Well i replaced the thermostat and housing radiator cap bypass the heating controller unit and the car keeps overheating whats the problem?

A possibility is the water pump. This is what circulates the water through the engine and back to the radiator for cooling. Water pumps consist of several vanes attached to a rotating shaft. If a few vanes are broken, you'll get reduced water circulation, causing overheating.

The coolant must operate under pressure to raise its boiling point (so it won't turn to steam.)

Replace the radiator cap with a new one.

You need to fill your antifreeze with the truck running and your heat on. You leave off the radiator cap and let the truck warm up. The cap is left off to bleed air out of the system. Once the truck reaches temp for the thermostat to open, your fluid level should drop about 3/4 gallon. Give that a try and see what happens.

Well, a thermostat could be an issue, look for leaks, pressure test the cooling system, as pressure helps keep vehicle from overheating. Thermostats get replaced, diagnostically. There are many components to overheating, the above tests should shed some insight to your issue.

A FAULTY THERMOSTAT STUCK OPEN WILL EFFECT GAS MILEAGE AND CAUSE POOR OR NO HEAT CONDITIONS.THERMOSTAT NOT A HARD JOB TO FIX.ALL YOU NEED TO DO IS DRAIN OUT SOME OF THE COOLANT IN A DRAIN PAN.DRAIN COOLANT LEVEL BELOW THERMOSTAT.IF YOU HAVE 3.8L ENGINE THERMOSTAT HOUSING ON TOP INTAKE MANIFOLD.IF YOU HAVE 5.3L ENGINE FOLLOW TOP RADIATOR HOSE IT WILL LEAD YOU TO THERMOSTAT HOUSING.REMOVE HOUSING THERMOSTAT INSIDE THE HOUSING.IF YOU HAVE WATER INLET ANDTHERMOSTAT IN ONE COMPLETE UNIT OR HOUSING YOU HAVE TO REPLACE THE ENTIRE WATER INLET HOUSING WITH NEW THERMOSTAT.THIS TYPE UNIT WILL HAVE LONG PIPE WITH BYPASS PIPE WITH WATER INLET WITH THERMOSTAT. ONCE YOU REPLACE THERMOSTAT.IF YOUR RED ARROWS OFF AND HEAT STILL DONT WORK THE DEALERSHIP WILL HAVE TO CHECK IT OUT.WITH NEW THERMOSTAT AND PRESSURE CAP.MAKE SURE GET COOLANT LEVEL CORRECT.SEE HOW HEAT WORKS.IF NOT YOU HAVE A ELECTRICAL PROBLEM AT AC AND HEATER CONTROL SWITCH.

Overheating can be numerous things: Fans not working, water pump, thermostat, overflow cap, and the list keeps going. When the engine is running and heats ups, feel the heat of the top hose, if the hose isn't hot, the thermostat is most likely stuck open and needs replaced. If it is hot we know you have circulation. The cap on the expansion tank may be defective, if it can't hold the pressure of the water, it will release at the overflow cap if the cap is bad. Also check the coolant level.

If you follow the upper radiator hose from the radiatior to the engine, it connects to the thermostat housing. The housing is where the thermostat is located and it is held inplace by a couple of bolts. It is easier to replace the thermostat if you drain most of the coolant out of the radiator. There is a valve on the bottom corner of the radiator. Also, for a few extra bucks, replace the radiator cap to make sure it is functioning properly, since it was over heated.

replace radiator cap system depends on good pressure to keep from overheating

After replacing the thermostat, you must bleed the air from the cooling system.

To bleed air from the 2.2L and 2.5L engines, remove the plug or sensor on the top of the thermostat housing. Fill the radiator with coolant until the coolant comes out the hole. Since the plug is made out of steel and the thermostat housing is aluminum, it is a good idea to apply an anti-seizing compound or Teflon® tape on the plug threads prior to installation. Install the plug and continue to fill the radiator. This will vent all trapped air from the engine.

Any trapped air in the heating system will have to be displaced by coolant. Once the cooling system is filled, with the radiator cap off, turn of the heater at it's highest setting. Start the engine and allow it to reach operating temp. You should see a drop in the coolant level as the air in the heating system is displaced by coolant. Add coolant to the proper level and replace the radiator cap.

Keep a close eye on the coolant level for at least the next couple of weeks. The cooling system is a "closed" system. Any significant decrease in coolant level indicates a problem.

If you have any questions, let me know.

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Drive safe and be warm.

clarkco

The first thing to do is have is the radiator cap checked, if it's alright then check to see if the thermostat is opening. You will need to remove the thermostat housing to remove it. The temperature the thermostat is suppose to open at is stamp on it. Heat a pan of water a few degrees above what it is suppose to open at and put the thermostat in to see if it opens,