Just as a side note, my experience with the venturi type pumps is rather disappointing. It's better than no vacuum at all, and if it's about 100 degrees out (and low humidity) you probably don't need much vacuum to boil moisture. I suggest letting the vehicle idle for about 2 hours while vacuuming and lowering the hood to capture as much heat under there as possible in order to assist the weak vacuum in removing moisture.

You can get a 2-stage pump off eBay brand new for $150 and you'll surely get your money's worth on refrigerators, home A/C units, friends' cars, etc. You can also just rent one for free at AutoZone. I highly recommend you get a hold of one of these and do it right the first time. Any moisture in your system will turn acidic and start corroding things from the inside out. But I'm sure you know all that already.

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280