Corolla 07 2.0 D4D Trickling/rushing water sound behing dash

[timorridge]

I'm not one to post ailments of cars often, I can live with slight niggles but this one is driving me nuts.

My Corolla of which I've had two months has a sound from behind the dash which sounds like running water through the heater. It only does it at a standstill and in first and second gear at approx 2000rpm. I initially thought that it was creaking trim but after removing the dash facia to reveal the heater its clear it coming from there. I did the 'burp' to try and expel any trapped air pockets of which noting seemed to expel, this was done by raisng the radiator over the heater core on an incline. The heater is working as normal, the temp gauge sits level and the car drives fine. The only other option is to do a coolant flush I guess.

It was sold to me with a replaced cambelt and water pump, I wonder if trapped air has got in the system from a refill?

Ive attached a link to a video where you can hear the rushing water.

http://1drv.ms/14IQgAL


Any ideas or helpful advice I can consider please?

[timorridge]

I don't think its related to air con as it does it when air con isn't running.