking coolant! I think the belt might have been tainted with coolant which was causing the squeaks. My local mechanic swapped the belt and broken plate, and all seems to be good for now. Car is around 180k km (~110k miles)

btw, does anyone have a name for what this plate is called?