As soon as I start my car there is a intermittent audible thumping/knocking sound that last for about a second. It seems to be coming from the right side of the engine. It sounds like something is stuck and is being forced open like a vent. I took it to my dealer and he ran diagnostics and could not duplicate the problem. Is it also normal to hear mechanical sounds when you turn on and of HVAC controls?

[SIZE=1][SIZE=1][SIZE=1][SIZE=1][SIZE=1][SIZE=1]I cannot advise on the engine knocking but I would like to comment on your question # 2 -> HVAC system noise.

What kind of noise do you hear ? "Normal" noise is :

1) A soft clicking noise caused by the blend door actuators (stepper motors). This noise should be gone after a few secs. when the actuators have reached their set point positions. It may come back from time to time when new door positions are commanded by the HVAC control unit.
2) A sizzling noise (so called TXV hiss) which is caused by the high pressure refrigerant getting released into the evaporator. This is a cyclic noise, its frequency depends on the load and charge conditions of the A/C system.
3) Blower noise - which should sound clean w/o any whistling / knocking / grinding / ... elements.

The car manufacturers try to reduce the noises to a minimum but there is no such thing like 100% noise suppression.

If you hear something else than one of the components of your HVAC system may have a problem. Can you post a more detailed description ?

Richter,

Thanks for the response. It's more like an actuator sound maybe that's it? If you read the Car&Driver report on the T5 it's I think the same type of sound. I will taking my T5 in for a service soon and will ask them to check it out along with the squeaking noise coming from my front brakes.