Thread: Need help, Engine Knock

Hi everyone,
I have a problem with a 2002 grandprix 3.8l SC
It has a metallic knocking sound coming from the passenger side of the engine. Sort of like a ball bearing in a can. I reviewed previous posts for the last hour to see if anyone else had a solution and looks like it can be several things, so heres where I am.
Engine knock is louder when the air conditioner is turned on.When turned off it quiets down considerably. I removed the super charger belt and still have the noise. I used a long screwdriver as a stethoscope and tried to isloate and found the accessory belt tensioner has a pretty good vibration to it. Supposedly the pulley on the belt tensioner was previously replaced along with the power steering pump in the past. I removed the accessory belt and started the car for 10 seconds and the noise went away. I spun and checked for play/looseness all the pulleys on the engine, 8 total and no trouble found. The water pump doesn't leak from the weep hole and wasn't for sure if the accessory belt tensioner assy can go bad hence the vibration when the engine is running or if some other component i.e.(water pump, bad pwr streering pump) is transferring it to the belt tensioner. I can't afford to shotgun the problem, have limited funds.
Thanks for reading, sorry so long, just wanted to be concise.

Sounds to me like a bad bearing in the compressor clutch hub, are you sure it spins smooth? Does it spin totally free with no rough spots?

I have some other theories, based on the idea the vibration your seeing in the belt tensioner is normal. That “ball bearing in a can” sound from that part of the car typically means one thing. You have something stuck in and bouncing around your vent fan blower. Just turn off your vent fan and recheck for the noise. Another theory is, it might be one of your radiator fans. Be aware the one behind your A/C condenser will always start when you turn on the A/C. Another easy thing to check.

I’ll be around most of the day if I can help more. Good Luck

No, I just went out and checked the A/C comp. a 2nd time and it turns smoothly and works fine too. Noise is still there with the fan off. My guess is when the A/C kicks on it puts a load on the belt tensioner assy and highlights the problem. Definitely coming from the engine belt area. I thought the the tensioner bracket were it pivots was just a big spring with no bearings to go bad, Just the bearing in the pulley. Was hoping someone had this same problem so I would know for sure.

Well, I’m at a loss now. Hopefully someone here can help you. My only advice now is make sure your AAA is paid up and don’t plan on using this car for long trips. What ever it is, it will probably fail in the next month.

Yeah, I think I will try that, wish I had 3/4" impact.

After some more research I found this video complements of stlmo_gtp he had the same problem last month. Thanks for your help

I just got done changing the harmonic balancer and it fixed the problem.
Only issued I had was that I couldn't use a harmonic balancer puller because the 3 bolts you use to thread into the balancer to pull it off wouldn't thread into the balancer to pull it off. So I used a 2 jaw puller instead, worked great.

If you guys ever have any knocking, clacking sound coming from the belt side of your engine don't forget about the harmonic balancer in addition to the pulleys.

Thanks for everybodys help!