I have a 1991 240 wagon. There's a loud vacuum sound that comes from the center console that sounds like the vacuum tank filling with air every time I accelerate or leaving the tank when I shut off the car. At first I got scarred cause I thought it was the transmission. I didn't know there was a tank back there. I just recently got this car and never had a volvo before. I've never had a car make this noise. Is something in my vacuum system shot? or is this just normal?

 

There is a vacum reservoir that sits in the center console that runs all of the heater flapper valves in the dash. A vacum line runs from the intake manifold through the firewall and feeds this reservoir. Right on the intake manifold you will see there is a little plastic valve - I think it is black & white. Pull this valve off and blow through each end. If you can get air to flow both ways, then the valve is bad. Replacements are cheap and can be found on FCP Groton

I had this problem on several of my cars. Good luck.

 

You rock