DESCRIPTION
Basic liquid cooling systems consist of radiator, water pump, thermostat, cooling fan, pressure cap, heater and various connecting hoses and cooling passages in block and cylinder head. Many vehicles use clutching fan, which may incorporate thermostatic control, or flexible blade fan, or both to reduce noise and power requirements at high engine speeds.
Some models use thermoswitch located in radiator tank to activate electric cooling fan(s). This system is usually found on vehicles with transversely mounted engines. Due to exhaust emission control, some vehicles use thermostatic vacuum switch to advance ignition timing in case of overheating.
As most new models require use of permanent, year-round (ethylene glycol) type antifreeze, coolant recovery systems are being used more commonly to prevent coolant loss. Requirements for antifreeze have changed due to materials used in engine manufacture.
DRAINING
Remove radiator cap and open heater control valve to maximum heat position. Open drain petcocks or remove plugs in bottom of radiator and in engine block. In-line engines usually have 1 plug or petcock, while V-engines will have one for each bank of cylinders.
CLEANING
Good cleaning compound will remove most rust and scale. Follow manufacturer's instructions in use of cleaner. If considerable rust and scale have to be removed, flushing will be necessary. Clean radiator air passages by blowing out with compressed air from back to front of radiator.
FLUSHING
- Back flushing is very effective procedure for removing rust and scale from cooling system. For best results radiator, engine and heater core should be flushed separately.
- To flush radiator, connect a flushing gun to water outlet of radiator and disconnect water inlet hose. Use leadaway hose, connected to radiator inlet, to prevent flooding engine. Use air in short bursts only, as clogged radiator could be easily damaged. Continue flushing until water runs clear.
- To flush engine, first remove thermostat and reinstall housing. Connect flushing gun to water outlet of engine. Disconnect heater hoses from engine. Flush using short air bursts until water runs clean. Flush heater core as described for radiator. Make sure heater valve is opened to maximum heat position before flushing heater.
REFILLING
Engine should be running while refilling cooling system to prevent air from being trapped in engine block. After system is full, continue running engine until thermostat is open, then recheck fill level. DO NOT overfill system. Refer to COOLANT SPECIFICATIONS table.
| Application | Qts. (L) |
|---|---|
| 2.2L | 9.0 (8.5) |
| 2.5L | 9.0 (8.5) |
| 5.2L | 15.5 (14.6) |
COOLANT SPECIFICATIONS
Scheme 1
- Visually inspect thermostat for corrosion and propersealing. If satisfactory, suspend thermostat and thermometer in container of water. Do not allow either thermostat or thermometer to touch bottom of container as concentration of heat could cause an incorrect reading.
- Heat water until thermostat just begins to open. Note temperature at which thermostat begins to open. Compare to specification in table. See «COOLANT SPECIFICATIONS»(/dodge/ram-van/ii-1979-1993/remont/cooling-fan/#engine-cooling-fan) table. Replace thermostat if it does not open. (Scheme 1): Testing Thermostat NOTE: Thermostat should open as water is heated. NOTE: Some models use plastic or aluminum components in radiators. Ensure proper cleaning solution is used.
PRESSURE TESTING RADIATOR CAP
Visually inspect radiator cap. Dip cap in water and connect to tester. Pump tester to bring pressure to upper limit of cap specification. Refer to COOLANT SPECIFICATIONS table. If cap fails to hold pressure within specified range, replace cap.
Testing Radiator Pressure Cap. Scheme 2
Note. Attach cap to tester and apply correct pressure.
PRESSURE TESTING COOLING SYSTEM
- With engine stopped, wipe radiator filler neck seat clean. Fill radiator to correct level. Attach cooling system tester to radiator and pump until pressure is at upper level of radiator rating. If pressure drops, inspect for external leaks. If no external leaks are evident, start engine and run with tester attached. NOTE: Pressure may build up quickly. Release any pressure above limit of pressure cap specifications or cooling system damage may result.
- Extremely rapid buildup of pressure may indicate combustion leak into cooling system. Check for water at tailpipe. Excessive water could indicate faulty head gasket, cracked block or cylinder head near exhaust ports. Remove oil dipstick and if water globules appear in oil, serious internal leak is indicated.
ANTI-FREEZE CONCENTRATION
Test anti-freeze concentration. Tester should have temperature compensating feature. Failure to take temperature into consideration could cause an error as large as 30°F in freeze or overheating protection. Follow manufacturer's instructions for correct use of tester.
Pressure Testing Cooling System. Scheme 3
Radiator cap consists of pressure valve and vacuum valve. Cap has several different functions: preventing coolant loss when vehicle is in motion; preventing impurities from entering cooling system to minimize corrosion; allowing atmospheric pressure to eliminate vacuum that occurs in system during engine cooling period; and raising coolant boiling point approximately 3°F (1.6°C) per psi increase by maintaining constant cooling system pressure. See COOLANT SPECIFICATIONS table.
Radiator Cap Operation. Scheme 4
Note. Cap should maintain constant pressure in cooling system.
Coolant recovery systems differ from normal cooling systems in that an overflow bottle is connected to radiator overflow hose. Overflow bottle is transparent or translucent to permit checking of coolant level without removing radiator cap. No adjustment or test is required beyond keeping vent hole or hose clean and checking pressure relief of radiator cap.
OPERATION
As coolant temperature rises and pressure in system exceeds pressure relief valve of radiator cap, excess coolant flows into overflow bottle. As engine cools and coolant contracts, vacuum is formed in system, drawing coolant, stored in overflow bottle, back into radiator. In properly maintained cooling system, only coolant loss will be through evaporation.
Coolant Recovery System. Scheme 5
Note. System should minimize loss of coolant.
This unit consists of thermostatically controlled fluid fan drive (torque control clutch). Thermal control drive is silicone filled coupling connecting fan to fan pulley. Drive is operated by control valve. Control valve is governed by temperature sensitive bimetal coil or strip. Control valve maintains flow of silicone through drive.
During periods of operation when radiator discharge air temperature is low, fan drive limits fan speed. High radiator discharge air temperature causes bimetal to allow greater flow of silicone to enter drive. This increases drag between driven member and driving member, resulting in higher fan speed and increased cooling.
Scheme 6
- When engine overheating or insufficient cooling by air conditioning occur, fan drive and thermostatic control must be tested. Start with cool engine to ensure complete fan drive disengagement. Cover radiator grille sufficiently to induce high engine temperature.
- Start engine. Operate at 2000 RPM and turn on air conditioning, if equipped. Fan noise will increase when fan drive engages. It will take 5-10 minutes for fan to become engaged. While operating engine under these conditions, observe temperature light to prevent overheating. If hot light comes on, remove cover from radiator grille.
- As soon as drive engages, remove radiator grille cover and turn air conditioning off to assist in engine cooling. After several minutes fan drive should disengage. This can be determined by reduction in fan speed and noise. If fan drive fails to function as described, it should be replaced.
- Fan drive should also be replaced if shaft seal is leaking fluid. If noise or roughness can be felt while turning by hand, replace drive. Frozen unit must be replaced. Blade tip rock of more than 1/4" front to rear indicates worn drive unit which should be replaced. (Scheme 6): Thermal Control Fan Drive Unit NOTE: Rotation speed will vary with engine temperature.
This unit is same as thermostatically controlled fan drive except it is not controlled by bimetallic (temperature sensitive) coil. Fan drive allows fan to be driven in normal manner at low speeds while higher engine speed limits rotational speed of fan to predetermined rate. Silicone in drive housing provides more positive drive at lower speeds and allows greater slippage between driven member and driving member at higher engine speeds.
TESTING
In case of engine overheating during low speed or idle operation, increase engine speed to approximately 1000 RPM in neutral gear. If condition is not corrected by increasing engine speed, replace fan drive unit with unit that is known to be operating properly and test by operating vehicle under same conditions. Replace unit assembly if trouble is corrected with test unit. All units are non-adjustable. Replace unit if damaged or operating improperly.
This unit is fixed blade assembly designed to flex blades as engine RPM increases. As RPM increases, blade pitch decreases, saving power and decreasing noise level. No adjustment or test is required beyond keeping fan belt adjusted to proper tension and ensuring that unit is not damaged.
Flex-Blade Fan. Scheme 7
Note. Blades should flex as engine RPM increases.
On 2.2L engines, fan control is accomplished by an or-board computer. Coolant temperature is sensed by the coolant temperature sensor located on thermostat housing. This sensor has 2 thermistor sensors, one of which is for the electric cooling fan.
The computer control cooling fan so that fan will not run during engine cranking. Fan will run continuously while A/C compressor clutch is engaged.
On non-A/C vehicles or with the A/C off, cooling fan will run at vehicle speeds above 40 MPS only if coolant temperature is above 230°F (110°C). Fan will turn off when coolant temperature drops below 220°F (104°C). At speeds below 40 MPH, the fan will switch on at 21°F (99°C) and switch off at 200°F (93°C).
On 2.6L engines, cooling fan switch is mounted in lower radiator tank and electrically isolated from the radiator. The switch is normally open and will close when coolant temperature reaches 200°F (93°C). Cooling fan relay is located on left inner fender panel. ' Fan will not operate while ignition is turned off, except California and/or High Altitude vehicles. These vehicles have a 10 minute after-run feature when radiator air discharge temperature is above 100°F (38°C).
Typical Electric Cooling Fan Chrysler Corp. Shown. Scheme 8
COOLING FAN SWITCH
On 2.6L models, if cooling fan turns on when coolant temperature reaches 200°F (93°C) and off when coolant temperature drops to 170°F 73°C), switch is operating normally.
Install jumper wire in female connector. This simulates a closed fan switch at any temperature. If fan does not cooperate with ignition switch in the "ON" position, check cooling fan, fuses and wiring.
COOLING FAN SWITCH CALIBRATION
On 2.6L models, to check switch calibration, remove switch from radiator. Immerse switch into a circulation oil bath heated to 212°F (100°C) Using a continuity light, determine if switch is closed. Switch should be closed. Lower temperature to 170°F (73°C) and determine if switch opens. Replace switch if defective.
Note. When immersing switch in oil bath, DO NOT immerse electrical terminals.
COOLING FAN MOTOR
If fan motor is not operating properly, disconnect fan motor wiring connector. Install jumper wire between fan motor and 12-volt battery. If fan runs, motor is okay. Test relays, switches, fuses and wiring.
See also:
• COOLANT SPECIFICATIONS