harmonic balancer - (now me too) symptoms and repair
Symptom: Loud rattling noise at idle - didn't happen slowly over time; rather, it happened suddenly (on mine anyway).
The other day I went to start the '92 SSE supercharged and I heard a rattling noise for a second when the starter motor disengaged. I drove the car home and noticed that there was a now loud rattling noise at idle, but it went away when throttle was applied. My first thought was maybe a broken tooth on the crank or the starter motor, but this wouldn't explain the rattling noise at idle, just the noise while starting.
I listened using a piece of rubber hose, and the noise sounded like it was coming from the harmonic balancer pulley area, or maybe the timing chain/gears behind it, so I removed the 2 accessory belts, one-at-a-time, and ran the engine for just a few seconds, and when both belts were off the noise was gone, so I knew it wasn't the water pump, AC pump, PS pump, or any of the other pulleys.
I used a small mirror to look at the side of the balancer pulley, and I could see that the rubber was cracked and separated on the outside edge where it meets the pulley itself. I also noticed that there were now small pieces of crumbled rubber on the ground under the engine, so this confirmed my suspicion that the rubber on the balancer was shot.
I called a few local dealers. As I called more than one dealer, I learned that one of them gave me the wrong balancer part #, but the other 2 gave me a different (correct) part number and one of them had it in stock. I was surprised to learn that the balancer for the '92 supercharged engine is a different part number than for the '93 and '94. I thought the '92/'93 engines were the same and the '94/''95 engines were the same?
Anyway, I bought the part from the dealer who had it in stock, and paid a local independent shop to install it. It took them less than 1 hour, and they charged $70 for the labor. The dealer wanted $229 for labor, and another local independent shop wanted $200 for labor, so shop around. I would have replaced it myself, but it happened at a bad time :(, and $70 seems very reasonable to me.
'99 Bonneville SLE, white, 112,000 miles
'02 Park Avenue Ultra, white diamond pearl, 88,000 miles