whine under air cleaner box

[stevepaa]

I did a search for whine and nothing relevant turned up.
Just this morning a new noise began. It is a rather high pitched whine coming from the silver module located down below air cleaner box.
Anyone know what is is?
thanks

2007 xc70

[hoonk]

high pitched whine coming from the silver module located down below air cleaner box.

That is your vacuum pump - if it is running all the time the vacuum switch that controls it is probably broken. You might want to disconnect the pump before it overheats and melts....

It will be harder to stop the car when first started without a working vacuum pump.

[stevepaa]

what is the vacuum pump for, the brake booster? why not just pull vac like other cars?
i found the vacuum pump in VADIS. where is the switch? thanks

my vadis only goes to 2005, is there a version for my2007

found it. not quite where wiring diagram puts it

as the switch is a direct feed from CEM fuse 33, switch must be faulty, disconnect switch and then reconnect and pump is off for now, I will get new one . thanks

[hoonk]

what is the vacuum pump for, the brake booster? why not just pull vac like other cars?

Yes the vacuum pump is only for the power brakes -

I think all the cars with variable timing on the intake cam have a vacuum pump. Perhaps the intake cam timing at idle does not produce enough vacuum.

[vtl]

Yes the vacuum pump is only for the power brakes -

I think all the cars with variable timing on the intake cam have a vacuum pump. Perhaps the intake cam timing at idle does not produce enough vacuum.

Nope, B5244S does not have the pump. I'd say, cars with turbo have the pump.

[JRL]

Turbo cars have a pump, ALL makes, all models

[hoonk]

There is not one on my 2001 and 02 US xc70. (both don't have variable timing on the intake either)

[MacNoob]

The pump is there because whenever a turbo is under boost, there is no engine vacuum to assist the brakes. Not all cars with turbos have a pump, assuming that you're not under boost continually you regain vacuum as soon as you let off the gas.