1996 dodge ram. Vehicle runs hot. I have replaced water pump, thermostat, coolant temperture switch , clutch fan. checked radiator for flowing properly also had block tested for blown head gasket.

Sounds like either a bad head gasket, cracked head, or block. Also you may want to go to a shop and have them check the transmission and radiator coolant lines. You could have trans fluid getting into your coolant.

Have you run it with cap off and full to watch for flow when thermostat opens? WIth heater on as well, to bleed system properly. If your not seeing the flow at normal operating temperature when thermostat should be, or is opening, then you probably have a water pump problem.

You didn't state when it overheats, if it is while driving the fault can be : belt driving water pump slipping , lower radiator hose collapsing, most common is clogged radiator. Start the engine with the radiator cap off when it is COLD and observe the flow in side. If you see really fast flow of coolant you have the bottom portion of the radiator stopped up. The only way to know is to remove the radiator and have it flow tested.
A blown head gasket or cracked head will cause steam to come out of the exhaust, water in the oil (milky). If it is running hot while idling , check fan to see if it is turning as it should when it should. Older cars have fan clutches that go bad, newer ones have temp thermostats that go bad.

Have you checked out the water pump? Most of the time, you can feel movement in the /head shaft area before it fails. Water pumps usually go slowly, pumping less and less water (making the engine run hotter). The also get noisy when they start to fail.

that what fan suppose to do.when engine coolant temperature rise to 190 - 220 degrees the coolant fan will run cooling engine down to 180 degrees.

Overheating can seriously damage a car's engine if left unchecked. Although overheating simply means that a car's engine temperature exceeds normal operating temperatures, the causes of overheating are varied. What follows is a brief list of some of the most common causes of engine overheating.

Faulty Radiator
1. A car that overheats will often have a faulty radiator. A radiator is responsible for cooling hot engine coolant that picks up heat from inside a car's running engine. A radiator "radiates" the heat from engine coolant out into the outside air. A faulty radiator loses its "radiating" effects and allows engine coolant to become overheated, thus rendering it ineffective at adequately cooling and engine.
Faulty Water Pump
2. A faulty or malfunctioning water pump prevents adequate engine coolant flow and can cause a car to overheat. A water pump serves to pressurize and propel engine coolant throughout a car's engine and radiator to increase the heat-reducing capabilities of engine coolant. A faulty water pump loses its ability to adequately pump and propel engine coolant, and can cause a car to overheat.
Coolant System Leaks
3. A leaky engine coolant system reduces the level of circulating engine coolant, which increases engine temperature and leads to engine overheating. Radiators, water pumps, and coolant system hoses and seals--all of these coolant system parts can develop leaks, which can result in low coolant levels and engine overheating.
Faulty Thermostat
4. A car thermostat regulates the flow of engine coolant. A thermostat is a heat-sensitive valve that opens when a car engine reaches a set operating temperature and closes when a car engine is cold and warming up. If a thermostat gets stuck in the closed position, coolant will be prevented from reaching the engine, which will quickly lead to engine overheating and potential engine damage.
Low Engine Oil Level
5. Engine oil, in addition to lubricating an engine's internal parts, helps to keep engine operating temperatures reduced by eliminating friction within the engine. If engine oil levels are low, friction and heat build up inside an engine, a condition that causes increased engine operating temperatures and can lead to engine overheating.

Ihave a 2000 Dodge Durango i have put a new radiator and the gaskets came back good um i replaced the coolen fan also the thermostate and tested it it it came back good when i run it its fine but when i am in line its hot when i drive it cools down........

The only item left that controls the flow of the coolant is the thermostat. It is and usually replaced with the water pump or radiator because it is an inexpensive part. The thermostat blocks the flow of coolant until the vehicle warms up to the thermostats specified temperate recommended by the vehicle manufacture then opens to allow flow of coolant.

You may need to replace the thermostat or water pump, even flush out the system. Best thing to do is to flush out the system with radiator flush and follow the instructions and replace the oil antifreeze with new one with a 50/50 mix (water/antifreeze), if you not sure how to do that you can buy them premixed. Next is to replace the thermostat and radiator cap, that should fix the problem. The last thing would be the water pump is weak and would need to be replaced but lets start with the simple., The other thing to if it's only hot when your at a stop light then check the fuse and relays and wire harness to your radiator fan to make sure it's working. If you turn on your A/C that would over ride the temperature sensor and activate the fans so you know that is working, so if's running hot all the time even when your driving, replace the thermostat and coolant. Good luck.

Check the lower radiator hose to see if it has gone "soft" Check when the engine is cool and stopped, grasping the hose and giving it a squeeze, you should feel the presence of a "spring" in the hose. That should be there to prevent the hose from collapsing as the water pump draws coolant through it. Without the spring, the draw created by the pump intake, and the resulting venturi effect will collapse the hose, cutting off the flow.


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