You should be fine. The Volvo coolant has some nice features. It supposedly won't damage paint, has some very good pH balancers, and manages with hard water very well. However, many on this board have used other coolants for many years without problem...the key is to change it every 2 years. So if I were in your situation I would fill it up with some brand name coolant mixed 50-50 with distilled water. Naturally, you'll want to watch things closely as you might have some sort of leak.

-Ted