DESCRIPTION
The basic liquid cooling system consists of a radiator, water pump, thermostat, cooling fan, pressure cap, heater (if equipped), various connecting hoses and cooling passages in the block and cylinder head. Many cars use a fan clutch (incorporating a thermostatic control) or flexible fan blade. These reduce noise and power requirements at higher engine speeds. In addition, some cars use a thermostatically controlled electronic fan which is actuated by thermal relay switches.
Some models may use a thermostatic vacuum switch to advance ignition timing in the event of overheating. Most models use a coolant recovery system to prevent loss of coolant.
Draining
Remove radiator cap and open heater control valve to maximum heat position. Open drain cocks or remove plugs in bottom of radiator and engine block. In-line engines usually have one plug or drain cock, while "V" type engines will have 2; one in each bank of cylinders.
Cleaning
A good cleaning compound will remove most rust and scale. Follow manufacturer's instructions in the use of cleaner. If considerable rust and scale has to be removed, flushing should be used. Clean radiator air passages by blowing with compressed air from back to front.
Flushing
| CAUTION | Some manufacturers may use an aluminum/plastic radiator on some models (identified by a note below the filler neck). According to manufacturer's recommendations, material used for cleaning and flushing must be compatible with aluminum. |
- Back flushing is a very effective means of removing rust and scale from a cooling system. For best results the radiator, engine and heater core should be flushed separately.
- To flush radiator, connect flushing gun to water outlet of radiator and disconnect water inlet hose. To prevent flooding engine, use a leadaway hose connected to radiator inlet. Use air in short bursts only; this will prevent damage to radiator. Continue flushing until water runs clear.
- To flush engine, first remove thermostat and replace 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 set 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.
Scheme 1
- Visually inspect thermostat for corrosion and proper sealing of valve and seat. If satisfactory, suspend thermostat and a thermometer in a container with a 50/50 mixture of anti-freeze and water. (Scheme 1)
- Do not allow either thermostat or thermometer to touch bottom of container as this concentration of heat could cause an incorrect reading. Heat water until thermostat just begins to open.
- Read temperature on thermometer. This is the initial opening temperature and should be within specifications. Continue heating water until thermostat is fully open and note temperature. This is the fully opened temperature. If either reading is outside of specifications, replace thermostat, as it is not adjustable. (Scheme 1): Testing Thermostat in Anti-Freeze/Water Solution NOTE: Support thermometer so it does not touch bottom of container. NOTE: Chevrolet recommends hanging thermostat in 33% glycol solution at 25°F (4°C) above temperature stamped on thermostat. Valve should open. Remove thermostat from solution and place in similar solution at 10°F (-12°C) below stamped temperature. Valve should close.
Pressure Testing
A cooling system pressure tester is used to test both radiator cap and complete cooling system. Test as follows, following tool manufacturer's instructions.
Radiator Cap
Visually inspect radiator cap, then dip cap in water and connect to tester. Pump tester to bring pressure to upper limit of cap specifications. If cap fails to hold pressure within specifications, replace cap.
Testing Radiator Pressure Cap. Scheme 2
Note. Wet cap gasket before testing.
Scheme 3
- With engine off, wipe radiator filler neck seat clean. Fill radiator to correct level. Attach tester to radiator and pump until pressure is at upper limit of radiator rating.
- If pressure drops, inspect for external leaks. If no leaks are apparent, detach tester and run engine until normal operating temperature is obtained. Reattach tester and observe. If pressure builds up immediately, a possible leak exists from a faulty head gasket or crack in head or block.
- If there is no immediate pressure build up, pump tester to within system pressure range (on radiator cap). Vibration of gauge pointer indicates compression or combustion leak into cooling system. Isolate leak by shorting each spark plug wire to cylinder block. Gauge pointer should stop or decrease vibration when leaking cylinder is shorted. CAUTION: Pressure may build up quickly. Release any excess pressure or cooling system damage may result.
- Remove engine and transmission (automatic only) oil dipsticks and check if water drops appear in oil. If so, a serious internal leak is indicated. If all checks are negative and system holds pressure for 2 minutes, there are no serious leaks in system. CAUTION: Do not disconnect spark plug wires while engine is operating, or operate engine with spark plug shorted for more than one minute, as catalytic converter may be damaged. (Scheme 3): Pressure Testing Cooling System
Anti-Freeze Concentration
Test anti-freeze concentration using anti-freeze tester. Tester should have a temperature-compensating feature, as failing to take temperature into consideration could cause an error as large as 30°F (-1°C). Follow manufacturer's instructions for correct use of tester.
A coolant recovery system differs from other cooling systems in that an overflow bottle is connected to the radiator overflow hose. The overflow bottle is transparent or translucent to permit checking of coolant level without removing radiator cap. The only adjustment or test required is to keep vent hole or hose clean and to check 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 the system. Vacuum draws coolant, stored in overflow bottle, back into radiator. In a properly maintained cooling system, the only coolant loss will be through evaporation.
Typical Coolant Recovery System. Scheme 4
General Motors FWD Models, Camaro, Corvette, Fiero & Firebird
All electrically-driven fans are actuated by thermal relay switches. Thermal switches turn fan motor on and off when necessary. Air conditioned vehicles are equipped with over-ride switches. These switches turn fan motor on whenever air conditioning system is operating, and return fan motor control to thermal relay when system is turned off.
Thermostatically Controlled Electric Fan. Scheme 5
Coolant temperature switch turns fan motor on at specified temperatures. See COOLING FAN TEMPERATURE SWITCH SPECIFICATIONS table.
Fan will also come on instantly when A/C is turned on. Fan motor shuts off when ignition switch is turned off, regardless of coolant temperature. (Scheme 8)- (Scheme 15).
| Application | Temperature °F (°C) | |
|---|---|---|
| "A" Bodies | ||
| Celebrity, Century, Ciera, & 6000 | 228 (110) | |
| "F" Bodies | ||
| Camaro & Firebird | 238 (122) | |
| "J" Bodies | ||
| Cavalier, Cimarron, Firenza, Skyhawk, & Sunbird | 238 (122) | |
| "L" Bodies | ||
| Beretta & Corsica | (1) | |
| "P" Body | ||
| Fiero | 235 (120) | |
| "N" Bodies | ||
| Calais, Grand Am, Skylark, & Somerset | 230 (117) | |
| "Y" Body | ||
| Corvette | 238 (122) | |
| (1) Information not available. | ||
| (1) | Information not available. |
COOLING FAN TEMPERATURE SWITCH SPECIFICATIONS
TESTING
Disconnect fan motor wire connector and connect it with 14-gauge wire to a good 12-volt battery. If fan runs, motor is okay, indicating car battery, coolant relay, coolant temperature switch, or A/C relay may be defective. If fan motor does not run when connected directly to a good battery, replace fan motor.
This unit is a flexible blade assembly designed to flex blades as engine RPM increases. As RPM increases, blade pitch decreases, thereby saving power and decreasing noise level. Keep fan belt adjusted to proper tension as necessary. (Scheme 6)
Flex Blade Fan Assembly. Scheme 6
All General Motors
Most air conditioned models use a thermostatically controlled fluid fan and torque control clutch. Thermal control drive is a silicone-filled coupling connecting fan to a fan pulley, and is operated by a control valve. The Control valve is operated by a temperature sensitive bi-metallic coil (or strip) and controls flow of silicone through the clutch.
During periods of operation when radiator discharge air temperature is low, fan clutch speeds are slowed, decreasing load on fan belt. High radiator discharge air temperature causes bi-metallic coil or strip to allow a greater flow of silicone to enter clutch. This increases drag between driven member and driving member resulting in a higher fan speed and increased cooling.
Thermostatically Controlled Fan Assembly. Scheme 7
Note. Shown with stamped face and bi-metal coil spring.
- In cases of engine overheating or insufficient air conditioning start with a cool engine to ensure complete fan clutch disengagement. Cover radiator grille sufficiently to induce high engine temperature.
- Start engine and operate at 2000 RPM. Turn on air conditioning (if equipped). A fan roar will be noticed when fan clutch engages. NOTE: It takes approximately 5-10 minutes for temperature to become hot enough to allow engagement of fan clutch. While operating engine under this condition, observe temperature light or gauge to prevent overheating. If car overheats, remove cover from radiator grille.
- When clutch engages, remove radiator grille cover and turn A/C off to assist in engine cooling. After several minutes fan clutch should disengage. This can be determined by a reduction in fan speed and roar. If fan fails to function as described, it should be replaced.
WIRING DIAGRAMS
Note. Wiring diagram information available for following General Motors vehicles only.
