Serpentine Belt / Groaning on Startup

[BostonETC97]

The last couple of months I've had a hiccup after each startup. Once the engine starts, there's a loud growly grinding noise for about 3 seconds from under the hood. Every time I go to diagnose it, it won't duplicate. When the 'grinding' occurs, the car temporarily bogs down, RPMS drop, noise stops, and never comes back until the next startup. Odd!

It happens with or without the A/C activated, so I doubt it's the compressor. The alternator is relatively new, and the PS pump seems to be operating normally. If the tensioner or idler pulley was starting to fail, does it make odd noises?

The belt is less than two years old, so it shouldn't be out of spec yet. Just went on to 93k miles, otherwise still trouble free!

Thanks for all the help!

-Scott

[BodybyFisher]

First thing I would check if your AC HUB. The problem with that thought is that the hub would overheat very quickly and ruin the bearing and short the clutch windings. Its not likely that it would last two months with a bad hub bearing.

Look at your belt to see if it appears that it is slipping, it will look shinny. Its possible that your tensioner is not putting enough tension on the belt and your alternator is slipping. Just a thought. However, you would get a code regarding charging, so its unlikely. Have you checked for codes?

Drain your oil and see if you see any shiny metal filings in it. I'm not sure but maybe its possible that a timing chain is messed up, again just a thought. If you can filter the oil through a nylon stocking that would help gather the filings and make them easy to see..

You should also take the serp belt off and carefully feel each accessory and wheel to see if you feel any roughness. Pay close attention to your idler wheel. Look for wobble also.

Your problem is pretty unique, and I am just guessing here, but as you already know your problem is not an easy one.