Ihave an 89 3.9L and I can barely drive 20km without the truck almost overheating. I've changed the thermostat and water pump and tried running without the thermostat and nothing seems to help. Theres no oil in the coolant or leaks. I hope someone can help me!

try flushing the cooling system, if that doesn't work, check your fan clutch relay.

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'95 Dodge Dakota 4x4 5.2L club cab - 224kmi - Dual Exhaust, Filtercharger, Duals, sh--load of lights
'92 Dodge Dakota 4x4 3.9L club cab - 166kmi - V8 TB, '95 grand Cherokee Self-Dimming mirror - soon to have new exhaust

replace the radiator cap, if your system doesnt hold pressure it will overheat.

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trucks are fun =]

Ihad the same problem and did just what you did, no luck.My radiator from the engine side looked fine butI have A/C so could not see the front side behind the A/C condenser coil. I took the radiator out and the front side was all but gone, the fins all eaten away. Installed a new one problem fixed.