Engine noise

Lately my 95 Explorer has been making an odd noise in the engine compartment. It doesn't do it until you drive it (doesn't matter how much, how hot/cold, or anything). After its been driven and I let it idle it makes a sound very similar to driving with the parking brake still on. It will continue to do this until I put the clutch in and rev it to at least 3,800 rpm, then the noise stops, as soon as it goes below 3,800 rpm the noise starts again. I have checked all the belts. It has a history of having problems so Im not supprised this is happening. Its been to the dealer at least 25 times and I've fixed it at least 15 times. Any ideas on what could be making that noise?

What specifically does the noise sound like? Screeching, squealing, rattling, dragging chain, whistling, thumping, thud, popping, windy, etc. Could be a lot of things. If it's a squeal or screech it probably needs a new fan belt. If it's chain dragging sound it's the timing chain.

A combination of squealing, screeching, and chain dragging.

You mean like the beginning of the song Money, by Pink Floyd? Kaching-chang-scratch-da...da..da.da.da....da.da. Your stereo is probably too loud. Fix: turn it down!

Haha. No its not that. It does it with the stereo off too.

Have you tried listening in the engine compartment when you notice the noise, after you've driven it, with the hood up? You might at least be able to get an idea of the general location of the noise. Which would help in identifying it.

Its comming from 2 places. The screeching and squealing is comming from the right side of the engine and the chain dragging is comming from under the distributor.

Without actually looking at it myself, I would say 1) Alternator, and B) Timing chain. Some good places to start!