I am about to tackle repqairing my AC my self on my 83 300SD and feel pretty confident except for one last part. After I re-install the compressor, drier, and expansion valve with new o-rings and ester oil, where do I connect my vacuum pump to dry out the entire system? I found a cheap vacuum pump at Harbor Freight (http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=92475) and thought it would be better than no vacuum at all prior to filling with 134. They mention hooking the vacuum fitting to the car's "drain port". What is this drain port? Also they have a fitting on the vacuum but no tube or quick connect to the car. Do they mean hook the vaccum to the drier, 134 high side fitting, low side fitting? Ahhh... I guess I am just a little "green" here!