Was attempting to change the coolant yesterday in my 06 GT using the Airlift system. Compressor 120-150 psi, hooked up the Airlift system giving me a tight seal on the intercooler degas bottle but was unable to pull coolant despite having good vacuum. Left the Airlift in place thinking it was due to the large reservoir of coolant and just needed time to compress hoses and pull out coolant but was unsuccessful. Is it necessary to drain the front radiator via the petcock prior to using the Airlift or do most of you skip this? I understand I'll be only able to get approximately 80% of the system's coolant out via this procedure. My other thought is a defective venturi valve? Thanks for the assistance.