1.1 3.6L gasoline engine cooling circuit (on the example of models with an additional heater)
1 Expansion tank
2 Non-return valve, in the coolant hose, not visible from the outside
3 Coolant cut-off valve N279 for the heater
4 Heater radiator, when replacing, replace the coolant
5 Coolant pipe, installed transversely at the rear
6 Oil cooler
7 Non-return valve
8 Additional heatsink
9 Upper coolant hose
10 Lower coolant hose
11 Radiator
12 Coolant pipe, installed transversely at the front
13 Coolant circulation pump "V55"
14 Oil cooler
15 Coolant pipe, with thermostat housing
16 Thermostat
17 Additional heater
18 Coolant pump
19 Cylinder block
20 Cylinder head
21 Choke, in coolant hose, not visible from outside
22 Coolant pipe, rear
1.2 1.4L petrol engine cooling circuit
Light contour Coolant lines of the engine cooling system
Dark outline Intercooler coolant lines
1 Expansion tank
2 Coolant circulation pump "V50"
3 Intercooler, in intake manifold
4 Non-return valve, in the coolant hose, not visible from the outside
5 Heater radiator
6 Thermostat housing
7 Choke, in coolant hose, not visible from outside
8 Oil cooler
9 Radiator
10 Additional radiator for intercooler
11 Turbocharger
12 Head and cylinder block
13 Additional heater, if equipped
14 Coolant pump
1.3 Cooling circuit for 1.8 and 2.0 l petrol engines (on the example of models with DSG)
1 Radiator
2 Coolant circulation pump "V51"
3 Coolant pump
4 Thermostat
5 Oil cooler
6 Head and cylinder block
7 Turbocharger
8 Expansion tank
9 To additional heater
10 From auxiliary heater
11 Heater radiator
12 DSG fluid cooler
13 Connection of coolant lines
14 Radiator control valve 12
1.4 2.0L diesel engine cooling circuit (CFFB, CFGB and CLJA)
1 Expansion tank
2 EGR radiator, replace coolant after replacement
3 To auxiliary heater
4 From auxiliary heater
5 Cylinder block, replace coolant after replacement
6 Heater radiator, replace coolant after replacement
7 Choke, in coolant hose, not visible from outside
8 DSG fluid cooler
9 Radiator regulator 8
10 Oil cooler, replace coolant after replacement
11 Coolant circulation pump no. 2 "V178"
12 Radiator, after replacement, replace the coolant
13 Sensor "G83" coolant temperature at the radiator outlet
14 4/2 way valve, with thermostat
15 Coolant pump
16 Cylinder head, replace coolant after replacement
The engine cooling system works according to the following algorithm. Until the engine is warm, the coolant (coolant) is pumped by a water pump only in the head and cylinder block, as well as in the interior heater heat exchanger. Thus, the engine warms up quickly. When the coolant temperature rises to a certain value (controlled by ECT sensor) the thermostat opens a large cooling circuit and the coolant circulates additionally through the radiator, being cooled by the air passing through it. This maintains the operating temperature of the engine. When the coolant temperature reaches an even higher value, the cooling system fan turns on, which begins to create additional air flow through the radiator fins to more intensively remove heat from it.
In addition to the heater radiator, an oil cooler can be included in the cooling system circuit (see chapter 2), auxiliary heater radiator (in the presence of, see Part B), DSG Fluid Radiator (on models with DSG, see chapter 7), radiator for intercooler (on 1.4L petrol models, see Chapter 4) and EGR cooler (on diesel models see chapter 4).
The coolant pump, or water pump, is driven by:
- on petrol models 1.4 and 3.6 l - with a belt for driving auxiliary units;
- on gasoline models 1.8 and 2.0 l - with a separate toothed belt from the balancing shaft;
- on diesel engines - from the crankshaft through the timing belt.
Electric coolant circulation pump "V50" or "V51" is responsible for coolant circulation when additional functions are activated, for example: using residual heat to warm up the passenger compartment and pumping coolant after turning off the engine.
The residual heat function allows the vehicle interior to be kept at the desired temperature when the engine is switched off, as long as the coolant temperature remains high enough. To do this, the circulation pump, on commands from the engine control unit, maintains the flow in the cooling system circuit. If there is not enough residual heat, the climate control unit disables the residual heat function. Coolant pumping after turning off the engine is a protective function of the engine. In this way, vaporization is prevented in the areas of the cylinder head after the engine is turned off. The function is activated if the coolant temperature exceeds 105°C after the engine is switched off and the vehicle has been driven with a correspondingly high load in the previous driving cycle.
Precautionary measures
Before working in the engine compartment, especially in the radiator fan area, be sure to disconnect the negative cable from the battery and the fan wiring connector, because. it may turn on due to the effect of heat conduction even when the ignition is off.
Do not open the cap of the coolant expansion tank until the engine has completely cooled down to avoid burns from hot liquid or its vapor.
If necessary, open the cap of the expansion tank when the engine is hot, wrap it with rags. Turn the lid off slowly, gradually reducing the steam pressure.