I have a forty year old house and the windows are in great condition however the aluminum spring loaded tracks nolonger seal properly at the bottom of several of the windows that are opened during the summer. (Unused windows are great no air seepage and they aren't sealed by paint).

Two questions:

1. Can I purchase new tracks, or somehow refurbish these?

 

Can you? Or should you? Those old style tracks always leaked air behind the tracks, there just stapled in place with nothing behind them to stop air from getting in.
Are they also wooden windows?
If there were mine I'd install replacement windows for an air tight seal, and 0 mainintance.

 

I removed my sashes and aluminum tracks and replaced with kits from Jeld-Wen. The kit includes new vinyl tracks and double pane, tilt-out sashes. The existing frame and jamb is left in place. Installation is about 30 minutes for each kit.

 

It's highly unlikely you would be able to find parts for 40 year old windows. What you probably CAN do is remove the sashes (they sound like they are the type that you open halfway, then push to one side to remove) and then unscrew the tracks on the side with the springs. You might possibly need to stretch the spring out if it's lost some of it's recoil. (some can be adjusted by how tight the adjusting screw is screwed back) But if the track is bent, it likely can't be repaired. You might try robbing parts from the windows you use less often, and put them on the windows you use most often.

If the window is cocking to one side, leaving a gap along one side, it could also be that the window is out of square, meaning the bottom of the sash might need to be shaved on one side so that it isn't cocking to the side when you shut and lock it. Bring the window sash closed and just before it closes, observe the gap of light between the sill and the bottom of the sash. That will give you a good idea of how much would need to be shaved off of which side. If you shut it a little more then scribe the interior with a pencil it would give you a reference line for how much wood to remove. Removing the sash and using a belt sander would probably work well for that.

 

Jambliners are readily available, though limited in styles and sizes. Where I used to live, many people lived in older homes and desired to keep the original windows...even when I suggested sash replacements or vinyl replacement windows. Some reglazed with double pane glass and repaired/replaced the balances. It's not as inexpensive or energy efficient as replacement sashes or windows...but it can be done.

Blaine Window hardware in MD was a very good resource when I was in VA. Helpful people as well.