Engine noise?

Just purchased used from Carmax. We do not have a garage so the car is exposed to outdoor elements. We have had alot of rain. Since then when I start the car the engine sounds as if I have a bird chirping away in it. Do you have any suggestions of what this could be? Also, just read on-line of transmission problems in the 2002 Explorer. I am officially afraid I have made a poor used car purchase and instead of taking it back for service I should just give it back to them. Any comments? However, researching used vehichles on-line can't seem to find one that hasn't had transmission problems! !? Help - mother needing reliable vehicle on a budget !

Try this step.
Spray a little D40 to the tension arm, the one that adjusts the belt. If the problem went away, you need to replace that tension arm. If it still has the same problem, you have something wrong with the engine. I don't think the transmission has the problem.
I remember my car had a loud chirp when it was 45k. I noticed the chirp was from the tension.
Tony

Last week, my 5.0 Explorer began making a screeching noise. I noticed that it only occurred between 2800-3200rpms. It doesn't matter if I'm on the road or sitting still, in drive, in park, in neutral, etc. If I stay above or below that RPM range, no screeching sound can be heard. The sound can clearly be heard in the video at the bottom of this post.

*NOTE* - The sound is still present with the serpentine belt removed, so it is not accessory related.

http://s121.photobucket.com/albums/o210/jlatha86/?action=view¤t=MOV00734.flv

After taking a closer look under the engine bay while the engine was running, I decided the noise was coming from the front side of the engine and it sounded like it was under the intake or possibly behind the timing cover. I don't have an automotive stethoscope, but from my younger days, I can remember my grandfather troubleshooting with a stick. I found a suitable "tool" and began listening and feeling different areas of the engine. When I touched the top of the camshaft sensor, I could immediately feel the vibration much stronger than anywhere else. When the screech occurred, I would compare the feeling to that of hitting a solid object with an aluminum baseball bat. It made sharp vibration. With that being said, I believe the culprit is the camshaft synchronizer (aka crankshaft angle sensor depending on where you buy the part). After doing a lot of online research, I've determined that Dorman products should be avoided at all costs due to inferior build quality. A1 Cardone seems to make acceptable remanufactured units, but I decided to go with a genuine Motorcraft part. It will probably take a couple of hours to swap because the spark plugs need to be pulled to ensure the #1 piston is at TDC on the compression stroke. If any of you have changed plugs on a 5.0 Explorer, you already know how time consuming that job can be by itself. If anyone finds this thread in the future and you're not mechanically inclined, this is definitely a job for a mechanic. Proper installation of this part is vital to both the firing order and your oil supply.

I just wanted to followup. I replaced my camshaft synchronizer last Wednesday, December 9th, and everything has been functioning flawlessly. Here's a short video of the sound the synchronizer was making once it was out of the vehicle. As you can hear, it is quite harsh. I've found a few videos on YouTube of other bad synchronizers, but they sounded much more birdlike.

Loud metal on metal noise for a few seconds after starting.

No, the noise is definetly comming from the engine. Sounds like the lifters or push rods running with no oil. But the noise goes away after a few seconds as if oil has reached the source of the noise.

Hi
I use 5w30 and a Fram oil filter. As far as temp, its funny you ask because it only happens when its cold outside (40 or so and under). I live in Co.
Thanks

OK, thank you very much Joe. You have been very helpfull!

Rod