There is a squealing sound coming from the engine on start up and when sitting idling. Is it the serpentine belt or are there other reasons for this. Is that the only belt on a 2006 toyota corolla automatic.

serpentine belts do not stretch as you describe because the tensioner keeps them tight so they just break. It is probably hard and cracking and need s a new one so try that first . The ac has nothing to do with the belt as it will be a low gas problem from leaks and the heat is a coolant problem or a control problem from inside the car.. The grinding sound may be a pulley bearing or some other bearing failing. Why don't you take it to a repair shop to find all the faults so that you can work out how much it is going to cost.

it is the belt it is either to tight or not tight enough

Replace the crank pulley before it costs you an arm and a leg. It has caused this problem. don-ohio

Tensioners should be replaced about every 80 thousand km when u let of the gas it relieves tension on belt tensioner if the spring inside is wearing out chances are there's ur squealing sound would sound like a belt squeal not a bearing

There are several heat shields that can squeak or you could just need a new serpentine belt. Unfortunately, a lot of things can cause a 'squeak' but without knowing what area it comes from, if it changes with engine speed, or vehicle speed, I can't give you any pinpoint information.

Based on what you described, sounds like the bearings on one of those items are worn out. Is it a squealing sound??

Another thing, is maybe your serpentine belt is just loose or old. You could go get a can of belt dressing and spray on the ribbed side of the belt, as it is idling.

Are you sure you don't hear anything like a chirping sound when the engine is idling? Have you popped the hood and listened while the engine was idling? Have a friend sit in the driver's seat while you pop the hood, tell them to press the accelerator and then listen for the squeal. I would bet dollars to donuts the problem is the serpentine belt is worn and needs to be replaced.

Sounds to me like a dry, loose or worn serpentine belt. With the motor idling, lightly spray the serpentine belt as it's spinning with WD-40 or other oil based lubricant (Don't spray near the alternator). If this doesn't work, turn the mortor off and check the tension and for cracks or worn spots. The brakes will not squeal when you are completely still.

the squealing when you start it and are idleing s probably the fan belt or serpentine belt, it may need to be replaced or it could be that it needs some belt dressing sprayed on it. belts will squeal if they are damp from the moisture in the air. as for the fan you most likely have an electric fan in your car and they sometimes run for a few seconds after you shut the vehicle off. It would be a good ideato have someone ceck the fan for you and the belts to be on the safe side.