Day before yesterday, I bought a '92 745T. great body, tired motor that runs pretty good, OK interior (very good interior except worn out front seats), really cheap. car has a coolant leak at the head gasket (dribbles a little externally when cold, there's no coolant in the oil or oil in the coolant) and the turbo is really oily on the outside, I'm assuming that I'm going to be doing a head gasket and new turbo at some point, but in the mean time its running fine. there's some kinda hissy sound under the car and a 'moan' comes and goes from under the passenger area at low speeds that is throttle dependent, I'm guessing its an exhaust leak of some sort and or funky turbo sounds, and figure on sorting that out while doing the head gasket etc.

Bringing it home, when I exceeded ~65MPH, a loud 'buzz' sound started up that seemed to be coming from the upper front of the passenger door. I shut off the stereo (cheezy aftermarket JVC hooked up to the OEM speakers), and the ventilation fan, and it didn't change. it didn't change frequency with speed or RPMs. it got a little louder at 70 and not any louder at higher speeds (at least up to 85, I didn't go over). Sounded like it was right around 60Hz, like a loud electrical buzz you might get from a piece of sheet metal near a big transformer. I reached across the car and poked at various things, nothing felt like it was vibration, nor did anything I did change the sound, including dropping the passenger side window and raising it, twinking with the passenger side mirror, etc. drop below 65 and the noise stopped. Also at one point, accelerating up a long grade at 70 also stopped the noise but it resumed at the top of the hill when I backed off.

yesterday I removed the passenger door panel, and thumped everything around it, nothing felt at all abnormal, the door panels are in really good shape as are the doors and seals. ditto I thumped all around the dashboard, underside kick panels, outside trim, etc, nothing felt loose or buzzy.

car history:
in the past few years, the PO had replaced the radiator, water pump, starter, all 4 brake rotors, lots of little stuff like all the exterior lights, all done by a one-man indie Volvo shop that has a very good reputation. It finally nickel-dimed her to death with this head gasket thing, hence her selling so cheap. I'm figuring on spending $2000 or so to bring the motor and turbo up to like-new, and another $1000 or so on tierods/bushings/etc that are tired, re-skin the seats, etc, and for about $5000 I get a really really nice car I can happily drive for 10+ years.

this is our 7th Volvo...

1. 87 240GL sedan, still with us, soon to be daughter's car
2. 89 780 Bertone V6, wrecked
3. 93 960 Wagon, totaled
4. 98 S90, blown motor
5. 96 850 Turbowagon, my current daily driver
6. 91 940SE wagon, son's car
7. 92 740 Turbo wagon, new daily driver

 

I have the same noise on my 940(are you sure our cars aren't fraternal twins?), howerever, my pass door panel is cracked and I found that's where mine is coming from... also check the trim around the inside door handle, as I've seen alot of these rattle as well.

 

the door handle trim is in perfect condition. anyways, I reached over and wiggled all that while it was buzzing wednesday night, including putting some pressure on the window switch, and the door lever as well as the trim, nada was the buzz.

I'll probably have to get someone to go drive me around, and its not always easy to find a stretch of highway that I can even GO 65+ on without having to drive 1/2 hour or more.

 

I may have found the source of my buzz.

the plastic trim above the front passenger door is broken near the forward attachment point of the handle. there were several bits of plastic of various sizes trapped up there. I bet one of those bits of plastic fell down the window pillar liner and is buzzing around at dashboard level when the resonances are right.

now I have to figure out how to remove that piece. it goes under the piece thats around the handgrip, and it goes down below the top of the dash, to about the top hinge. worse, this car has a replacement windshield, and the installer was really sloppy with the glue, its everywhere.

speaking of... whats the best way of removing that nasty black windshield goober stuff from glass, plastic, skin, shoes, and anything else it touches?

 

that was NOT the source of the buzz. I put gaffers tape over the windshield exterior trim on the passenger side pillar and it stopped. I tried removing the top tape, and usinig just tape on the bottom and it started again. Tonight, I tried just tape on the top 6" and it didn't do the Angry Bee thing once on a 120 mile round trip at mostly 70-75mph.

oddly that trim seems very solid, and not at all loose. I'm thinking of lifting the corner piece and squirting some clear RTV (aquarium sealer) under it, and seeing how that works, I dunno

 

It could be one of the clips that hold that mouldind down. It may be on solid but that doesn't mean that it is attached to all the clips. These clips often break and may be some vibration at speed that causes the noise... Pop off the moulding(s) and see-the clips are cheap-some of them will be broken or break when you do that.

To clean the sealant best is stuff like ether based carb cleaner... takes very little.