My vehicle: 1998 Dodge ram 1500 5.9 van
I started to get this screeching noise (like metal rubbing together) from under the hood a few weeks ago. After troubleshooting together with my neigbour I replaced the tensioner (it was doing quite a bit of jumping and sounded very much like it would be the culprit), which helped eliminate some of the jumping but not the noise. Next the idler pulley-no change.
The noise begins with start up, persists in neutral, park, any gear, while sitting or driving, no difference. It also does not matter if the heat/a/c/fan inside is on or off. Any setting will not matter or change the noise. One difference happens when the clutch engages-the screeching sound is reduced to a wirring (like a chirping bird), then goes back to more of a screeching when it disengages. Another difference makes the outside temperature. I had noticed that when I go to work (day time) the noise would stop or reduce to a very slight chirping once in a while, after 2-3 miles. On my way home at night (cooler temparature) it takes longer, 5-6 miles. Day time temps have been around 80 as of late, and the noise stops much faster now and is not near as bad at start up as it has been with colder outside temps when I first started having the noise. All gauges function normally, no fluctuations. The belt is in good shape. Any help in further troubleshooting this issue will be most appreciated.

 

If you're referring to the A/C compressor clutch, then the problem is the A/C clutch bearing. If you want to confirm this, remove the belt and start the engine briefly. I'm sure the noise will be gone.

 

Yes I was and thank you-I will try what you suggested!

 

When was the belt last changed? Todays belts will actually look good when it is worn completely out. Modern belts don't crack when they wear as the older belts did/do. These newer belts can actually wear the pulleys out if not changed regularly.

 

The AC compressor runs on refrigerant and compressor oil. If you had the system charged a few times without adding in compressor oil, then yes, the compressor pistons or continuous swirling clutch is scraping metal to metal.

Just recently, I had replaced the belt on the van. It had screeched worse than the lady at an opera. I tried belt dressing. It was good for the first mile. Next, i tried lithium grease on the outside part of the belt. It took three applications over a week. No more screeching.

Oh, what started all of this prior was a bad radiator and a water-pump that went bad. the water pump would screech while turning too. The impeller inside would scrap the inner beveled surface.

 

It occured to me that if I start the engine without the belt on the only thing to be confirmed would be that any one of the pulleys might be making the noise. Please keep in mind I'm not a mechanic, just going by logic here and trying to learn.

 

Thanks for your input. I have never changed the belt since I bought the van 7 or 8 years ago. I don't know if it had been changed before that. So would this be an older belt or one of the newer ones? How often should the belt be changed? I don't drive the van much, just back and forth to work and shopping trips. Occasionally I pull a trailer.

 

The system has not been charged since I've had the van. Could it still have gotten low on oil? I guess this might be a possibility once I start the engine without the belt and the noise is still there.

I kind of ruled out the belt screeching as the noise I'm hearing has a certain rhythm to it. This might be a stupid question, but someone once told me that the only stupid question is the one you don't ask, so here it goes: What does the lithium grease do for the belt?

 

Thanks to all who have given some input as well as insight so far. Guess I have my work cut out for me. One thing i forgot to mention in my original post is that the noise gets worse with acceleration. When I take my foot off the gas it subsides. If I accelerate slowly, I hear a slight increase, if I push on the gas suddenly, as in trying to increase speed fast, it's very loud. Hope to be back with some results tomorroiw.

 

I had the same type noise that went away when my water pump quit and broke the belt. After I replaced the water pump and the tensioner pulley, I still had the noise. Turns out that it was an alternator bearing.