(31 Jul 2014, 2:01 pm)Robert wrote 4941 may possibly be taken off the road. The coolant is smoking and the leak is quite bad. Not a bus mechanic but I would say that this shouldn't be happening?
Modern (current) cooling systems rely on pressurisation to prevent the coolant from 'boiling' (temperatures are typically in excess of 100 degrees C).
If a leak occurs, the escaping fluid will vaporize (ie 'smoke') as it 'boils' in the atmospheric environment (ie not contained and pressurised).
What you are seeing is steam.
It is because of the pressurisation that care should be taken when dealing with cooling systems as the fluid is likely to be very very hot (ie above boiling).
But you are correct - it shouldn't be happening.