Cooling System Bleed Plug Jeep 4.7 Engine

2002 Jeep Grand CherokeeMy 2002 Jeep Grand Cherokee with a 4.7L engine is over heating, I don’t think my coolant is going through my motor??? The air never gets warm it stays cold. I’ve changed out the water pump and thermostat, no change.


The most common reason would be form being low on coolant that may be from not bleeding the cooling system properly. Locate the cooling system bleed plug. Failure to purge air from the cooling system can result in an overheating condition and severe engine damage.

Cooling System Bleed Plug – Bleeding

  1. Tighten the radiator draincock and the cylinder drain plugs if removed.
  2. Remove the cooling system bleed plug from the upper radiator hose inlet housing (see Fig. 1)
  3. Fill cooling system with 50/50 mixture of coolant and low mineral water content until coolant begins coming out of the cooling system bleed hole. Install the cooling system bleed plug. Fill radiator to top and install radiator cap. Add sufficient coolant to the overflow tank till it reaches the FULL mark.
  4. With the heater control unit in the HEAT position, operate the engine with radiator cap in place. After engine has reached normal operating temperature, shut engine off and allow to cool. When engine is cooling down, coolant will be drawn into the radiator from the overflow tank.
  5. Add coolant to the overflow tank as needed. Only add coolant to the overflow tank when the engine is cold. Coolant level will be higher when the engine is warm due to thermal expansion. To purge the cooling system of all air, this heat up/cool down cycle (adding coolant to cold engine) must be repeated three times. Add necessary coolant to raise tank level to the FULL mark after each cool down period.

cooling system bleed plug jeep grand cherokee 4.7L engine

The engine overheating may be from being low on coolant and if it is not, It may be from the cooling fans not coming on if electronic or failed clutch fan assembly. As for warm air not coming out the dash, it may be caused by a clogged heater core or an issue with the ventilation system such as a failing blend door actuator. Failed Actuators are common on Chrysler products.

The blend door for all models is actuated by an electric actuator, while the AZC system uses 2 separate actuators to allow the driver and passenger to select individual comfort levels.

The mode door actuators for vehicles equipped with the standard equipment manual temperature control system are vacuum controlled. The optional Automatic Zone Control (AZC) system uses electric motors to actuate all mode doors. The service procedures for both types of actuators are covered by the following procedures.

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