Engine Cooling System & Automatic Transmission Cooling System: Overview Dodge Caravan IV

DESCRIPTION - COOLING SYSTEM

The cooling system components consist of a radiator, electric fan motors, shroud, pressure cap, thermostat, transmission oil cooler, water pump, hoses, clamps, coolant, and a coolant reserve system to complete the circuit.

DESCRIPTION - HOSE CLAMPS

The cooling system uses spring type hose clamps. If a spring type clamp replacement is necessary, replace with the original Mopar(R) equipment spring type clamp.

Scheme 9

OPERATION - COOLING SYSTEM

The engine cooling systems primary purpose is to maintain engine temperature in a range that will provide satisfactory engine performance and emission levels under all expected driving conditions. It also provides hot water (coolant) for heater performance and cooling for automatic transmission oil. It does this by transferring heat from engine metal to coolant, moving this heated coolant to the radiator, and then transferring this heat to the ambient air.

1. When engine is cold: thermostat is closed, cooling system has no flow through the radiator. The coolant bypass flows through the engine only.
2. When engine is warm: thermostat is open, cooling system has bypass flow and coolant flow through radiator.

Coolant flow circuits for the 2.4L and 3.3/3.8L engines are (Scheme 10)

Scheme 10

OPERATION - HOSE CLAMPS

The spring type hose clamp applies constant tension on a hose connection. To remove a spring type hose clamp, use Special Tool 6094 or equivalent, constant tension clamp pliers to compress the hose clamp. (Scheme 11)

Scheme 11

DESCRIPTION - ENGINE COOLANT

The cooling system is designed around the coolant. The coolant must accept heat from engine metal, in the cylinder head area near the exhaust valves and engine block. Then coolant carries the heat to the radiator where the tube/fin radiator can transfer the heat to the air.

The use of aluminum cylinder blocks, cylinder heads, and water pumps requires special corrosion protection. Mopar(R) Antifreeze/Coolant, 5 Year/100,000 Mile Formula (MS-9769), or the equivalent ethylene glycol base coolant with hybrid organic corrosion inhibitors (called HOAT, for Hybrid Organic Additive Technology) is recommended. This coolant offers the best engine cooling without corrosion when mixed with 50% Ethylene Glycol and 50% distilled water to obtain a freeze point of -37°C (-35°F). If it loses color or becomes contaminated, drain, flush, and replace with fresh properly mixed coolant solution.

The green coolant MUST NOT BE MIXED with the orange or magenta coolants. When replacing coolant the complete system flush must be performed before using the replacement coolant.

DESCRIPTION

The coolant recovery/reserve system container is mounted in the engine compartment. see scheme 27 The container is made of plastic.

OPERATION

The coolant recovery system works with the radiator pressure cap to use thermal expansion and contraction of the coolant to keep the coolant free of trapped air. Provides a convenient and safe method for checking coolant level and adjusting level at atmospheric pressure without removing the radiator pressure cap. It also provides reserve coolant to cover deaeration, evaporation, or boiling losses.

The engine block heater is available as an optional accessory on all models. The heater is operated by ordinary house current (110 Volt A.C.) through a power cord located behind the radiator grille. This provides easier engine starting and faster warm-up when vehicle is operated in areas having extremely low temperatures. The heater is mounted in a core hole (in place of a core hole plug) in the engine block, with the heating element immersed in coolant.

The block heater element is submerged in the cooling system's coolant. When electrical power (110 volt A.C.) is applied to the element, it creates heat. This heat is transferred to the engine coolant. This provides easier engine starting and faster warm-up when vehicle is operated in areas having extremely low temperatures.

The engine coolant temperature sensor threads into the top of the thermostat housing. see scheme 28 New sensors have sealant applied to the threads.

The engine coolant temperature sensor threads into a coolant passage on lower intake manifold near the thermostat. see scheme 31 New sensors have sealant applied to the threads.

The engine cooling thermostats are a wax pellet driven, reverse poppet choke type. The thermostat is mounted in a housing on the coolant outlet of the engine. see scheme 33and see scheme 35.

The engine cooling thermostat is a wax pellet driven, reverse poppet choke type. The thermostat is designed to provide the fastest warm up possible by preventing leakage through it and to guarantee a minimum engine operating temperature of 88 to 93°C (192 to 199°F). The thermostat also will automatically reach wide open so it will not restrict flow to the radiator as temperature of the coolant rises in hot weather to around 104°C (220°F). Above this temperature the coolant temperature is controlled by the radiator, fan, and ambient temperature, not the thermostat.

The thermostat is operated by a wax filled container (pellet) which is sealed. When heated coolant reaches a predetermined temperature, the wax expands enough to overcome the closing spring and water pump pressure, which forces the valve to open.

The cooling system pressure cap is located on the radiator. The cap construction includes; stainless steel swivel top, rubber seals, and retainer, main spring, and a spring loaded valve. (Scheme 12)

Scheme 12

The cooling system is equipped with a pressure cap that releases excessive pressure; maintaining a range of 97-124 kPa (14-18 psi).

The cooling system will operate at higher than atmospheric pressure. The higher pressure raises the coolant boiling point thus, allowing increased radiator cooling capacity.

There is also a vent valve in the center of the cap. This valve also opens when coolant is cooling and contracting, allowing the coolant to return to cooling system from coolant reserve system tank by vacuum through a connecting hose. If valve is stuck shut, or the coolant recovery hose is pinched, the radiator hoses will be collapsed on cool down. Clean the vent valve and inspect coolant recovery hose routing, to ensure proper sealing when boiling point is reached. (Scheme 12)

The gasket in the cap seals the filler neck, so that vacuum can be maintained, allowing coolant to be drawn back into the radiator from the reserve tank. If the gasket is dirty or damaged, a vacuum may not be achieved, resulting is loss of coolant and eventual overheating due to low coolant level in radiator and engine.

The dual radiator fans are mounted to the back side of the radiator. see scheme 45 The radiator fan consist of the fan blade, electric motor and a support shroud which are all serviced as an assembly.

RADIATOR FAN OPERATION CHART

The radiator fan relay is a solid state type and is located on the front bumper reinforcement. see scheme 46 Refer to appropriate SYSTEM WIRING DIAGRAMS article for a circuit schematic.

The solid state radiator fan relay is controlled by the Powertrain Control Module (PCM) by way of a Pulse Width Modulated (PWM) signal. The relay control circuit supplies a 12 volt signal to the PCM. The PCM then pulses the ground circuit to achieve fan on time. The relay provides a voltage to the fan motors which is proportional to the pulse width it receives from the PCM. The duty cycle ranges from 30% for low speed operation, then ramps-up to 100% for high speed operation. This fan control system provides infinitely variable fan speeds, allowing for improved fan noise, A/C performance, better engine cooling, and additional vehicle power.

To control operation of the relay, the PCM looks at inputs from

1. Engine coolant temperature
2. A/C pressure transducer
3. Ambient temperature from the body controller
4. Vehicle speed
5. Transmission oil temperature

The PCM uses these inputs to determine when the fan should operate and at what speed. For further information on fan operation, (Refer to COOLING/ENGINE/RADIATOR FAN - OPERATION) .

The water pump has a cast aluminum body and housing with a stamped steel impeller. The water pump bolts directly to the block. (Scheme 13) The cylinder block to water pump seal is provided by a rubber O-ring. The water pump is driven by the engine timing belt.

Scheme 13

Scheme 14

1. Disconnect negative cable from battery.
2. Raise vehicle on a hoist.
3. Remove the right inner splash shield.
4. Remove the accessory drive belts «(Refer to COOLING/ACCESSORY DRIVE/DRIVE BELTS - REMOVAL)»(ref-248908-S35636680612007022700000).
5. Drain the cooling system «(Refer to COOLING - STANDARD PROCEDURE)»(ref-248908-S09724997062007022700000).
6. Support engine from the bottom and remove right engine mount. «(Refer to ENGINE/ENGINE MOUNTING/RIGHT MOUNT - REMOVAL)»(ref-248909-S38441119202007022700000).
7. Remove right engine mount bracket. (Scheme 14)
8. Remove the timing belt «(Refer to ENGINE/VALVE TIMING/TIMING BELT AND SPROCKET(S) - REMOVAL»(ref-248909-S37184467492007022700000) ).
9. Remove timing belt idler pulley.
10. Hold camshaft sprocket with Special tool C-4687 and adaptor C-4687-1 while removing bolt. Remove both cam sprockets.
11. Remove the timing belt rear cover «(Refer to ENGINE/VALVE TIMING/TIMING BELT COVER(S))»(ref-248909-S15417656572007022700000).
12. Remove the generator and bracket. (Scheme 14) 1 - BRACKET - ENGINE MOUNT 5 - BOLT 2 - BOLT 6 - TENSIONER - DRIVE BELT 3 - GENERATOR 7 - BOLT 4 - BOLT 8 - BOLT
13. Remove water pump to engine attaching screws. see scheme 49

The water pump has a die-cast aluminum body and a plastic impeller. It bolts directly to the timing chain case cover, using a rubber seal for sealing. (Scheme 15) It is driven by the accessory drive belt.

Scheme 15

Scheme 16

1. Drain the cooling system. «(Refer to COOLING - STANDARD PROCEDURE)»(ref-248908-S09724997062007022700000)
2. Remove the accessory drive belt shield.
3. Remove the accessory drive belt. «(Refer to COOLING/ACCESSORY DRIVE/DRIVE BELTS - REMOVAL)»(ref-248908-S35636680612007022700000)
4. Remove water pump pulley bolts. (Scheme 15) NOTE: To remove the water pump pulley, it MUST first be positioned between water pump housing and drive hub. The pulley can then be removed with the water pump assembly.
5. Rotate pulley until openings in pulley align with water pump drive hub spokes. (Scheme 16) Move pulley inward between pump housing and hub. (Scheme 16) 1 - HUB - WATER PUMP 2 - PULLEY - WATER PUMP
6. Position pulley to allow access to water pump mounting bolts. Remove water pump mounting bolts. (Scheme 17)
7. Remove water pump with the pulley loosely positioned between hub and the pump body.
8. Remove and discard the seal.
9. Clean seal groove and sealing surfaces on pump and timing chain case cover. Take care not to scratch or gouge sealing surfaces.

Scheme 17

The 2.4L engine uses a metal tube to connect the engine block to the lower radiator hose and heater return. (Scheme 18) The tube has an O-ring for block to tube sealing and bolts attach the tube to the engine block.

Scheme 18

The automatic transmission cooler is located in the front of the radiator and behind the front fascia and is combined with the A/C condenser. The transmission cooler is a heat exchanger that allows heat in the transmission fluid to be transferred to the air passing over the cooler fins.

The Transmission oil cooler/A/C condenser assembly is equipped with quick connect fitting for the transmission oil cooler lines, a tapping block, for the receiver/drier, and mounting provisions for the power steering cooler.

The transmission oil cooler/AC condenser is serviced as an assembly. For removal on vehicles equipped with 2.4L/3.3L/3.8L engines, refer to 2.4L/3.3L/3.8L ENGINES , vehicles equipped with 2.5L/2.8L engines, refer to 2.5L/2.8L ENGINES . For installation on vehicles equipped with 2.4L/3.3L/3.8L engines, refer to 2.4L/3.3L/3.8L ENGINES , and vehicles equipped with 2.5L/2.8L engines, refer to 2.5L/2.8L DIESEL ENGINES .