Volvo Repair: Volvo brakes, cylinder problem, master cylinder

Question
I'm sorry. After I sent my message I realized that I had forgotten to tell you the year and model, but your box was full.   It's a 1990 740 GL.  Thanks.
-------------------------------------------
The text above is a follow-up to ...

-----Question-----
My brake pedal is very soft and has to be pressed pretty far to the floor to get a good stop.  It feels a bit like there is air in the line, but it doesn't pump up when you press on it several times.  There is no screeching or grinding, don't see any leaks, and the fluid container is full.   My husband just opened up the wheel and looked at one set of brakes and thinks they aren't really too worn.  We were wondering if this could be a possible vacuum or master cylinder problem.  Would prefer to ask ahead before going forward with replacing disks.
-----Answer-----
Vicki, would help if you told me what year and model car you have.  Roger

Answer
Vicki, these models can get picky sometimes.  I would say replace the master cylinder and be done with it but its best to put the car on a lift and see if there is anything leaking like perhaps a junction block or one on the calipers may be leaking.  If all is nice and dry, then I would try bleeding the brake system first and then if no luck then spend the money on the Master cylinder.  Roger