2004 Chevrolet Trailblazer, Bearing Noise Under The Hood

This 2004 Chevrolet Trailblazer came in with a fairly loud roaring/whining noise coming from under the hood while the engine was running. I was pretty sure the idler pulley bearing was making the noise so I loosened the tensioner assembly and took the belt off. It took a 3/8 square drive adapter to connect to the tesioner assembly. A 3/8 ratchet would also work.

I reached down and spun the pulley by hand and it felt a little rough. The alternator and a/c pulleys seemed smooth, when turned.

I used a 3/8 drive ratchet and 15 mm socket to remove the attaching bolt for the idler pulley.

The pulley had a fair amount of rubber built up on the outside of it that it was collecting from the backside of the belt.

The pulley, bolt and dust shield.

With the bolt and dust shield removed it is pretty evident that the bearing is faulty visually.  The upper edge of the bearing is covered in cooked bearing grease. The grease boiled out of the bearing as it failed.

Be careful removing the pulley as there is a good chance you will cut yourself in the fan shroud’s sharp edges. Maybe some day the manufacturers will care enough to make working on a vehicle safe. I can dream can’t I?

The old and new pulleys side by side.  Note that the bearing sizes are the same for both pulleys. There are some replacement pulleys that have a smaller bearing.

I cannot see using a pulley with a smaller bearing in a situation where a bearing has already failed. You can see from the box that I used a quality name brand part.

All back together and quiet as when new.

I wish the customer would have sprung for  a new belt, but that was their decision.

I have replaced a few of these now and I guess the reason I am seeing them is because my customer’s think that the alternator or air conditioning compressor is making the noise. I won’t complain though it is a pretty easy repair.

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