High pitch whine comes and goes above 30mph...

Bmachine

Bmachine

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Weird. Very high pitch for an old car (guessing between 3 and 8Khz...), does not seem to vary much with engine speed, comes and goes... Comes from engine bay. Too high pitch to be gear/transmission related... If I had to guess, it would be fuel injection related. Stock B35 motronic 1.3.

Any idea?
 
You say it doesn't vary much with engine speed.
An alternator could make a noise like that. May be a bearing?
Open the hood and get your hand on the throttle and rev it up and listen to see if it changes even slightly.

Update us when you can.
Gary
 
Thanks very much for the suggestions, guys.

A few more pieces of info:

- It only happens when I press on the accelerator. As soon as I release the accelerator it goes away.
- it only happens above 10 or 20 miles an hour. I cannot reproduce it without moving.
- it seems to happen mostly around 2500 or maybe 3000 RPMs
- It is not very loud at all. I would almost call it faint.
- It does vary with engine speed but very little. Although that could be because it is so high-pitched, it is harder to discern much variation.
- It is most likely not some thing like a bearing because it is too high-pitched. It is almost electronic sounding. The closest analogy I can come up with is, you know when you hit the rim of a crystal glass by flicking your fingernail at it. Imagine that sort of sound but continuous for a few seconds. Or like the sound you hear when your ears are ringing after a loud concert. Or after one of the ridicoulously loud Corvettes passes by your grandstand in an IMSA GTLM race.
 
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we once heard a strange high tune noise during a rally.... of course we were concerned it would came from the engine bay… till we found out it came from the little window … i could change the noise with more or less tension on the knob :)
 
Belgiumbarry said:
we once heard a strange high tune noise during a rally.... of course we were concerned it would came from the engine bay… till we found out it came from the little window … i could change the noise with more or less tension on the knob :)
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Thanks Barry, an interesting idea. Unfortunately that type of noise would be strictly based on car or wind speed. In this case it is not. Mostly on rpm range and accelerator status with car at speed. Also it stops instantly as I lift the throttle, before the wind speed has any chance to change very much. All of which makes me suspect something about the injection section.

I will test this out anyway of course. It would be awesome if it was that simple.

BTW, another bit of info is that it seems to come from the right front of the car, in the engine compartment.
 
Could it be a whistle sound? Air leak? I also had a 2002tii have a strange noise similar to yours and it was the distributor shaft so it could be lots of things.
 
dang said:
Could it be a whistle sound? Air leak? I also had a 2002tii have a strange noise similar to yours and it was the distributor shaft so it could be lots of things.
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It could possibly be that. Stevehose's suggestion of an exhaust manifold leak goes in that direction as well. But if that was the case, it would happen when revving the motor with the car sitting as well. But I only hear it when it is moving. I will double check all that this weekend though.

Maybe I should try to record it and post it here...
 
Bmachine said:
Stevehose's suggestion of an exhaust manifold leak goes in that direction as well. But if that was the case, it would happen when revving the motor with the car sitting as well.
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Not necessarily, revving the engine without any load won't create as much pressure in the exhaust as when it's under load, so it's possible that a sliiightly leaking manifold would only be noticed while driving.
I've heard some very strange noises coming from cracked/leaking manifolds, so I would check that out closely.
 
Gransin said:
Not necessarily, revving the engine without any load won't create as much pressure in the exhaust as when it's under load, so it's possible that a sliiightly leaking manifold would only be noticed while driving.
I've heard some very strange noises coming from cracked/leaking manifolds, so I would check that out closely.
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Definitely a possibility. Will check that as well.
 
I have no additional suggestions, but am on the edge of my seat following along with the theories (and eventual test results). Good luck, Bo!
 
Hey Bo. These are all great suggestions, and I hope you solve it soon and report back. But I wonder, could this be the "Call your Mother" alarm that sometimes goes off in our heads when we are just about to take off on a tour or vacation or similar? Just wondering. :rolleyes: Mike
 
All great suggestions, thank you.

After driving with the windows open I am not so sure it’s coming from the engine compartment anymore. It could actually be from the right center or right rear. The differential possibility is intriguing. Because it only happens for a few seconds when I accelerate, regardless of the gear. End it starts about half a second or a second after I start pressing on the accelerator. So at that point there is a load on the differential, so that would make sense. The only thing that doesn’t add up is that it is it is such a high-pitched whine, almost more like a whistle. Also, if it was the differential I would hear it coming from both sides. But in this case it’s only on the right side.
 
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