I have an engine noise on my 2000 Dodge Caravan with the 3.3 engine. It sounds a lot like the grinding of a rotating part. It occurs at start up, momentarily, then goes away. If I drop it in gear and start doing low speed maneuvering in the driveway, it comes back. If I turn on the AC it comes back. In all cases, the noise goes away at around 1200 rpm.
The noise occurs again, when I shut the engine down.

The engine performs and runs smooth and normal otherwise. No stalling, stumbling, or bad gas mileage to report.

I can "feel" the noise with my hand, when I put my hand on the ac compressor bracket, or the intake manifold, or the valve cover. I've tried the listening through the stick method, and it seems to be coming from the front area of the engine. But I can't be sure. It is something internal. Let me describe:

I thought it was my AC compressor or clutch going bad. The fact that my AC had stopped working well, and was making jet engine noises at high rpm helped me decide this. I replaced the compressor. The AC works great now, and the jet engine noises went away. But the grinding noise is still there. As described.

I wishfully thought it was the belt tensioner or idler pulley. I replaced both of those. Noise still was there.

I pulled off the serpentine belt, and started the engine. It made the noise, very briefly as it started, then went away completely. It made the noise again briefly as I shut the motor off. So it's still there without any of the accessories turning.

I'm kind of stumped. the noise is loud and obnoxious at idle when under load. It just can't be good. I've read theories about similar sounding problems, saying they could be loose timing chain, bad oil pump, slapping pistons, crank journals, flexplate/flywheels cracked.

I'm going to try doing an oil system flush, and then I'll change it out with a little thicker oil. See if that makes any difference in the noise. Currently I'm running 5w-30 Mobile 1. I think. I'll let you know if it changes anything. I'm also thinking I want to make a short video of the car idling and making the noise for my video camera. I'll post that on youtube and link it here.

Meanwhile, anyone have any good theories? Or similar problems they've solved? I just don't want to start tearing into the engine willy nilly until I have a better theory.

I had the EXACT SAME situation with a Chrysler T&C @ 165,000k miles. Same 3.3 engine as the Caravan. It turned out the problem was with the starter solenoid. The solenoid was NOT pulling the starter gear far enough away from the flywheel. At idle the crank 'walks' towards the starter (within the crank journals) the amount of 'crank walk' is so small, but the starter gear is super close to the flywheel. Under heavy load, the crank walks AWAY from the starter giving just enough clearance for no contact being made between the 2 gears.

What I did was inspected the starter and the flywheel gear. I saw damage to the outside edge of the flywheel gear teeth. and the starter gear. I ended up having to replace the starter and solenoid, but it fixxed the problem. The minivan currently has 180,000k miles on it and has NOT made the same noise since the replacement.

Still using the same flywheel.

The noise my van was making was similar to (trying to describe) it would sound something like constant random rattling with some clanging type of noise with a little bit of ringing once I shut the engine off.

The starter sounds like it's well worth checking. If that looks ok, I would suspect a cracked flex plate as you have already read about. It's an all too common problem. Maybe you are hearing the first indications of it. The flex plate is bolted to the torque converter inside the transmission bell housing. You can see it with the starter removed or at the inspection plate at the bottom of the bell housing.

I feel the utter fool. Remember how I swore up and down that it was still making the noise slightly when the serpentine was removed?? Well, I don't know what I heard at startup without the belt, but it wasn't the main noise. Maybe a heat shield, who knows? I'll try and figure it out.......after I replace the belt tensioner!

I was running it today, having the wife turn the AC on and off, to put load on the engine, which makes the noise get worse, then better, respectively. When I stared at the tensioner, it was bouncing in time with the rattling noise. Almost so fast I couldn't see it.

I've got one coming, and I'll throw it on. We'll see if all the noise goes away.

I feel foolish, but relieved if it does. If not, I'll keep looking at stuff, starting with what has been suggested.

Thanks for the responses.

Could be the tensioner or the idler pulley. I don't know when they started to used it, but the alternator on my 2001 G.C. has a decoupler pulley. They tend to go bad and make a noise.

I believe 2000's did not have them yet, but I'm not sure if yours has it or not.

Good luck.

I picked up a tensioner arm Assy at napa, and installed it. Which I might add was a pain. And the noise is still happening but not nearly as bad. The noise is still being made by the tensioner arm. The new one doesn't bounce up and down as much, but it still does. I actually put a wrench on the tensioner pulley mount bolt while the engine was running, dangerous yes, and I put pressure on it both ways while the ac was on and the noise was happenning. When I held it, cushioning it with my hand so to speak, the noise completely went away. It was still bouncing a little, but my pressure on it was dampening it. So I guess my question now would be: what would make the tensioner bounce around like that? The new one as well as the old one. ???

I was thinking maybe a component is putting rapidly changing load on the serpentine? Not sure if that's plausible or not.

Oh, my alternator doesn't seem to have any special clutch thing on it, it seems to be a straight pulley. I got pretty intimate with it while replacing the tensioner.

I remember having tensioner wobble a bit in my 1996. I hope yours isn't this bad, but you'll get the idea of what happens, check out this YouTube video:

http://www.youtube.com/watch?v=4EXYP1CmL9Q&feature=related

I guess that's why they're using decouplers now.

As far as the noise, if you already changed the tensioner and the idler, you may have bearings on the alternator or A/C compressor going bad. Or it could be the water pump or the power steering pump. Get a section of hose and hold one end up to your ear and the other end near the other accessories. It should help you isolate the source of the noise.

Be very careful, obviously.

Hopefully it's not your PS pump. If you think changing the tensioner was a PITA, you got a heck of a surprise coming. There are some posts on how to do it, I even posted one. If you have to change the PS pump, I recommend you do a search so you know going in the best way to go about it.

Good luck.

Thank you for linking t that video. I actually enjoyed seeing that. That is the exact stuff my tensioner is doing. I'll try out the hose listening method. The source of the noise I can hear is the bouncing tensioner, but something else is obviously making it do that. Hopefully I'll be able to hear something else, if something is going bad it should make some kind of identifiable noise, I hope.

I'm getting annoyed at chasing the ultimate cause if this noise. You're so right, I do hope it isn't the power steering pump!!

I keep telling myself: at least it doesn't seem to be the flexplate, or rod knock, etc.

Thank you for linking t that video. I actually enjoyed seeing that. That is the exact stuff my tensioner is doing. I'll try out the hose listening method. The source of the noise I can hear is the bouncing tensioner, but something else is obviously making it do that. Hopefully I'll be able to hear something else, if something is going bad it should make some kind of identifiable noise, I hope.

I'm getting annoyed at chasing the ultimate cause if this noise. You're so right, I do hope it isn't the power steering pump!!

I keep telling myself: at least it doesn't seem to be the flexplate, or rod knock, etc.


Have you taken the serpentine belt off and ran the engine a little to see if the noise still exists??

Yes, I did run it without the serpentine. I thought I might have heard the noise when I initially cranked it over, but no noise was heard during operation, or at shutdown.

The noise, is physically being made by the belt tensioner. I can see it bouncing in time with the noise, and if I put a wrench on it, and cushion it from bouncing as much as it does on it's own, the noise completely goes away.

As to what it causing the tensioner to do that, is what I'm figuring on currently.

Idler pulley, tensioner pully, tensioner arm, AC compressor, and belt. Have all been replaced with new in the last month. The noise is still pretty much the same as when I started.

Feels as if I'm just loading the parts cannon, and firing at random.

alternator very common

Did you ever come up with anything? My 3.8 is doing the same thing. VERY frustrating.....