Loud Engine Noises

My car makes a loud noise under the hood that I can’t pin down. The noise is loud, and gets louder when the car is in gear. However, if the A/C is on, then the noise gets quieter, but a different, “chirping” sound is also heard. The car also has been hesitating somewhat when first started. Also, used to have a strong, clean start, without pressing gas pedal. Now it still starts, but seems to struggle sometimes.

Car is 2003 Dodge Caravan SE, 100,000 miles. Spark plugs and wires were just changed, and throttle body cleaned. Fuel system service done 8,000 miles ago. Water pump replaced and belt changed 5,000 miles ago.

Driving is fine. The car has lots of power since I changed the plugs. And it idles fine after I get going. It’s just that noise and the rough start.

Also, had a mechanic look at it, and he took off the belt and checked the pulley and everything connected to the belt. Said everything was fine there.

Here are two videos that were taken moments apart.

The first is with A/C off:

And the second is with A/C on:

Thanks for any feedback!

Your videos don’t work!

Take off SERP belt and listen to motor

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… and while it’s off, rotate and rattle all the driven pulleys.

Temporarily remove the serpentine belt and spin each pulley that the belt rides on, listening for any noise, but mainly feeling for any roughness in the way the pulley spins. Also, if you find any pulley that you can wobble AT ALL, this pulleys bearing is not long for this life and you should change that one out. The only pulley that you will not be able to spin is the crankshaft pulley, which is the lowest pulley.
If all seem tight enough and spin freely, start the engine for a few minutes without the belt and listen for that noise.
You can run like that for about 4-5 minutes (from a cold start) before the engine gets to normal operating temp, but keep an eye on the temp gauge. Don’t over heat it.


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I just edited the post, and now the videos seem to be working now. Let me know if they go out again.

I forgot to note that I had a mechanic look at it, and he took the belt off and checked everything. Said everything was fine. (Edited original post to reflect that.)

Did your mechanic hear the noise? If so you need a new mechanic.

He heard the noise, removed the belt, but didn’t find any problems in the pulley or components. That’s when he suggested changing the spark plugs (which were really needing change). After he changed the spark plugs, the noise was gone, but now it’s back. It seems to happen more when it’s cool out, than when it’s warm out, so that might’ve been the reason there was no noise when he had it. The videos I took were taken at night after temps had dropped.

One can use a stethoscope, or rubber hose, My first guess wold be a belt tensioner.

Is this the 3.9 or the 3.7 ???

I’m wondering if this noise changes as you give the engine a little gas. Does the noise seem to speed up as you give it gas while it is parked???

How long does this noise last. Does the noise go away after the engine warms up.

I agree with @Barkydog and checking with a stethoscope should pin point this.

We had a Ford Van that had a noise that would only occur at a cold start and would only last about 20 seconds. Drove me nuts, because by the time I’d get the stethoscope moved to an area…poof the noise would disappear until the engine cooled off. Sounded like someone shaking a “dice box”.
Turned out that when they changed over to electronic ignition, the distributor was replaced with a shaft and a sensor if I remember right. Turned out that the top of that shaft wore on it’s upper bearing and as it got loose it would wobble and rattle.