Toyota Repair: coolant leak in 98 avalon, coolant leak, toyota avalon

Question
Ted: I have been experiencing a slow coolant leak in my 98 toyota avalon, a well maintained car.  the leak is away from the radiator, and somewhere near the firewall.  when I recently took it in for routine maintenance, the tech told me that it likely is due to a leak from the engine block itself [$600 repair], but he could not absolutely determine its source.  when I asked him how common this is, he said that mine probably would only be the second one he has seen with this problem.  I don't feel confident with his assessment.  what do you make of it, and do you have any idea where a common source of a leak in my model may be?  thanks much!  pete

Answer
I would advise that you have a toyota dealer diagnose the leak, I don't feel comfortable with that assesment either, a couple of things made red flags pop up, if he's not sure where the leak is why is he giving you a $600 estimate to repair it? Repair what?
If it's the second one he's seen with this leak, how did he fix the first one?
Unless you really trust this guy you need to get a second opinion.
The best way to find a coolant leak is to pressurize the system and check for leaks, there is no guesswork, the leak has to be found and a recommendation made as to how to repair it, not "It'll be $600 but we can't determine the source" just doesn't sound right.