OK well this morning i got the thermostat changed on the A4 tdi 1.9. Now the guy that did the job changed the stat then left the car running , the temp gauge did not move from its original position. He then proceded to pull off the expansion tank hose where no water was coming out. Long and short of it was he told me it looks like the waterpump is done and needs changing as the top hose is cold. So i drive off not happy thinking ive just bought a dud car and just like magic the termp gauge reaches 90 and stays at 90. The top rad hose they said was cold due to the waterpump working is now warm as it should be and everything seems perfect. Now in the back of my mind im thinking i need a waterpump , but do i? Have they dioginosed the problem correctly (bearing in mind i know these guys)? Has the waterpump developed a intermittant fault ( but i was under the impression with it being belt driven it either works or not) Could it be a airlock issue?