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Blue or white crystallised residue visible on engine components, indicating a coolant leak. Very common on BMW N-series engines. This fault code is stored when the engine control unit detects a specific fault condition. Common causes include sensor failures, wiring faults, and component wear. Always read additional fault codes before replacing parts — multiple codes together provide a clearer diagnosis. Clear the code after repair and test drive to confirm the fault does not return.
Based on 0 driver confirmations
No commonly reported misdiagnoses for this fault yet. If you have replaced a part that did not fix this BMW problem, submit a wrong diagnosis report — it helps other drivers avoid the same costly mistake.
Noticed blue crystallised residue around the thermostat housing. It had cracked and was seeping coolant. Replaced the plastic housing with an updated part. Also pressure tested the rest of the cooling system and found the expansion tank had a hairline crack too. Did both at the same time.
Parts replaced: Thermostat housing, expansion tank, coolant
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