Mystery smoke and noise from 240...

[SILVER97LE]

97 240sx -

With no rhythm or rhyme, my car will start making a loud humming noise and after probably 5 minutes with the noise, I start getting a relatively small amount of dark colored smoke. Then for no reason the noise will stop and the smoke/smell go away immediately. The noise and smoke are coming from the side of the engine with the battery / alternator. It is coming from the front of the engine. Unfortunately the fan makes figuring out exactly where the smoke is coming from impossible.

If I were to bet, I would say it's the alternator, but can it smoke? Could it be wires burning inside? I have never gotten a warning light for it.

Although it does have a oil like smell, it goes away immediately when the noise ends. Also, it is not the belts because they look perfect with no wear on them. I want to get it fixed, but it never does it when I near a place were I can take it in.

Other things - 1)Sometimes I will drive for 15 miles and the noise/smoke are still there, but sometimes it lasts only for a few minutes.2) It happens when the car is hot or cold.

Please give me some guidance on this one.

If I don't write back, it's because I died from smelling to much smoke while trying to figure out the problem.

[180fan]

look for melted wires.

[SILVER97LE]

There is nothing visibly wrong - no melted wires, residue, etc...

I just don't want to take the car in a have the guys start guessing and replacing random stuff.

Has anyone heard of the alternator smoking? And, what does an electrical burn smell like? Is it similar in smell to oil burning?

Something else I didn't mention before was that the noise increases with revs, so I know it is something belt driven. And it makes the noise with the A/C compressor on or off.

Isn't the alternator the only logical solution?

[SILVER97LE]

Is there really an online mechanic here?

[SILVER97LE]

For those who care, it was the the front main seal leaking oil on the belts. The oil caused the belts to slip on the pulleys causing the smoke every now and then.