Help - Strange Noises (Long)

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I need some help diagnosing two completely different noises on my 2003 Dodge Dakota 4.7L. One has been present since I purchased it in October, the other fairly new.

Noise 1 - This noise is best described as a "whirring" noise. It never happens when warmed up, only during "cold" starts (meaning the first start of the day, regardless of whether it is 10° or 90° outside). It is not a constant noise, instead seems to be "rotation" related. This is definitely belt/engine driven noise, because if the engine is revved, the noise changes pitch and goes away at a certain rpm. This noise only happens below ~1,000 rpms, and after driving a mile or two, this noise will completely disappear until the next cold start. The only things I can think of are the P/S or A/C compressor (however, this noise occurs regardless of the A/C being on or off).

Noise 2 - This noise is a rather loud groan/hum that occurs when the A/C is first turned on. It happens when the engine is both cold and warm, but worse when cold. It almost sounds identical to what I call "brake drone", it's kind of a deep whine, but not high-pitched. All I know is this is definitely A/C related.

Maintenance - Last but not least, I need to mention what maintenance has been done already. I have done two turkey baster changes (~4 months apart) on the power steering fluid. I used Valvoline ATF+4 to refill the fluid reservoir. As for the A/C, during the first warm days, I noticed excessive cycling of the compressor. Obviously it was low on freon. I hooked an empty can to my gauge to check the pressure. (My gauge is one of the best you can find that comes with a can of freon, but not a "professional" one by any means. I understand I can't rely on it, but it at least gives a good idea.) It was indeed very low. I added two 12oz. cans of R-134a (WITHOUT any kind of dye or stop-leak additive). The first can helped, but not much, therefore I added a second can. It may not be 100% full, but I didn't want to overfill it either. It at least isn't cycling anymore, and blows fairly cold.

Sorry for the novel, but more info usually helps. Thanks in advance!
 
Try puttting some SILICONE based grease (dielectric grease) on the ribbed side of the belt or the v-side of the belt. Do this at intervals along the belt and when you run the engine, a thin film will spread on the belt. This is a great way to quiet noisy belts and is a nice diagnostic test for belt noise as well. DO NOT use oil based grease to do this as it will cause swelling of the rubber in the belt.
 
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Do not put anything on the belts. I would not use any silicone product in the engine compartment at all. Too much and it can be brought in the air intake and cause issues with O2 sensors. If you suspect a belt causing noise, spray it with a little water. If that quiets it down, I would replace the belt. Any sprays (silicone) might briefly work but it will soon be noisier than before.

The manual for my Chrysler states not to use ATF of any kind but an approved p/s fluid. Check your manual if that applies to you.
 
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Originally Posted By: Lubener
Do not put anything on the belts. I would not use any silicone product in the engine compartment at all. Too much and it can be brought in the air intake and cause issues with O2 sensors. If you suspect a belt causing noise, spray it with a little water. If that quiets it down, I would replace the belt. Any sprays (silicone) might briefly work but it will soon be noisier than before.

The manual for my Chrysler states not to use ATF of any kind but an approved p/s fluid. Check your manual if that applies to you.


+1 Lubener is exactly right on with his advice. The whirring noise could be the idler pulley. I am not sure if a 4.7 has an idler pulley but if it does then remove the belt and spin the idler pulley by hand. If it feels gritty or makes noise or is in any way not smooth and quiet it should be replaced.
 
Originally Posted By: Jimmy9190
Originally Posted By: Lubener
Do not put anything on the belts. I would not use any silicone product in the engine compartment at all. Too much and it can be brought in the air intake and cause issues with O2 sensors. If you suspect a belt causing noise, spray it with a little water. If that quiets it down, I would replace the belt. Any sprays (silicone) might briefly work but it will soon be noisier than before.

The manual for my Chrysler states not to use ATF of any kind but an approved p/s fluid. Check your manual if that applies to you.


+1 Lubener is exactly right on with his advice. The whirring noise could be the idler pulley. I am not sure if a 4.7 has an idler pulley but if it does then remove the belt and spin the idler pulley by hand. If it feels gritty or makes noise or is in any way not smooth and quiet it should be replaced.


this is what I do as well. I've found many problems that way. You can also spin the ac pulley the same way. That could be the culprit as well.
 
My best internet mechanic guesses....

Noise 1 is probably an accessory bearing (alternator, idler, water pump, etc.). Not necessarily a problem- the suggestion to pull the belt and check ALL pulleys for looseness and "gritty" rotation is a good one. If they all check out tight and smooth, its just a roller bearing with cold grease and I wouldn't worry about it unless it starts changing and lasting longer into the warmup process.

Noise 2 sounds like the AC compressor before head pressure builds up. Swash plate compressors like to have a load on them, and until a pressure differential builds the swash plate followers will sometimes rattle a bit on a compressor with some miles on it. It could also just be vapor bubbles going through the expansion tube until the pressure builds up a solid head of liquid refrigerant upstream of the expansion device. Low refrigerant charge will aggravate that sound.

A word of caution: if the AC has lost refrigerant and has been recharged multiple times, it may be low on compressor oil as well and that can contribute to the grumbling noise when the compressor first starts. Or it could have air in the system, which can make the expander valve or tube noisy. You certainly don't want to over-oil a compressor, but maybe an ounce or two of oil is in order for a system that's probably been charged a few times and may very well have a slow leak in the evaporator core.
 
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The first noise you describe sounds like a thermostatic fan, if ii is so equipped. Silicone fluid moves around with a bimetal valve, so that the fan is driven when hot, but not when cold. When they get old, the fluid leaks while shut down, and the fan runs on startup, when the engine is cold.

The second sound might just be a worn AC compressor clutch. It will get noisier, until it quits.
 
Originally Posted By: Jimmy9190
Originally Posted By: Lubener
Do not put anything on the belts. I would not use any silicone product in the engine compartment at all. Too much and it can be brought in the air intake and cause issues with O2 sensors. If you suspect a belt causing noise, spray it with a little water. If that quiets it down, I would replace the belt. Any sprays (silicone) might briefly work but it will soon be noisier than before.

The manual for my Chrysler states not to use ATF of any kind but an approved p/s fluid. Check your manual if that applies to you.


+1 Lubener is exactly right on with his advice. The whirring noise could be the idler pulley. I am not sure if a 4.7 has an idler pulley but if it does then remove the belt and spin the idler pulley by hand. If it feels gritty or makes noise or is in any way not smooth and quiet it should be replaced.


I have found when the bearings start going on idlers, you will start seeing powdered rust collecting on the idler and belt.You might want to check for that on your a/c clutch as well.
 
Thanks for all the input/advice. I forgot to mention the current mileage of 113k. A few things i need to address:

Originally Posted By: Lubener
Do not put anything on the belts...

The manual for my Chrysler states not to use ATF of any kind but an approved p/s fluid. Check your manual if that applies to you.
My truck does specifically call for ATF+4, so no worries there. I also agree with the advice of nothing on the belt. It was replaced by the previous owner (who I believe was thoroughly honest) 10k miles ago. I don't think it's the problem. Funny story though, I used to tell my dad when I was younger "my belt is squeaking, how do I shut it up?" After several minutes of arguing, he grabbed a spare belt, threw it down on a workbench and said "Ok smart*ss, make that belt squeak." After some futile attempts, lesson learned. Something ELSE has to make that belt squeak.
Originally Posted By: Jimmy9190
+1 Lubener is exactly right on with his advice. The whirring noise could be the idler pulley. I am not sure if a 4.7 has an idler pulley but if it does then remove the belt and spin the idler pulley by hand. If it feels gritty or makes noise or is in any way not smooth and quiet it should be replaced
For some strange reason, I have not done this. Yes my dakota has an idler. However, it seems it is sold as one piece together with the belt tensioner (weird?). The previous owner changed the "tensioner" at the same time as the belt 10k miles ago. I can only assume that the idler was replaced as well, but I definitely won't overlook that.
Originally Posted By: 440Magnum
Noise 1 is probably an accessory bearing (alternator, idler, water pump, etc.). Noise 2 sounds like the AC compressor before head pressure builds up... Low refrigerant charge will aggravate that sound. A word of caution: if the AC has lost refrigerant... it may be low on compressor oil as well and that can contribute to the grumbling noise when the compressor first starts. You certainly don't want to over-oil a compressor, but maybe an ounce or two of oil is in order...
Thanks for the detailed reply. I know the alternator is the original, the idler was probably changed, and the water pump was changed at 80k (33k miles ago). So all of the above could be the culprit. As far as the compressor, I am 99% sure it's the original, and I plan on having it checked properly, because there's NO way for me to tell how much oil is currently in it. And I agree, overfilling with oil or freon is bad news.
Originally Posted By: 4wheeldog
The first noise you describe sounds like a thermostatic fan
By thermostatic, I am assuming you are referring to the "electronic" fan. Interesting, I will have to check it. As for the fan clutch (belt-driven), it is new (less than 5k miles ago) and works perfectly.

Again, thanks for all the help. I will update the thread with the fixes when I find them.
 
So I'm tackling one issue at a time. The first repair shop I went to was thoroughly confused when I tried to list all my issues (including minor things irrelevant to this thread). So I started with the "Noise 1" issue. Two shops I went to (that didn't charge an arm and a leg just to LOOK) said all was well except the tensioner pulley. I guess the amount of tension is good, but the bearing is shot.

Coincidentally, later in the evening, I had to accelerate rather quickly. Sure enough, the belt slipped slightly. So now I'm questioning the correct tension advice. I think my current plan of attack is to buy the piece that has both the tensioner arm/pulley and the idler together. This way, I don't have to second guess either part. Perhaps this will cure Noise 2? Guess I'll find out.
 
So to update this thread, I purchased and installed the tensioner pulley, arm, and idler combo piece. Indeed the tensioner pulley was good (previous owner did say he changed it), but the arm and idler were original. The idler bearing was shot. (This is exactly why I don't like other people touching my vehicles, these "professional" shops were going to change the one GOOD thing on there).

BUT, both noises still exist.

To further go into detail regarding noise #2, it is a quick hissing noise followed immediately with a groan. The more I hear it, the more I question if it is actually an interior noise vs engine bay noise. It cycles through these noises 3-6 times with about 5 seconds between each. Also, if I leave the a/c in the on position when I shut the truck off, it will almost never make the noise when restarted.

Perhaps the blend door? Are they vacuum driven somehow (hiss)? Is there a way to check this? What should my next step be?
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Well, I may have found the answer to both problems...

Took it to a different shop to get a fresh set of eyes and ears. With the hood popped, I engaged the A/C. It decided to surprise both of us with something new. Sparks. I guess when the clutch tries to engage on the compressor, something is going very wrong. So I will be replacing the compressor before it decides to
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In addition to the compressor, what needs/should/can be replaced? I am under the impression the orifice tube (filter?) should be replaced, as well as the dryer (same as accumulator?
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) Also, other than the evac. of the freon, how hard is this to do? Thoughts/input?
 
Well, yet another update. I ended up replacing the a/c compressor, accumulator/dryer, and orifice tube filter. Noise #2 is cured
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, however the other does still exist. As I have stated in this thread, the belt tensioner arm and pulley were replaced. The idler pulley is new, fan clutch is new, and now the compressor is new. The water pump was changed at 80k, and I currently have 114k. The P/S does not make any noises when turning the wheel at any temp (have done a few fluid changes). I guess I will try giving them all a spin one more time...

The only possibilities left are crank (i doubt), cam (i doubt), alternator, p/s, and water pump.
 
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