My good o'l A6 (05 reg 3ltr estate) is blowing hot air out of the dash vents near to the doors. I'm guess this is due to one or other of the solenoid valves under the bonnet being stuck or faulty?

Anyway, I went to lift the 2 covers off to have a look but immediately got coolant leaking out. Is this to be expected or are my valves completely b......., er, due for replacement? I must admit the engine wasn't cold during the 5mins I had a chance to look ...