I have a 91 b2600i 4x4 and I have flushed the radiator , changed the thermostat and it is still overheating doesn't seem to have blown head gasket . Engine only has about 13000 miles since overhaul . Any help appreciated . I am also having problems getting the 4x4 to engage seems to try to go in by itself sometimes I have to put in 4x4 and then out again while moving to keep it from grinding . When it does go in it will pop in the front end and then go ahead and work .

 

Does your water pump work? Take off the radiator cap (COLD engine), start the engine then rev it up, if the water gets sucked down then it works, this might be more difficult if the cap is not on the radiator itself but on an expansion tank.

 

One thing to start with, is it overheating, reading a guage should be verified unless it is blowing steam ect.