Hydraulic leaks on Belarus tractors is a very easy fix! The factory uses copper washer seals on the many banjo fittings in the system. Get ahold of some domestic washers that are made out of softer material and problem solved.
If the cooling fan belt is tight, and there is no clutter where the air passes through the cylinders, you can NOT over heat an air cooled Belarus. If it is well maintained, it will run very cool.