Just taken my Sti for a blast and when opening the bonnet when I got back I got a whiff of anti freeze which was coming from the rad cap (not the expansion tank). There did not seem to be any fluid leaking so I assume its just the engine releiving pressure from the cooling system, is this normal or is the pressure build up due to an underlying problem?

 

Mine often has a sweet smell after a hard drive or lot's of traffic sitting!