recently my 1995 xg longreach has started making a strange humming noise that gets rather loud and extremely irritating when im driving.

the sound resembles that of a vacuum when you stand outside the house someone is vacuuming, the sound also changes slightly in pitch when I apply the brakes. This sound is there 24/7 when the engine is running and I have searched and searched for what is causing the noise but have failed to find anything it could be.

the noise can be heard very clearly in the cabin and in the tub but not at all if you pop the hood and listen there and the noise seems to be coming from under the car on the drivers side although in the cabin it sounds like it is passenger side, in desperate need of advice as taking it to the auto shop is always an expensive event and I would prefer not to have to do that.

I have run it on gas and on petrol and the noise stays the same on both of them.

if anyone has any information that might help at all I am at the point where im going to start removing panels so I can get better access to the mechanics as the noise is annoying me so much.

Maybe a stupid question: Have you ruled out exhaust leaks?

Ruled it out no but one of the joins in the exhaust system was rather loose...to the point it was almost falling out but that has been tightened I just have no idea how to check the rest of the exhaust systems I mean I have run my hand (while gloved) along the pipe while the car is running and no change in noise levels as far as I can tell I mean if it is leaking it is a very very small leak because I don't see any punchers in the pipe.

You can use a metre-long piece of hose (like garden hose) as a stethoscope. Hold one end to your ear, and run the other along the exhaust, engine bay, or anywhere else on the car you want to check. Works a treat.

i no longer think it is an exhaust leak as the sound changes slightly when i turn on the lights and when i apply the brake so could it possibly be the alternator? or something electrical as any time i turn on my headlights or my blinkers it changes slightly i didn't notice it before because i hadn't turned the lights on at idle after the car had been running for a while and wasn't paying attention when i used the blinkers.