Electric interference noise

[JungleGus]

I've been trying to diagnose this one for a while but am a bit stuck - on my M52 swap, I have a high pitched whine that sounds like electric interference (rising with revs, etc). Super annoying.

I've replaced at least one of the earth straps (if not both, struggling to remember) as one was shot, but the issue persists. As far as I know I'm using the DanThe loom

Any ideas? Electrics aren't my forte...

Cheers,
Gus

[Brianmoooore]

Do you mean the whine is coming from your 'speakers? If so, run the engine for 30 seconds with the serpentine belt removed, and see if it's gone.
Make sure you know how the belt runs before you remove it, and replace it so that it turns in the same direction.

[JungleGus]

From what I can tell, I THINK so - hard to be 100% sure. It's like a high pitched whistling sound.

Assuming that will stop all the accessories running and give me an idea if it's related to them or the engine itself?

[Brianmoooore]

I THINK so - hard to be 100% sure. It's like a high pitched whistling sound.

Turning the radio off should be fairly simple and quite conclusive!

[JungleGus]

Ah - it still makes the noise with the radio off (I was thinking speaker interference could occur without the radio on, but I'm probably wrong!) but I'll double check once I have her off jack stands

Simple test...=)

[fixedwheelnut]

Might be worth just undoing the oil filler cap a little and see if the crankcase has excessive vacumn? The cyclone breathers split on those engines causing excess vacumn in the crankcase causing a high pitch whistle usually air being sucked in via the seals.

Listen around the engine with a piece of fuel hose to pin point where the noise is coming from

[JungleGus]

Definitely not the speakers, will try check the belt tomorrow (prob not a bad idea anyway) and have a more in depth listen.

[JungleGus]

So - with the belt off, the noise SEEMS to have stopped but it's tough to tell without being in the car adn driving it - there is a little bit of play in the tensioner pulley and the water pump pulley but nothing too bad...do you think these need to be replaced?

The noise still seems electronic in nature, even though the stereo is off.

Conundrums...

[Brianmoooore]

Do you have an OBC?
Are the tensioners noisy when you spin them?

[JungleGus]

I do - the 13 button one

The tensioner (is there multiple?) didn't seem noisy, just slightly looser than a new ball bearing should feel

[Brianmoooore]

Check out the OBC gong, mounted in the panel above the driver's knees. The gong consists of a constantly running tone generator, which you can't hear because the volume is (electronically) turned to zero, except for the brief period when the gong sound is triggered.
If a fault occurs with this electronic volume control, the continuous tone can 'break through' at low level.

[JungleGus]

Will check out tonight, thank you!

[ChrisHC]

A high-pitched super annoying whine, worse when the revs rise? Check for mother-in-law in the back seat!