Occurs intermittently. Never overheats. Pressure tested the system and found no leaks. No accumulation under car after parking. I'm totally bewildered!!

I have to constantly use coolant every 2 weeks $17.89 and paid 258.00 to stop roaring noise and clicking sound when I turn and it still does it. I constantly smell gas, engine pressure problem etc

Update from Apr 26, 2011: I've replaced a motor with 85,000 miles and still continue to buy antifreeze since 2010 current now imagine spending over 30.00 a week depending on how much you drive it within that week