I've been having to top up my coolant every now and again, approx 0.5L per 500 miles, but couldn't see any evidence of a leak until today after I'd returned from a decent motorway run. (I was suspecting a possible HG issue, so am quite relieved!)
I have a small amount of coolant sitting on the ridge around the top of the expansion tank. This then drips down onto the undertray where it evaporates. There is no evidence that coolant is being sprayed around under pressure, it just seems to collect and drip.
You can see the coolant collecting in the above picture.
I've read about problems with the expansion tank hairline cracks, but I can't see any obvious cracks and as the coolant is collecting at the top of the tank well above where the usual hairline cracks appear. I can't see anything obvious from the other suspect - the top coolant hose.
I know the general advice is to replace as much as possible, but the car is a cheap runabout so I don't want to throw money at it in an effort to get rid of the problem through trial-and-error.
BMW have quoted me £33 for the top hose and £74 for the expansion tank; does this seem reasonable? Any pointers to good online retailers for BMW OEM parts?