These are the possible causes of overheating listed in Haynes Repair Manual #36071; 1994 - 2005 Mazda B-Series Pickups: (1)insufficient coolant in system; (2)waterpump drivebelt defective or not adjusted properly; (3)radiator core blocked or radiator grille dirty and restricyed; (4)thermostat faulty; (5)fan blades broken or cracjed; (6)radiator cap not maintaining proper pressure - have the cap pressure tested by gas station or repair shop. Engine overheating can be caused by one of several problems: Sticking thermostat, if that's the case, replace the thermostat. Low coolant level, add coolant to solve that problem. Blocked or plugged radiator, radiators can build sediment and sludge and eventually get to the point that coolant doesn't flow through, causing the engine to overheat. Corroded or worn water pump blades, replacing the water pump cures that problem. Cracked block, head or blown head gasket, typically caused by prior overheating (see the above reasons) which caused the damage to the engine. If the head or block is cracked there isn't much you can do except to replace the failed part. If the head gasket has blown it's typically because the head warped while the engine was hot and a warped head does not provide enough even pressure against the gasket to keep it from blowing out the side. Just a very small amount of head warping will cause the gasket to blow out. A warped head can be machined and it will be as good as new. A blown head gasket allows exhaust gas under extreme pressure to release into the cooling jacket of the engine. When that happens, there is quite a bit of pressure that blows the coolant out of the engine and the engine will overheat because of insufficient coolant. I hope that's not your problem. Thermostats and water pumps are easier to replace.