Coolant level

[teecee90]

The cap is an on/off valve but it shouldn't leak it will allow coolant into the expansion tank, via the expansion pipe.  If the cap is leaking, in turn the expansion tank will try and replace the lost coolant and will either be empty as too much needs to be replaced or or lower, but as the cap leaks over time it will empty.  Unless you add water which in itself is telling you, you've got a problem.   

The clue is in the name expansion 

If the rad cap is leaking you will have traces of dried coolant around the rad cap, no matter how small the leak, it will be there and if the cap it leaking the system will no longer be pressurised so will run hotter.  Depending how bad the bike will boil or overheat. 

Presumably the valve within the cap could fail but the upper seal remain intact? That could presumably result in no leakage from the radiator cap but 'blow off' of excess coolant through the valve at a lower pressure than specification. The excess going into the expansion tank and ultimately out through the overflow if enough of it?


On the gen1 the cap is not just a cap, it is also a valve (with a specified pressure rating). Not sure about the Gen 2 though....