Hum while stopped in drive

[shunt]

Hi there,

Anyone else have a dull hum while stopped at a stop sign or red light? Hard to tell where it's coming from, sounds sometimes like behind the driver's seat, sometime near the transmission. Sometimes softer, sometimes elevates, sometimes not at all. Switching to neutral makes it go away, sometimes only for a few seconds.

Any suggestions on the diagnosis, or where to start looking? By the way, definitely not the radio

Thanks!

[Disco Mike]

You need to get a lot more specific as to where, when and the sound.

[shunt]

Hi Mike, happy 4th!

It happens while the car is stopped and in gear (stop sign, red light). Shifting to neutral makes it go for a bit, about 50% of the time it will hum again while in neutral.

It seems like the hum is coming from under the passenger seat behind the driver. Occasionally, it sounds like it's coming from the area near where the transmission meets the engine... hard to tell.

Doesn't happen right away when I turn the car on... takes a few minutes. And funny enough, when I have the time to get out and try to listen under the car, it coincidentally won't reproduce.

Not super loud, not an interior part vibration.

Any ideas?

[Disco Mike]

What year is it and where do you hear the noise coming from? Could be the SAI air pump kicking on.

[bguetter]

Sounds like SAI

[Mr. Fitch]

try messing with the ac speed sometimes the fan has that effect

[Tim the Enchanter]

What you describe sound very similar to what I had on my DI. Locating the source was absolutely maddening. I finally got rid of the hum after checking the fuel pressure regulator with a vac pump and blowing the return line out with compressed air. I'm pretty sure the noise was actually the regulator vibrating the return line. I gave the regulator 15" of vac to test the diaphram and no more hum after that.

[shunt]

Thanks everyone for the suggestions. Tim, I don't know if that's it, but I'm definitely going to check that out. It's a tip like this - an obscure craziness - that makes this forum so valuable.

[ppieczul]

I am having exactly same symptoms on my 2000 d2. Wondering what was the end of your case since this was the only one I found on the Internet that matched so well with mine. Appreciate your help.

[Disco Mike]

Next time start your own thread instead of a near 2.5 year old one. On your thread, tell us exactly your truck is doing, how long it doing it, what have you checked and the mileage of your Disco. Would help us help you.