[. CrM .]

Hey, I've got a totally stock 94 that has developed a whistling noise coming somewhere from the front of the car.

The noise gets higher pitched as RPM's increase and eventually gets drowned out by engine noise. All I've done so far was change the o2 sensor but I haven't heard the noise until the weather started warming up. The noise stays whether I have A/C or fans on/off. The noise kind of reminds me of a supercharger but much, much quieter.

Anybody know what this noise could be or has/had this happen to them?

 

[Twibs415]

well your problem is something that runs off the engine as you said it changes with rpm. a good place to start is

get your head under the hood while its running see where its coming from

check your accessory belts for tightness and wear. it doesnt sounds like this is your problem because belts usually squeek when cold but old worn or loose belts will always squeal.

if that checks out

remove your accessory belts and give your alternator a spin by hand and see if its loud or grindy feeling. same for the ac pulley and power steering if you have.

see if that helps you find the problem. you can also remove one belt at a time and run the car (not to long) to test where the sound is coming from if its the belts.


good luck

 

[Andy]

Does the noise go away when you press the clutch?


Sent from my iPhone using Magic

 

[Twibs415]

^ +1

 

[3MiataFamily]

Whistle usually means vacuum leak...

 

[ScarfaceThe91]

^ That's what I was thinking too.

 

[. CrM .]

well your problem is something that runs off the engine as you said it changes with rpm. a good place to start is

get your head under the hood while its running see where its coming from

check your accessory belts for tightness and wear. it doesnt sounds like this is your problem because belts usually squeek when cold but old worn or loose belts will always squeal.

if that checks out

remove your accessory belts and give your alternator a spin by hand and see if its loud or grindy feeling. same for the ac pulley and power steering if you have.

see if that helps you find the problem. you can also remove one belt at a time and run the car (not to long) to test where the sound is coming from if its the belts.


good luck

Thanks, I just checked my belts and they seem to be in good condition by look and feel. I'll try taking off the belts this weekend when I have more time to see if it's one of the components spun by the belt.

Does the noise go away when you press the clutch?


Sent from my iPhone using Magic

No, I only hear the noise when I'm in motion but depressing the clutch pedal didn't affect the noise at all.

Whistle usually means vacuum leak...

I kind of thought it was a vacuum leak too but my idle is pretty consistent when warm.
The needle fluctuates a little but only like 1mm which I'm guessing it's normal. I haven't yet been able to thoroughly listen and figure out exactly where the noise might be coming from and it's been difficult because the noise only happens when the engine revs up. I'll check this weekend for the source of the noise.

 

[. CrM .]

Today I noticed that when I started my car it started making yet another noise that sounded like liquid going being sucked through a hose. This was a hot restart though and my car is throwing a PRC Solenoid Valve code but I thought this only deals with air pressure.

 

[2ndGearRubber]

Bad bearings in pullys can cause that sound.

 

[mysteryskittle]

This is hard problem to diag over the net since "whistling" is a subjective term. Do you have any Miata clubs or cars guys around? There's got to be some friendly locals to help you out.

Maybe a trans/diff issue?

Where are you from?

 

[stmserfur]

If its it changes with engine speed then it probably isn't the trans/diff...maybe a leak around your air box? That shouldn't cause rough idle but may be the cause of the noise.

 

[. CrM .]

Bad bearings in pullys can cause that sound.

I'll be taking off and examining all my pulleys this weekend so I'll know if this is the cause by this weekend.

This is hard problem to diag over the net since "whistling" is a subjective term. Do you have any Miata clubs or cars guys around? There's got to be some friendly locals to help you out.

Maybe a trans/diff issue?

Where are you from?

Sorry, I couldn't think of a better term. By tone it could resemble a jet engine and then it rises in pitch as RPM's increase until engine noise drowns it out. I don't personally know anyone experienced in Miata's but I'm located relatively close to Seattle, WA. Also, the noise doesn't dramatically change with the clutch out or the car in neutral which makes me think that this isn't related to the trans, but I could be wrong. If I don't find a vacuum leak or pulley issue this is probably where I'll turn to next since transmission work requires me to lift the car.

If its it changes with engine speed then it probably isn't the trans/diff...maybe a leak around your air box? That shouldn't cause rough idle but may be the cause of the noise.

I think this may be the issue now that I think about it because when I replaced the air filter, I noticed there were 2 or 3 screws missing from the box the air filter goes in and the plastic holding the treads for those screws was broken so I just superglued the treads in and added screws so the superglue may have failed, preventing the airbox from sealing correctly.

Ill inspect the airbox this weekend but I'll probably order another housing anyway since I'm pretty sure the superglue will fail sooner or later.

 

[brontosaurus]

http://www.youtube.com/watch?v=GK8WcfngXz0&feature=youtu.be

like that?

 

[. CrM .]

No, the sound I'm getting is a little bit different and not as audible. But this gives me the brilliant idea of trying to catch a recording of the sound, if my phone/camera will pick it up. I'll try to catch a recording of the sound tomorrow morning.

 

[. CrM .]

Well, it turns out that the sound was coming from one of my accessory belts instead of my aireebox. Nevertheless, thanks all for your advice(s)!