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[Kelly]

I have a low grade rattle vibration coming from the engine compartment on a 2009 Hyundai sonata 65k for mileage. Obviously driving me nuts. Idler pulley replaced. Not it. Front and right front engine mounts are good. The noise is way more detectable when the vehicle is in drive or reverse just idling or revving. Local shops are stumped. It goes away when in neutral or park. Can,t hear it very well when driving. Could be due to cabin noise. Any suggestion? All is appreciated.

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[Kelly]

Forgot to include it is a US made car: automatic transmission: 2.4 liter 4 cylinder Gls model. Runs and shifts good.

[Daniel]

Sounds like an exhaust heat shield.

[Kelly]

Thanks for the heads up. I will check on it in the next day or two and post up a response. If it is: that would be ok with me.

[Daniel]

If that turns out to be the problem, you may want to find a better class of mechanic.

[Kelly]

Definitely; I am on a wild goose chase; I am going over the heat shield schematics and will get under it as soon as I can; one reason it way not be this is the noise is not tin like it is more of a rubbery vibe; I am for sure going to check and post back as I want badly to find it.

[Daniel]

Hmmmm. Well it’s probably not a heat shield then. Are you positive the mounts are good? Even the trans mount? If even one ,mount is bad the exhaust could be bumping the body.

[Kelly]

I am off Thursday and Friday I wI’ll check the trans mount and rear engine mount while I’m under there. Will post the results of the goose chase then. Thanks for the feedback.

[Daniel]

Double check that all the exhaust hangers are in good condition too.

[Kelly]

Will do

[Kelly]

Well I crawled under the car and checked the heat shields and mounts as best I could. I think all is ok on this end. All exhaust hangers are good too. I think it is coming from the A/C compressor area.

The last couple of times when I started it in the cold I have been getting a high pitch whine/shriek immediately when I turn the key. Lasts for only 1 second. It has gone away since the weather has turned warm.

Could all this be related. Could it be a compressor bearing? The low grade rattle vibe seems to be coming from this area. Not sure 100 percent though. I took some video and will post if it is audible in the video.

[Daniel]

Your compressor might be bad. If it’s starting to lock up, the shriek you hear is probably the belt trying to turn it and the rattle might be the clutch (in the compressor). That’s my theory.
Get a long screwdriver put the metal tip on the compressor (with the engine running) and put your ear on the handle of the screw driver. Touch the screw driver in a few different spots on the engine. If it’s loudest at the compressor than you found the offending component. Check the alternator and water pump too.

[Andrew Phillips]

Take the drive belt off and start the engine and see if the noise goes away. If you have more than one belt (my Hyundai has more than one), do them one at a time. If all the belts are off and the noise is still there, it isn’t a belt-driven accessory noise. If the noise does go away, test the pulleys on everything that the removed belt drives. Yes, it is okay to run your engine briefly without the belts. This test is important to conclude whether it is or isn’t a belt-driven noise, and will point out which accessories may be to blame if it is.

[Daniel]

Check the tensioner/idler pulley too. Those commonly go bad. If you don’t hear a noise difference in any of the accessories then I would do what Cap269 said.

[Kelly]

I have a new belt. Need to replace it anyway. I will get do this tomorrow.

[Kelly]

The shop did the idler pulley bearing. It was not the culprit. I don’t trust them anymore . They have misdiagnosed it twice.

[Author]

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