Woodstock Auto Repair

Toll free:(519) 421-2313
Mon - Fri: 8:00 AM - 5:00 PM

Car Care Cooling System

  1. Antifreeze / Coolant
  2. Cooling Fan
  3. Pressure Cap
  4. Reservoir
  5. Heater Core
  6. Heater Control Valve
  7. HVAC Hoses
  8. Engine Heater
  9. HVAC
  10. Thermostat

Antifreeze / Coolant

Description: The most common formulation of antifreeze is green in color and uses ethylene glycol as a base with anti-corrosion additives mixed in. The ethylene glycol part of the formula provides crucial anti-freezing characteristics and the additives deliver the anti-rust and anti-corrosion capabilities. Beginning with 1995 models, most GM vehicles started coming from the factory filled with an extended-life antifreeze, trademarked as DEX-COOL®. Distinctively different in appearance, DEX-COOL®, and its aftermarket equivalents, is an orange/amber color. It still uses ethylene glycol as a base, but contains a different additive package than standard green-coloured antifreeze. This coolant is designed to protect cooling systems for up to 225,000 kilometres or five years. Other antifreeze formulations include silicate-free for Japanese cars and phosphate-free for European cars.

Purpose: When properly mixed, antifreeze and water provide excellent anti-freeze, anti-boil and anticorrosive properties.

Maintenance Tips/Suggestions: Check your owner's manual for antifreeze usage specifications. Antifreeze, when mixed at a 50/50 ratio with water, provides excellent anti-freeze, anti-boil, and anti-corrosive properties. In extremely cold environments, the ratio for standard ethylene glycol can go as high as 70% antifreeze, 30% water. With DEX-COOL®, the maximum ratio of antifreeze to water is 60/40. Although DEX-COOL® type antifreeze can be mixed with standard ethylene glycol antifreeze, DEX-COOL® loses its 5 yr./225,000 life. As such, it's best not to mix antifreeze types unless absolutely necessary.

All coolants must be diluted with water at the proper ratios and should not be used full-strength. Full-strength antifreeze actually has a lower freeze point than when mixed with water. Generally, standard ethylene glycol type antifreeze should be changed every two years or 40,000 kilometres. Even though the coolant freeze protection may test OK with a hydrometer (freeze protection only drops with extreme dilution, not with age), the additives break down over time.

When changing coolant, it also presents an opportune time to replace bad cooling system hoses. Leaking, brittle, spongy, cracked, or rotted hoses should be replaced before new antifreeze is installed. Hose clamp connections should also be checked to ensure that they're secure and free from leaks. If you decide to service your cooling system yourself, use extreme caution: Opening a hot radiator or coolant reservoir/overflow tank can cause severe burns. Be sure that both the engine and cooling system are cool before you begin any heating/cooling system maintenance or repairs. Because of lower hood profiles and cramped engine quarters, it's also possible that your car may be equipped with an air bleed for the cooling system. Unless the cooling system is bled properly, air may stay trapped in the system and cause erratic temperatures, or in extreme cases, engine or cooling system damage. If you're unsure about any aspect of cooling system service, don't take a chance. Have your car looked at by one of our professional service technicians.

Cooling Fan

Description: Two different types of cooling fans may be used for the cooling system. Traditionally, cars have used belt-driven, mechanical fans using the engine to turn them. Mechanical fans are still used on some cars and light trucks. These fans now use a temperature-sensitive fan clutch that allows the fan to disengage and engage according to different operating conditions. Electric cooling fans began to emerge around 1980 and only come on when needed. The evolution from mechanical fans to electric fans arose from sideways-mounted (transverse) engines and transmissions, and the need to reduce weight while increasing fuel economy. Some vehicles may use multiple electric fans for better control of the cooling system. Today's cars use electric cooling fans controlled by the same computer that controls the engine.

Purpose: The cooling fan circulates air through the radiator so it can release engine heat into the surrounding air. With the introduction of fan clutches and electric cooling fans, fans have become more efficient by operating only when they need to. Electric cooling fans also improve the operation of the air conditioning system. When traveling down the road, usually at roads speeds above 30 mph, mechanical fans basically freewheel and electric fans stay off. Air passing through the radiator because of vehicle movement is all that's needed to ensure heat exchange.

Maintenance Tips/Suggestions: A fan that does not provide sufficient circulation usually causes overheating and poor air conditioning operation. A fan that stays engaged at all times can cause poor fuel economy, unwanted noise and may run the battery dead (electric fans with A/C off). First, inspect the area around the radiator to make sure it's free of leaves and other debris. On cars with mechanical fans, turn the engine off and check to make sure the fan is intact and that the drive belt is tight. On cars with electric fans, check your owner's manual to determine what fuses and relays may be involved in controlling the fan. Replace any bad fuses and make sure that the cooling fan relay is properly seated in its socket. Beyond that, if you suspect a problem with your car's fan, have it inspected right away by one of our professional service technicians.

Pressure Cap

Description: The pressure cap controls pressure in the cooling system. The cap may be mounted on the radiator filler neck or on top of the coolant reservoir. That's why a pressure cap isn't always a radiator cap.

Purpose: The pressure cap controls pressure in the cooling system. The cap may be mounted on the radiator filler neck or on top of the coolant reservoir. That's why a pressure cap isn't always a radiator cap.


Maintenance Tips/Suggestions: Never remove the pressure cap from a hot engine. Doing so can cause hot coolant to spray from the cooling system, causing severe burns. The pressure cap is a critical part of the cooling system and it should be checked at least once a year. Replace the cap if bad. Any type of cooling system maintenance should include a check of the pressure cap. Symptoms of a faulty pressure cap may include overheating and a coolant reservoir that either doesn't show a rise in the coolant level with the engine warm, or a reservoir that doesn't show a drop in coolant level as the engine cools. Pressure caps vary with different applications, so don't assume that one cap is as good as the next. For best results, use the replacement cap specified for your vehicle.


Description: The reservoir, or expansion tank as it's sometimes called, is a semi-transparent plastic bottle that may be pressurized or non-pressurized. The reservoir usually has level markings for quick checking of the coolant level.

Purpose: The reservoir allows for expansion of the coolant when the engine is warm, rather than having the coolant spill out of an overflow tube. When connected to the radiator with a properly functioning pressure cap, the reservoir enables the radiator to be consistently full, regardless of temperature.


Maintenance Tips/Suggestions: Check the coolant level at least every oil change; weekly is even better. A reservoir that consistently drops in coolant level after topping off usually indicates a leak. The hose between the reservoir and radiator may be loose or damaged, the pressure cap may be faulty, or there may be a leak elsewhere in the cooling system. If your inspection of the system provides no clues, have the cooling system pressure tested and checked by our qualified professional.

Heater Core

Description: A small radiator-like heat exchanger mounted inside the HVAC housing. The heater core has an inlet and outlet that enables coolant flow through the core. A series of tubes and fins provide the surface area for heat exchange.

Purpose: The heater core provides a source of heat for the interior of the vehicle. The driver, using the heater controls and blower motor, controls the exact amount of heat.


Maintenance Tips/Suggestions: The heater core does not require regular maintenance by itself, but is cared for by regular maintenance of the cooling system. This includes coolant changes per the manufacturer's recommendations. Symptoms of a faulty heater core include coolant on the floor of the interior, a strange smell while the heat is turned on, and poor heater output. Have these symptoms checked out by a qualified technician, who can quickly determine where the fault lies. Problems with a heater core only tend to get worse; so don't put off having the system checked.

Heater Control Valve

Description: A heater control valve may be located in one of the heater hoses to regulate coolant flow to the heater core. The valve is usually vacuum-controlled, which is operated by controls on the dash.

Purpose: The valve is used help control heater output.


Maintenance Tips/Suggestions: Insufficient heat, or heat that can't be turned off may indicate a problem with the heater control valve. Inspect the valve to make sure that its vacuum line is properly connected. If the valve has an external linkage arm, operate the heater controls and watch to see if the valve changes position. If you have any doubts about the valve's operation, have the heating system checked by a qualified service professional.

HVAC Hoses

Description: High- and low-pressure refrigerant hoses connect the main parts of the air conditioning system together. An orifice tube or thermostatic expansion valve regulates refrigerant flow in the A/C system. Service fittings provide connections for service equipment so that system pressures can be checked and refrigerant may be recovered and recycled. Heater hoses connect the engine's cooling system to the heater core. A heater control valve may be located in one of the heater hoses to regulate coolant flow to the heater core.

Purpose: Refrigerant hoses provide a path for refrigerant and refrigerant oil between the key components of the A/C system. The orifice tube (most common) or thermostatic expansion valve ensures proper refrigerant flow for different operating conditions. Service fittings, unique for each type of refrigerant, enable the connection of service equipment and reduce the chances of mixing different types of refrigerant. Heater hoses provide a supply and return path for warm engine coolant circulating in the heater core. The heater control valve may help control heater output by opening and closing coolant flow to the heater core.


Maintenance Tips/Suggestions: Hoses and valves should be inspected periodically for condition and to make sure all connections are secure. Chafed, cut or damaged hoses should be replaced. Poor A/C cooling may indicate problems with the orifice or expansion valve. Insufficient heat, or heat that can't be turned off may indicate a problem with the heater control valve. When in doubt, have your car's HVAC system evaluated by our qualified professional.

Engine Heater

Description: Electrically operated heaters are often available as optional equipment on cars and light trucks. The heater may warm coolant with a heating element located in a coolant hose or in the engine block, or the heater may be located in a position that warms the engine oil.

Purpose: Engine heaters help to provide easier starting in extremely cold temperatures.

Maintenance Tips/Suggestions: The engine heater should be checked every fall to make sure that the heating element still works. With the engine cold and not running, plug the heater into an outlet. Wait several minutes and feel the location of the heater. It should feel warm to the touch. You may have to wait a little longer to feel the heat from an engine oil heater; it depends on the location and the heating ability of the heater's element. Replace the heater if bad


Description: Usually used with Automatic Temperature Control (ATC), there are typically three sensors that sense temperature. One sensor is located on the outside of the car to sense outside air temperature. A second sensor is located in the interior to monitor temperature inside the car. The third sensor is usually located in the HVAC ducting, to sense delivered air temperature.

Purpose: The system uses information from the sensors to make decisions on output commands to the HVAC system and the blower motor.

Maintenance Tips/Suggestions: Problems with the HVAC sensors may result in poor regulation of cooling and heating. It is also possible that the speed of the blower motor will not change speed according to system demands. Regardless of the symptom, have it diagnosed as soon as possible by a professional technician.


Description: A typical thermostat consists of an outer body that houses a temperature-sensitive valve that opens and closes based off coolant temperature. Most thermostats operate completely off coolant temperature, but some cars use computer-controlled thermostats that are controlled by the powertrain control module (PCM). Most thermostats are located towards the top of the engine, in the outlet going to the radiator. In some cases, the thermostat may be mounted towards the bottom of the engine near the inlet to the engine. Thermostats have a rating in degrees that reflects the typical cooling system temperature maintained by the thermostat.

Purpose: The thermostat is basically the cooling system's temperature regulator. When the engine is cold, the thermostat stays closed and keeps coolant flowing within the engine itself. This helps the coolant in the engine to warm quickly. The warming coolant causes the valve in the thermostat to open slightly, allowing some of the coolant to flow to the radiator and back into the engine. As the engine continues to warm, the thermostat opens more in relation to the heat of the coolant. Under normal conditions with a fully warmed engine, the thermostat will be completely open.

Maintenance Tips/Suggestions: The thermostat is a critical part of the cooling system that can cause various symptoms and problems. A bad thermostat can result in low heater output, overheating, poor fuel economy, knocking or pinging when accelerating, high idle speed, an electric cooling fan that runs continuously, and low temperature gauge readings. An important footnote: a faulty thermostat can even cause your car to fail an emissions test. To determine whether your car's thermostat is operating properly, have the cooling system checked by one of our qualified service technicians.