Just did a master cylinder on my '87 wagon. Those symptoms sound just about right. I got a master cylinder with reservoir from Roy Rogers (local foreign car parts store) for about 40 bucks. Great deal, the two different cylinders are different by how the lines exit the cylinder. Some have a line on each side and mine has lines on the right side. Noticed that my '81 has same cylinder, so your '83 probably has some one also. Easy job, the swap took all of 15 minutes, getting a wrench in there is the only weird part, tight movement, and lots of thread. The piston was too tough for me to push with my finger, so I just bolted the thing on, didn't hook up the lines and had asst. pump brakes while I held rag to catch squirting fluid, when no bubbles came out all was well, I hooked up lines, and all went well. I went ahead and bled the brakes anyway, I don't think it was totally necessary though. Good luck.
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1981 Volvo 244 GL w/ 225K Original B21F and 3spd. auto