Weird pitch sound

So I have a 2000 Tacoma. Its making a humming sound that seems to change pitch when accelerating. The pitch rises with accelerating and falls when letting off the gas. It is always present. It is not coming from inside the cab. I can hear it coming off the engine with the hood up or underneath the truck.

Any Thoughts?

 

ive been hearing the same noise in my 99 for months. its probably from old age i have 208k. did the noise just start?

 

Pop the hood, start it up, and try to locate the source of the noise.

 

Need more info. For all we know it's the normal operation of the engine. Does it vibrate, squeal, or just hum?

 

I have some kind of chirping noise at high speeds... It almost sounds like there is air in my coolant line not sure what it is tho.

 

Another another noise has developed.

1st noise: this one is been happening for a couple weeks. It's a constant whining sound. Coming from the engine but not distinct to either side or top or bottom. As I rev the engine either in gear or in neutral the pitch of the whining rises and falls with the RPMs. It sounds much like the normal operation of the engine when he rev it. However it's a distinct new sound. I'm worried it's the gearbox? I had a buddy do the clutch about four months ago. Besides that the engine hasn't been worked on ever save oil changes and standard maintenance.

2nd noise: this one is only been happening for a few days. At a certain high rpm a rattling sound occurs. I open the hood and hear it coming from the AC compressor unit when it's revved high enough. This also happens weather in gear on the freeway or revving it neutral. Wondering if it's time for a new compressor or an adjustment to the belts? Maybe a bearing going out?

 

250k on it by the way.

 

Not sure what else your ac belt goes to but if it's ONLY the ac you could try to take the belt off and if the noise stops you know it's the ac. Not sure how helpful that is but it's just a suggestion.

 

Does that first noise change when you step on the clutch? If so, then that would indicate a bad clutch release (throw-out) bearing.

You haven't mentioned what motor you have. It could be the timing chain noise from starting to wear out or maybe the guides (if you have the 3RZ).

 

I have a 2000 Tacoma sr5. 2.4 L engine. The pitch of the first noise falls when i push the clutch in but it never stops completely. I Did replace the throwout bearing when I did the clutch about three months ago. I may try to take the belt off the AC unit to check that noise thanks.

 

What was the problem? I'm having pretty much the same problem. 5 spd xmission? Mine hums like its another enging out running near me, at highway speeds. Really rev's up when I'm down shifting. Put in nuetral to a rolling stop and the sounds slowly goes away. Don't know what to think. 1995 204K miles. Never any work done on clutch or and xmissions parts.
I almost wonder if it's the front diff. as it is 4wd. I can't pinpoint it.

 

Center bearing was shot and also found rear u-joint slightly binding in spots. Repaired both at home and no more noise/vibe/hum.
Went with Dorman center bearing and Moog u-joint...both at Advance Auto. Total under $80. DM

 

Maticus (OP)

Any progress in locating the noise? Did you remove the A/C belt to see if it made any difference?

 

Turns out the noise was coming from a few of the pullys in the drivebelt. I had to replace both the drivebelt tensioner pully and the Idler pully. All back to normal. Much cheaper than I had thought it would be.

 

Thanx for posting the final solution. This is a pretty common occurrence. I already have spares for when it will, inevitably, happen to me.