Need help identifying noise, Mazda 2.0L

I

i6pwr

Joined
May 4, 2008
Messages
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This is a 2006 Mazda 3 with the 2.0L and 5 speed. 140K miles and it sounds like a telltale power steering pump whine from a distance but I think this has electric power steering. No change in pitch if the alternator is loaded up, but it does change when the air conditioner is cycled. I don't know if that's from the load or brief change in RPM. Haven't put a stethoscope on it yet and sorry for the short video, but the whirring noise should be evident.

Curious if anyone has experienced this.


 
I'll try to get a better video, but in the beginning, the whirring sounds like a hollow, plastic sound. No change if I opened the oil cap though.
 
Rand said:
Sounds like Fan and engine noise
Click to expand...

Fan was actually not running, the whirring noise at the beginning of the video is audible from standing over 20' away. Mimics a PS pump that's low on fluid. I will try for a better video when I get a chance.
 
Check your Serpentine belt idler,and replace/check belt while you are there. may also other belts to check.
 
AC compressor is almost under the crank pulley, was able to get a stethoscope on the hard line leaving the compressor, noise was isolated to that area, alternator, idler, water pump were quiet.

Here's a better video.

 
Could be the AC compressor, the good news, or bad, depending on your opinion, is that the compressor is on a separate stretch belt. It can be removed, or cut off, and it won't affect the rest of the accessories.

Actually, before you do that, relieve the pressure from the belt tensioner while the engine is running to see if it has any effect on the noise. It's right on top of the engine and super easy to access. If there is no change in noise, it's the AC compressor, since it runs on a separate belt.

Screenshot 2026-05-29 094403.webp
 
Sounds like one of the pulley's bearing. The tone change is due to rpm change on the AC clutch engaging disengaging.

I had a lot of noise once before my water pump wear out and got worse, took my mechanic a long time to figure out finally it was the water pump. With today's one belt only system it is impossible to take off one belt at a time to figure out.
 
KrisZ said:
relieve the pressure from the belt tensioner while the engine is running to see if it has any effect on the noise
Click to expand...

I could try that, I should have mentioned earlier it's not my car but I'm thinking of possibly buying it, this noise definitely gave me some pause and concern.


PandaBear said:
Sounds like one of the pulley's bearing
Click to expand...
It does, I agree but the growl is a new one
...usually they have a higher pitched noise, this almost completely mimics a PS pump but not the case here.

Stethoscope puts the noise at the compressor but I could only reach the hard line manifold at the rear of the compressor.

My main concern is the compressor is bolted to the bottom of the block so I wanted to be sure it's not picking up an internal engine noise but I can't think of anything that would sound like that other than a bearing.
 
i6pwr said:
I could try that, I should have mentioned earlier it's not my car but I'm thinking of possibly buying it, this noise definitely gave me some pause and concern.



It does, I agree but the growl is a new one
...usually they have a higher pitched noise, this almost completely mimics a PS pump but not the case here.

Stethoscope puts the noise at the compressor but I could only reach the hard line manifold at the rear of the compressor.

My main concern is the compressor is bolted to the bottom of the block so I wanted to be sure it's not picking up an internal engine noise but I can't think of anything that would sound like that other than a bearing.
Click to expand...
You could just remove that belt, and that would tell you right there if the noise was internal to the engine. I'm still betting on the A/C compressor. Even then, it's not that bad of a fix, if the rest of the car is roadworthy.
 
i6pwr said:
I could try that, I should have mentioned earlier it's not my car but I'm thinking of possibly buying it, this noise definitely gave me some pause and concern.



It does, I agree but the growl is a new one
...usually they have a higher pitched noise, this almost completely mimics a PS pump but not the case here.

Stethoscope puts the noise at the compressor but I could only reach the hard line manifold at the rear of the compressor.

My main concern is the compressor is bolted to the bottom of the block so I wanted to be sure it's not picking up an internal engine noise but I can't think of anything that would sound like that other than a bearing.
Click to expand...
AC compressor is a pump just like PS but I guess different. I had a water pump that at the end of life gradually sound like that. I originally though it was just my stuck piston ring but it turns out to be the water pump, took my mechanic a few hours to figure out. Bad bearing don't always squeal.

Probably hope for the best (a new pulley) and plan for the worst (an AC pump)
 
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