Reader Question: Underhood Screech?

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Here’s the latest reader question, along with my reply!

Susan asks: I have an ’08 Saturn Aura with a problem I wanted to get your opinion about. There is a loud screeching noise coming from under the hood that gets worse as I accelerate. Other than the noise, the car seems to run fine but the noise worries me and I would like to figure out whether I should be worried.

My reply: There may be reason to be worried – but hopefully not. Odds are the screech is emanating for one of two and possibly both reasons. The belt that drives the engine-driven accessories may be slipping/failing and/or the tensioner pulley that maintains the correct . . . tension on the belt may be failing. There is a simple, no-tools-required way to diagnose this.

Get a can of WD-40 and – with the engine off – spray the WD-40 all over the belt and the pulleys (your Aura has a transverse or sideways mounted engine and so the belt/pulleys will probably be facing the passenger side fender rather than straight ahead, at the front of the car (which it would if the car were rear-wheel-drive rather than FWD).

No start the engine. If the screech goes away, you have identified the problem as the belt or the pulley or both of them.

Replacing the belt is easy on cars with a single (serpentine) belt that drives all the accessories and which is “snapped” into place via the tensioner. The basic process is:

Release the tension on the belt using a wrench or socket on the tensioner pulley; slip the belt off the pulleys, talking care (take a photo) to note the proper routing of the belt so that the new belt is installed correctly. With the belt off, check the tensioner pulley for free play and any weird noises by spinning the pulley. If it doesn’t wobble or sound scratchy and turns freely it is probably ok.

Now route the new belt over the pulleys and snap it into place using the tensioner pulley. Double check the routing and then start the car and see whether the noise has gone away. If it is still there, the problem is probably the tensioner pulley.

A belt should cost about $15-$30r so, depending on which brand you buy and where you buy it. A replacement tensioner should cost about $40-$50.

If you can change your own oil, you can do this job. If you can’t and need to pay for the labor, the total cost shouldn’t be more than $150 in parts and labor.

. . .

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