My 3.0-litre Isuzu turbo diesel has done 125,000 km. It has always been serviced by book, and runs faultlessly, but the coolant looks scummy and smells a little like diesel. Does the coolant go off, or is it possible for diesel to get into cooling system?
Coolant should be changed regularly, annually at least, but the interval should be shown in your service book. It can look a little oily, but that's not a problem, and as your vehicle is running well with no sign of a problem I wouldn't be concerned, but do change the coolant.
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