im loosing coolent also. it can either be ur heater core. pump or many other things. if its ur pump. its gonna be a ***** to fix. put sore radiator stop leak in it and see what happens. if u still noticing leakage then u need to tear apart the front end and check it out

1990 Montero lwb, 3.0 V6, Custom bull bar, Completely stock on everything else. 186,000 miles
2" inch torsion bar lift. Conferr roof rack with homemade gutter mounts.