Frog under my hood? Weird noise!

[Cappy]

I've got a 1990 Q45. Bought with 60k miles, now over 250k with no major mechanical trouble! Minor exception; a short took out my alternator. My mechanic replaced the alternator, and when I got it back, the engine seemed much noisier overall -- whirring, etc (It used to be sooo quiet that I would have to shut it off before valet parking so the boneheads wouldn't get in and engage the starter while it idled.) On top of that, there is this "croaking" sound that is loud. At 750 rpm idle, the noise occurs with a period of about just under once per second and lasts about half a second. It sounds like "r.r.r.r.r.r.r.o.k!"When I asked my mechanic - an old-school generalist, but quite knowledgeable - he said, "Oh, that toad, I can't figure it out."I cannot identify an exact source. It seems to emanate evenly from across the entire front side of the engine, just behind the radiator.Could this be one of my chains rubbing ??? Any help is greatly appreciated.

[Trumpkin]

have your guides been done?

[qship96]

The noise sounds like one of the idler pully bearings is failing.....or the new alternator has faulty bearings-

[Infinitiguy19]

I am unsure if this matters in this case but was the alternator OEM?

Was it installed properly?

And did this basically happen overnight?

But I am also chasing down the reason is isn't quiet like a library. I am at the point where I would rather cut offf my ears than listen to another Infiniti mechanic/My dad/any other mechanic tell me my car is "fine" .

But I have read every bit of information I could get my hands on and I still can't find the answer to my problem.

[Q451990]

Welcome to NICO Cappy!

I would invest in a mechanic's stethoscope to help track down your noise. Best $6 you'll ever spend for this type of thing.

http://www.harborfreight.com/c...41966



All of that said, I bet the replacement alternator is your problem... any idea if it was a Nissan OEM replacement, or aftermarket?

Heath