I have an awful rattling noise in my 98 S-10. It does it anytime the motor is running and sounds like a piece of tin that's loose. Could it be something on the exhaust system?

 

Kinda vague...
Please include more details about your S10 including whether it has the 2.2L or the 4.3L engine, and also where the noise seems to be coming from.

 

It is a 2.2. Noise is coming from under truck. Can be heard with truck standing still with engine running. I've heard these trucks have a shield on the exhaust that sometimes works loose. I'm going to try to check that today.

 

From under it toward the back? Toward the front? Right in the center to the left or to the right?

 

I checked it out today; still unsure of where it's coming from. I got under the truck and checked the exhaust. It looked very solid..no loose shields or anything. Then I noticed the noise wasn't down there, it was toward the front of the truck. I raised the hood with it running in park with AC on (that's when it makes the most noise) and still couldn't pinpoint it. At least I'm pretty sure it's not the exhaust now.

 

check you pulleys, otherwise put on some mechanics gloves and start pushing on stuff underneath untill the rattle stops. If it stops then what you are pushing on is the problem

 

My compressor rattles slightly. I'm wondering if you have the same problem. Does it only do it when the compressor engages?
Did you first start to notice it when in a drive-thru or while you were parked idling next to a wall or fence? Thats the only time I hear mine doing it.

 

Another thing is if its like a constant noise or kind of random like it doesn't have a pattern to what it sounds like and does it go away as you change rpm's?

 

I'm sure it rattles loudest when the AC is on and definitely more noticeable when next to a wall, another car or something solid. It also seems to be louder when driven for awhile, or warmed up, I guess. A friend gave me one of those engine stethoscopes, might be a good time to try it out. It's definitely a constant noise. Thanks

 

I'm thinking it could be your tensioner pulley. Its easy enough to replace.