Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Changeover valve, low temperature EGR cooler: Notes
The changeover valve is integrated into the coolant hose towards the low temperature EGR cooler.
The high-pressure exhaust gas recirculation is a measure to reduce the formation of nitrogen oxide (NOx ). Nitrogen oxides are created in great quantities when combustion runs with an excess air and at very high temperature. Here, the oxygen combines with the nitrogen of the combustion air to form nitrogen monoxide (NO) and nitrogen dioxide (NO2 ). On the diesel engine, exhaust-gas recirculation is sometime required at idle speed and always in the partial load range, because a particularly high excess air is used there.
For the cooling of the exhaust gas for the high-pressure exhaust gas recirculation, a low temperature EGR cooler is used. The EGR cooler is integrated on the cold side after the radiator. As a result, the routed back exhaust gas can be further cooled down.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.