Just borrowed a pressure tester last night and found a good sized leak myself on the lines heading to my throttle body. I was running distilled water w/ water wetter so I didn't have any obvious coolant lying around after the car was cool enough to hunt around in.
With the pressure tester we could easily hear and then eventually see the active dripping.
A few things to check:
- replace you rad cap - just do it, it's cheap
- check to see if your water pump is weeping coolant (suggests a bad water pump)
- borrow / rent / buy a cooling system pressure tester and make sure your cooling system holds at least your rad cap pressure rating
- when the car is cool, take off the rad cap, and put in a funnel that fits tightly to where the rad cap goes. Start the car and watch the coolant level rise. Burp out air if there is any. If air is continuously showing up, it suggests a bad head gasket. Don't overheat the car with the cap off, this is just to test for air pockets or air production while the water pump is moving coolant.