The engine cooling system is liquid (with forced circulation), sealed, with an expansion tank
The system is filled with an ethylene glycol-based liquid (antifreeze) that does not freeze at ambient temperatures up to -40 ° C
It is not recommended to fill the cooling system with water, as antifreeze contains anti-corrosion, anti-foaming and anti-scale additives
The engine cooling system is shown in Figure 1
In addition to the elements shown in the figure, the system includes a cast engine cooling jacket surrounding the cylinder walls in the block, combustion chambers and gas channels in the block head, and a passenger compartment heater radiator.
The circulation of fluid in the system is created by a water pump
From the pump, liquid is supplied to the engine cooling jacket, washes the combustion chamber cylinders and then enters the thermostat.
Depending on the position of the thermostat valve, fluid flows either to the water pump (at low temperature) or to the radiator (at high temperature).
The normal thermal regime of the engine is determined by the temperature of the coolant, which is automatically maintained by a thermostat in the range of 90-100 ‘C.
Radiator with a horizontal arrangement of tubes, with a tubular-ribbon aluminum core and plastic tanks
In the central part of the tank 8 there is a drain cock 10
In the tanks there are inlet 11 and outlet 1 hose pipes to the engine water jacket, pipe 4 of the steam outlet hose, pipe 2 of the return hose and fitting 9 of the automatic transmission fluid cooling hose.
There are two valves installed in the radiator cap of the engine cooling system: inlet and outlet
The exhaust valve plays a big role in ensuring optimal engine temperature.
It maintains an excess pressure of at least 0.127 MPa (1.27 kgf / cm2) in the system, increasing the temperature at which the coolant begins to boil and preventing intense vaporization
Unfortunately, if the valve is stuck in the closed position, overheating causes a significant excess of excess pressure - more than 0.15 MPa (1.5 kgf / cm2), which can lead to a rupture of the radiator or failure of one from hoses.
In turn, the jamming of the valve in the open position leads to premature boiling of the coolant.
Rinse the radiator cap once a year with running water. If in doubt, replace the plug
If you remove the plug on an overheated engine and this action coincides with a thermal shock in time, then boiling of the liquid and the formation of air pockets in the cooling system will be guaranteed.
Once a year, blow out the radiator cells with a jet of compressed air (for example, from a compressor), directing the jet first towards the oncoming air flow, and then in its direction to remove dirt, insects and road debris from the surface of the radiator. This way you can partially restore the efficiency of the radiator.
Expansion tank serves to compensate for the changing volume of the coolant depending on its temperature. The tank is made of translucent plastic
To control the coolant level, the walls are labeled "FULL" (the maximum amount of coolant) and "LOW" (the minimum amount of coolant). From above, the expansion tank is closed with a plastic stopper.
Water pump centrifugal type provides forced circulation of liquid in the cooling system
It is located on the front surface of the cylinder block and is driven by a V-ribbed belt from the crankshaft pulley
The pump has sealed bearings, no need in the replenishment of lubricants. The pump cannot be repaired, therefore, in case of failure (liquid leakage or bearing damage), it is replaced as an assembly.
Thermostat maintains the coolant at normal operating temperature and reduces engine warm-up time
The thermostat is installed in a housing fixed to the cylinder head
When the coolant temperature is below 75 ° C, the thermostat is completely closed and the liquid circulates through a small circuit, bypassing the radiator, which accelerates engine warm-up
At a temperature of about 80-84º C, the thermostat begins to open, and at 97 ° C it opens completely, circulating fluid through the radiator.
At the Mazda 6 car, two electric fans (main and additional) with plastic impellers (five- and seven-blade, respectively) are installed in the basic configuration, which provide air purge of the radiator at low vehicle speeds, mainly in urban areas or on mountain roads, when oncoming there is not enough airflow to cool the radiator.
To increase efficiency, the fans are installed in a plastic casing and attached to it at three points each
The casing, in turn, is attached at four points to the radiator (on top with two bolts, and on the bottom with stops inserted into the grooves of the brackets on the radiator supply tank)
The engine control unit controls the electric fans. Depending on the intensity of the thermal regime and the algorithm of the air conditioner, the electric fans can rotate at low and high speed
To change the speed of electric fans, the engine control unit changes their connection schemes from serial to parallel
Possible malfunctions of the cooling system and solutions
- low coolant level in expansion tank
- the thermostat is faulty
- the core of the radiator is clogged
Wash the outside of the radiator core
- the radiator tubes, hoses and engine cooling jacket are clogged with scale or sludge
Flush the cooling system and fill with fresh coolant
- one or both electric fans do not turn on
Check and repair electrical circuits. Replace sensors, relay or fan assembly if necessary
- valve damage in the radiator cap
Replace the radiator cap
The engine does not warm up to operating temperature for a long time, the thermal regime is unstable while driving:
- the thermostat is faulty
Engine overheating, cold air coming out of heater
- an excessive decrease in the coolant level due to a leak or damage to the cylinder head gasket, which causes the formation of vapor locks in the engine water jacket
Repair the coolant leak. Replace damaged cylinder head gasket
Continuous drop in coolant level in expansion tank
- leaky radiator
- coolant leaks through pipe and hose connections
Tighten the hose clamps
- damaged water pump seal
Replace water pump
- the sealing ring of the water pump housing is damaged
- the cylinder head bolts are poorly tightened (while the engine is parked on a cold engine, coolant leaks through the joint between the block head and the cylinder block; in addition, coolant may appear in the engine oil)
Tighten the cylinder head bolts to the correct torque or replace the cylinder head gasket
- the heater radiator is leaking
Replace heater core
Checking the hoses and connections of the cooling system
Open the hood and inspect the engine compartment
Find where the steam is coming from
When inspecting the engine, pay attention to the presence of coolantawns in the expansion tank
We pay attention to the integrity of the rubber hoses of the radiator, thermostat, water distribution pipes
Inspecting the connections to the outlet hose radiator
Inspecting the connection of the inlet hose
Inspecting the connection of the cooling system hoses with the pipes of the heater radiator and thermostat
Inspecting the connection of the inlet hose of the connecting tee of the engine cooling system
Inspecting the hose connections to the oil cooler
Inspecting the connection of the upper and lower heating hoses of the throttle assembly
Checking the connection of the steam outlet hose to the radiator and expansion tank