[SOLVED] Underhood Intermittent Screech In Freezing weather

[EddieC]

I recently have has a screech that seems on the left front side of our (5.3) engine (2008 Tahoe) when the weather temperature is 20 degrees and lower.
After a certain rpm, perhaps 2000 to 2500, it goes away but effeminately varies with the rpms and comes back when the revs drop but is mostly gone at idle.
It seems like it might be the PS pump or alternator but on a few tries it's tough to pin down.
There does not seem to be an uncharacteristic odor and the alternator seems to be functioning normally based on the instrument panel gage and the state of the battery. The power steering is functional and there is fluid in the reservoir.
Both drive belt tensioners were replaced with oem last year as were the belts.
Also there are no coolant leaks at the water pump and the temperature gage is running normal.

Any thoughts on which might be more likely to make the screeching noise if failing?

 

[Fless]

Accessory belt idler pulley?

Pull the belts off and see if it still happens, and check pulleys while the belts are off. Don't run it very long without the belts.

 

[OR VietVet]

Belt or idler or tensioner not liking the cold.

 

[Doubeleive]

generally the only things that screech are the idler/tensioner/ac pump, funky serpentine belt or ac belt
that being said the ac pump may screech and/or eventually sound like a tin can full of nuts &bolts, absolutely horrible sound.
it may also only screech at higher rpm 2k+ (high pitch) but not at idle.
steering pumps -whine or moan, usually when cold or at full lock, sometimes from low fluid, or the fluid needs to be changed
alternators get a consistent metallic noise/groan (rotational)=bad bearings
you can grab a $10 mechanics stethoscope and pin the source down that way

 

[Foggy]

Left side would be alternator. IF not in the belt system itself, my guess
would be alternator bearing is going bad. Easy to diagnose. Easy to Replace
if needed

 

[EddieC]

Doubeleive, I tried a long screwdriver on the alternator and PS pump and only heard bearing whirr but it was not a screech time. Maybe a stethoscope would be worth a try.
The only known things at the moment is it's on the left and the weather is not cooperating being 20 degrees and lower every day. Nothing get's done then.

 

[EddieC]

Thanks for all the input. Things to try when it gets tolerable outside.

 

[Doubeleive]

Doubeleive, I tried a long screwdriver on the alternator and PS pump and only heard bearing whirr but it was not a screech time. Maybe a stethoscope would be worth a try.
The only known things at the moment is it's on the left and the weather is not cooperating being 20 degrees and lower every day. Nothing get's done then.

it can be hard to tell where the noise is coming from sometimes, stethoscope will pin it down.

 

[OR VietVet]

How did you decide it is the left-d/s of vehicle?

 

[EddieC]

How did you decide it is the left-d/s of vehicle?

By Listening.

 

[homesick]

Thanks for all the input. Things to try when it gets tolerable outside.

How is waiting for "tolerable" temps gonna help if it's only noisy at 20* or lower?

joe

 

[EddieC]

How is waiting for "tolerable" temps gonna help if it's only noisy at 20* or lower?

joe

Meaning?
It's too cold to work out there; -3 degrees tonight, high of 11 degrees tomorrow and attention getting wind throughout.

 

[EddieC]

Came across an interesting take on a stethoscope.

 

[rdezs]

If it only occurs below 20° and the vehicles parked outside, and it completely goes away after the engine gets warmed up...my guess is it's simply frost building up on the serpentine belt. Temperature that cold does make the rubber in the belt more brittle and less flexible. If this frequently happens every morning for several minutes, the end result is the belt becomes glazed and can't grip the pulley very well, eventually resulting in being noisy all the time.

My second guess would be below 20° is negatively affecting the spring in the tensioner.... In effect, it simply can't provide enough tension. Also should improve once there's warm air coming off the radiator. (If that's the case.... It would probably result in belt slippage around the smallest pulley.... The alternator) The idler pulleys don't have any drag, so I wouldn't expect it to be from them.

By third guess is the roller bearings in your idler pulley, related to the type of grease that was used for lubrication is not suitable for such cold temperatures. (In which case the sound will get worse over time, even after warming up as it will ruin the bearing)

 

[EddieC]

If it only occurs below 20° and the vehicles parked outside, and it completely goes away after the engine gets warmed up...my guess is it's simply frost building up on the serpentine belt. Temperature that cold does make the rubber in the belt more brittle and less flexible. If this frequently happens every morning for several minutes, the end result is the belt becomes glazed and can't grip the pulley very well, eventually resulting in being noisy all the time.

My second guess would be below 20° is negatively affecting the spring in the tensioner.... In effect, it simply can't provide enough tension. Also should improve once there's warm air coming off the radiator. (If that's the case.... It would probably result in belt slippage around the smallest pulley.... The alternator) The idler pulleys don't have any drag, so I wouldn't expect it to be from them.

By third guess is the roller bearings in your idler pulley, related to the type of grease that was used for lubrication is not suitable for such cold temperatures. (In which case the sound will get worse over time, even after warming up as it will ruin the bearing)

Thanks, more points to check out. I hadn't guessed belt slippage.

If it is near or below 20 degrees it does not go away with any amount of local driving but it is a bit imtermittant, meaning it's here, then not, then back again depending the the rpm. At much above 1500 or it's quieted down.

If the weather warms up a bit but still freezing territory, it may subside. There was no noise at and above a certain temperature, perhaps high 30's. We are in the middle of a heck of a cold snap so when it warms again perhaps any lasting effects will show themselves more consistently. It's odd that it comes and goes.

 

[rdezs]

It may be glazed from so much slippage....will need replaced most likely. I'd wait till this freeze is over though

 

[marktrafton]

If you can do this safely, with the engine running and the noise present, use a can of WD-40 with a spray tube on it and spray the rubber grooved side of each belt with a quick shot of WD-40. If the noise changes or goes away consider replacing that belt or belts. If it does not, remove one belt at a time and see if the noise goes away. If the noise is still present after all belts have been removed, you have eliminated belts, tensioners, and accessory drive bearings.

 

[EddieC]

If you can do this safely, with the engine running and the noise present, use a can of WD-40 with a spray tube on it and spray the rubber grooved side of each belt with a quick shot of WD-40. If the noise changes or goes away consider replacing that belt or belts. If it does not, remove one belt at a time and see if the noise goes away. If the noise is still present after all belts have been removed, you have eliminated belts, tensioners, and accessory drive bearings.

Thanks. Following through.
Will the WD-40 damage the belts?

UNfortunately (?) today it is in the upper 30's out there and try as I may I can get the screeching noise.
I pulled the upper main belt and none of the pulleys/tensioners make bothersome noises or4 have noticeable play.
There is a noticeable noise inside the PS pump with the cap off and running. Fluid is original and smells burned.
I am curious if the system picks up moisture like the braking system and if so could the extreme cold cause ice in the system?

 

[B-train]

I had that last 2 weeks back with my 2008 in -20F. My assumption was it was an idler pulley or the PS pump hating life. It would go away after some driving most days. It was 10 days of sitting outside, frozen ass cold below zero mornings.......not a fan.

When I got back home from my trip and could park it back in a heated shop (where it belongs, poor fella) I was able to look things over. I found both pulleys for the belt tensioners sounded a little dry when spun by hand. I popped them off, pulled the dust seals, washed/blew them clean, and repacked them with new high temp grease.

Quiet as a church mouse now......drove it Sunday to ORD at single digit temps and it never made a peep. I did change the PS fluid lasr summer, its super easy to do with an extra set of hands and 3 quarts of new fluid.

 

[Ghoff]

I recently have has a screech that seems on the left front side of our (5.3) engine (2008 Tahoe) when the weather temperature is 20 degrees and lower.
After a certain rpm, perhaps 2000 to 2500, it goes away but effeminately varies with the rpms and comes back when the revs drop but is mostly gone at idle.
It seems like it might be the PS pump or alternator but on a few tries it's tough to pin down.
There does not seem to be an uncharacteristic odor and the alternator seems to be functioning normally based on the instrument panel gage and the state of the battery. The power steering is functional and there is fluid in the reservoir.
Both drive belt tensioners were replaced with oem last year as were the belts.
Also there are no coolant leaks at the water pump and the temperature gage is running normal.

Any thoughts on which might be more likely to make the screeching noise if failing?

I saw an online clip that showed the alternator on some GM vehicles have a decoupler pulley which can screech if it is going bad. May want to google that and see if the symptoms are familiar.