Cooling system, air conditioning and exhaust treatment
Operating temperature, F-gas regulations and modern after-treatment (DPF, SCR, AdBlue)
A diesel engine on a heavy machine only performs cleanly and reliably if temperature is kept in the right range and if the exhaust's aftertreatment works. At the same time there are today both environmental requirements and personnel certificates tied to cooling systems air conditioning and emissions cleaning that you as a mechanic must know.
§The cooling system's task
The cooling system removes excess heat from the engine so it neither becomes too hot nor runs too cold. A water pump circulates the coolant through the engine and radiator, a thermostat controls the flow so the engine quickly reaches operating temperature, and a fan draws air through the radiator. The coolant contains antifreeze and corrosion protection — use the mixture and interval the manufacturer prescribes.
- 01Check coolant level and condition and for leaks.
- 02Keep coolers and cooling grilles clean — in agriculture and contractor work, chaff and dust stick quickly.
- 03Check hoses, clamps, and water pump for leaks
- 04Be aware of overheating as a symptom of thermostat, pump or fan failure.
§Air conditioning and F-gas rules
Many machines have air conditioning in the cab and the system contains a refrigerant that is an F-gas (fluorine-containing greenhouse gas). The EU's F-gas regulation requires that whoever performs work on a system with F-gases — for example draining filling or repairing — must have a personal F-gas certificate. The refrigerant must not be released into the atmosphere but must be collected and handled correctly. Without the certificate you must not open the refrigerant circuit.
§Exhaust emission control on modern engines
To meet the current emission standards (the European Stage steps for non-road machinery) modern diesel engines have a chain of after-treatment. Understand the central components as they are a frequent source of fault codes and operating failures:
| Component | Function | You should know this |
|---|---|---|
| EGR (exhaust gas recirculation) | Returns part of the exhaust to the intake to lower the combustion temperature and thus NOx | Can build up with soot; causes power loss and error codes |
| DOC (oxidation catalyst) | Oxidises carbon monoxide and unburned fuel | Helps to warm the exhaust for regeneration |
| DPF (diesel particulate filter) | Fanger sodpartikler fra udstødningen | Must be regenerated (burned); a blocked DPF causes power loss |
| SCR + AdBlue | Injects AdBlue (aqueous urea solution), which with the catalyst converts NOx to nitrogen and water | Low or incorrect AdBlue, or defective dosing, puts the engine into limp mode |
§Regeneration and AdBlue
The particle filter collects soot and must be regenerated at regular intervals, i.e. the soot is burned off at high temperature. This happens either automatically while driving or as a controlled regeneration. If the machine is used for short, cold work, the filter cannot reach regeneration and becomes clogged. AdBlue must be clean and of the right quality — contaminated or diluted AdBlue, or a sensor and metering error, typically triggers warnings and eventually a power limitation that forces the machine to the workshop.
When you understand the relationship between operating temperature clean combustion and after-treatment – and know the requirements for F-gas certificate and legal emission cleaning – you can keep modern machines in operation without breaking environmental rules.