Before you proceed for the long haul, drive your car continously for an hour or two, in and around the city. If the car behaves well and you feel confident, only then go for it.
Plan your move meticlously. If going by Zhob side, plan a night stay at Zhob or DIK. If going by Sibbi, stop at Sukkur or RYK. Don't be ambitious in reaching destination.
Buy a good radiator flush, and use it. There are many a reasonable shops on Double rd, Airport rd and Jinnah rd.
Hope it helps