A little over a month ago I got head work done because my timing belt snapped on the freeway and my valves got bent. I also had to replace the o ring to the oil cooler. About two weeks ago I noticed my coolant level started to drop. I have to keep putting in coolant every three days it seems and I also smell coolant when the car warms up through the ac vents. My cooling system has been pressurized to look for leaks but nothing was found. My vw mechanic told me that it could be leaking into the head, but my oil is not milky and my coolant does not contain oil either. He finally suggested that it could be the coolant bubble (it is old and dirty). What are you guys take on this? Anyone else experience this mystery?