Oil in the coolant
An oily film in the expansion tank needs investigating. A photo can show what it looks like, but cannot tell where the fluids might be mixing or whether the residue is from a previous fault.
Where oil and coolant might mix
On engines with a liquid-cooled oil cooler, an internal leak in the cooler can let the fluids mix. The head gasket, cylinder head and other possible leak paths may also need assessment. We take into account the engine’s design and the fault history before discussing what to check or remove.
If there is a temperature warning as well
If the engine warns of overheating, stop as soon as it is safe and switch off. Keep the coolant cap closed while the engine is hot. See cooling system faults for what may need checking.
What to mention in your message
Tell us when you noticed it, whether the coolant level has changed and whether the system has already been repaired or flushed. That helps us plan the diagnostic checks.
Start by telling us about the fault
Open WhatsApp, review the suggested message and decide whether to send it.