A leaking EGR (Exhaust Gas Recirculation) cooler on a diesel engine can lead to several symptoms:

1. **Loss of Coolant**: A leaking EGR cooler can cause coolant to enter the exhaust system or intake manifold, resulting in a noticeable drop in coolant levels without any visible external leaks.

2. **White Smoke from Exhaust**: When coolant leaks into the exhaust system, it can produce white steam or smoke from the exhaust pipe, especially when the engine is warm.

3. **Overheating**: Coolant loss due to a leaking EGR cooler can cause the engine to overheat, as there is insufficient coolant to maintain proper engine temperature.

4. **Check Engine Light**: The vehicle’s computer may detect a problem with the EGR system and trigger the check engine light. Diagnostic trouble codes related to the EGR system may be stored in the vehicle’s computer.

5. **Rough Idle and Poor Performance**: A leaking EGR cooler can cause the engine to run poorly, with symptoms such as rough idling, hesitation, and reduced power. This happens because the coolant can interfere with the proper air-fuel mixture.

6. **Coolant in the Oil**: In some cases, a leaking EGR cooler can allow coolant to mix with the engine oil, leading to a milky appearance of the oil. This can cause serious engine damage if not addressed promptly.

7. **Sweet Smell from Exhaust**: The coolant contains ethylene glycol, which has a sweet smell. If coolant is leaking into the exhaust, you may notice a sweet odor coming from the exhaust pipe.

If you suspect a leaking EGR cooler, it’s important to have the vehicle inspected and repaired by a qualified mechanic as soon as possible to prevent further damage to the engine.

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