2004 GRAND PRIX GTP WHINING NOISE

  • Tiny
  • kelsiekae04
  • 2004 Pontiac Grand Prix
  • FWD
  • automatic
  • 141,000 miles

I have a 2004 Pontiac Grand prix GTP and it is making a whining noise under the hood. It also gets louder the harder I step on the gas. We have replaced the alternator so that is not the problem. We have started the car without the belts on and it doesn't make the noise anymore but if we just take of the belt that is on the supercharger it makes the noise. Were at a loss and just dont know what else to test.

Thursday, June 9th, 2011 AT 3:23 AM

4 Answers

  • Tiny
  • caradiodoc
  • Expert
  • 25,278 posts

GM has a huge problem with noisy power steering pumps.

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Thursday, June 9th, 2011 AT 3:47 AM
  • Tiny
  • Wrenchtech
  • Expert
  • 19,815 posts

Caradiodoc is prejudice against GM. LOL They actually have far less PS noise problems that other makes like Pord particularly. It sounds like a bearing in the supercharger is bad. That will have a separate belt for the supercharger so you can isolate that for sure

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Thursday, June 9th, 2011 AT 9:53 AM
  • Tiny
  • kelsiekae04
  • Member

Its not the power steering pump as it doesn't make the noise when I turn but it could possible be the pully on the pump. We already took the belt off the supercharger and tested it and the noise is still there so its not that. So the only options we have are alternator(new), Power steering pully since the pump is new, Tensioner (new) Water pump, Crank, and A/c. I really dont want to replace them all to figure our what it is, that will be expensive. Do you know of a way to test this to find which one it is? We have tried spraying WD40 on each of them seperately but it didn't work.

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Thursday, June 9th, 2011 AT 3:09 PM
  • Tiny
  • caradiodoc
  • Expert
  • 25,278 posts

The power steering pumps are the most common cause, not from the pulley, but from the buzzing of the internal check valve. We have already had instances where rebuilt pumps are just as noisy at first but the buzzing dies down over time. You can verify that by listening with a stethoscope at the connection for the high pressure line where it leaves the pump. This is common enough that we don't even bother to diagnose the generators or water pumps. A quick poke with the stethoscope is all it takes.

That buzzing noise is a lot different than the squeak or chirp from the serpentine belt. Don't use any type of lubricants or anti-squeal sprays on those belts as road debris and dust will stick to it and make the squealing worse. To identify a belt squeal, dribble a little water on the smooth side of the belt while the engine is running and the noise is present. If the noise changes, suspect one of the pulleys is misaligned. If nothing was recently replaced, that means the spring-loaded tensioner pulley is the most common cause. The pivot wears and lets the entire arm sit crooked, then the belt has to slide sideways across it as it goes around it. That sets up the squeal.

If the noise was not there until after something was replaced, check that item to be sure it's mounted correctly. The belt should be perfectly inline along all of the pulleys. Look for one where the belt is off-center compared to the rest of them, typically by 1/8" or more.

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Thursday, June 9th, 2011 AT 7:26 PM

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