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240 Help identifying a sound behind center console

vanhoozj

New member
Joined
Nov 9, 2017
Location
North Carolina
I?ve got an 86 240 that is making a noise from behind the center console by the center vents. I?m not sure it?s the blower motor but wanted to see if anyone here has had a similar experience before I go that route.

To me it?s sounds more electrical vs mechanical; like the dull spinning noise of a motor being turned by hand almost a grinding or growling kind of thing. The sound begins when I am up to roughly 20-25 mph and air is coming through the vents even with the blower in the off position. I know airflow in the off position is partially by design with the A/C system.

The noise increases in speed as I accelerate and airflow through the vents also slightly increases. The noise goes away when the car is at a slow enough speed and airflow decreases as I decelerate. Once stopped there is no air flowing through the vents and no noise, again all of this is while the blower is in the off position.

The blower fan works in all positions and has no effect on the sound. I?ve pressed in the recirc button to attempt to eliminate airflow into the air box from the cowl and it doesn?t affect the sound either. The noise remains both while recirc is engaged or disengaged.

My initial thought was that somehow air is passing through the firewall and spinning one or both of the impeller fans causing the motor to rotate; therefore, making the noise. I can?t see anywhere that air is getting into the firewall as all the grommets look intact and sound.

I?ve also checked for exhaust leaks as a trusted mechanic suggested. The car has a larger exhaust than stock and a larger cat, but no luck isolating the noise to a leak.

Another mechanic simply said it's the blower motor but the motor operates fine at all speeds, no noise when I?m idling or under 20mph and this noise occurs even with the blower in the off position again at higher speeds so I?m just not sure that?s the issue.

Any suggestions?
 
Is the A/C knob FULLY turned Counter Clockwise? You damn near need to use pliers to get it to it's full OFF position.
 
From the passenger footwell, take off the center console side cover, stick your head all the way forward and, with a flashlight, look above the tunnel at the front of the air box. You should see the big recirc flap. At idle, push/pop the recirc button and see if the flap moves. From your description, I'm wondering if you have a vacuum leak and the recirc flap is staying in the no-vacuum recirc/opened position.

Even so, I'm not sure how this would be related to the noises. As a different experiment, you could tape over the cowl vent, or stick a sheet of cardboard under the hood, across the cowl, and tape it to the windshield, then go for a drive and see if the noises are different.
 
Thanks for all the suggestions. I've determined the noise is in fact not coming from behind the center console. Kind of tough to determine while driving alone but the noise is actually coming from an area near the shifter perhaps underneath the car.

I have tried the following: I took out fuse number 3 to attempt to eliminate the blower motor to rule that out. I've also covered the cowl vents to ensure the blend door/flap wasn't allowing any outside air into the car. The noise was present during these experiments.

Let me try to clarify what is happening. For reference it's an M46 transmission. At speeds over 15-20 mph, it makes this weird whining or whirring noise. It seems to come from the shifter area of the car. As soon as my speed drops below 15 mph, it instantly stops. The frequency of the whirring doesn't seem to change with speed, but it does seem louder/more obnoxious at lower speeds around town or when driving over 50 mph in 4th gear. Maybe I can just hear it better at lower speeds due to less road noise?

It makes the noise regardless if I've been driving for a while or just beginning from a cold start. The noise does not change even if I push the clutch in and take the car out of gear while driving down the road. Applying the brakes also has no effect on the noise, neither does turning hard in either direction.

Here is the one caveat, if I engage the overdrive button (5th gear) the noise seems to be less audible and at times appears to go away almost altogether. If I push in the clutch and go directly from 5th to neutral and coast the noise is the loudest at that time.

I replaced the driveshaft support bearing a couple weeks ago and it didn't resolve the issue. Any other suggestions are greatly appreciated.

Thanks
 
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How were the ujoints when you replaced the driveshaft bearing? They can make weird noises like that when dry inside. A ujoint may not have play but if it's dry insdie and it's the type you can't grease. Then it's bad.
 
The ujoints looked and seem to be good. I have no noticeable vibrations or squeaking noises and the car shifts fine in all gears.

Thanks
 
Here is the one caveat, if I engage the overdrive button (5th gear) the noise seems to be less audible and at times appears to go away almost altogether. If I push in the clutch and go directly from 5th to neutral and coast the noise is the loudest at that time.
That is a very important clue. Since you are able to change the sound at will by shifting in/out of OD, I'd focus on the OD unit. What is the history of the tranny?
 
Agreed that the OD could be the area to focus. The OD was rebuilt a few years back by a trusted Volvo mechanic for the previous owner. There is no documented history of any issues or changes to the transmission based on the service records.
 
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