Mk6 Coolant Smell

[hazbaz1984]

Have that lingering sweet smell of coolant seeping out from under the bonnet when the engine is hot, outside of the car. 

No visible leaks. Coolant reservoir still has plenty of coolant in it. No overheating issues. No white smoke from exhaust. No mayo. No exhaust gasses in coolant tank. 
 

What are the most likely sources of a minor leak of hot coolant that would produce that easily identifiable smell?

[hazbaz1984]

Should say car is a 2006 1.4l petrol. 

[unofix]

Coolant expansion tank will have hairline cracks in it. A very common problem with the older tanks. See eBay for replacements, should be about £25 Also replace the filler cap at the same time.

[hazbaz1984]

Champion. I’ll give that a try. 

Tank does look a bit crazed. It’s been through a lot I suppose. 116k. How ever many 1000s of heat cycles.