A buddy has a 99' cherokee w/ a 4.0L. He has been having overheating problems. He called last week and said he replaced the thermostate (Cheap, easy try for him) and that did not do anything to help. I talked with him over the phone and asked him to fill the radiator and have some fire up the truck see if the level of coolant/water drops in the radiator. He said it didn't move. Next he pulled the return hose to the radiator and fired up the truck and nothing flowed out and he said there seemed to be no pressure. I'm assuming the pump is the problem, but I have not worked on a newer 4.0L and am not aware of the cooling system. Does this seem like the problem or does the motor build up heat before the pump kicks on? Have not actually seen the truck so am seeking some advice to pass on. Thanks in advance for any help.