Have a refrigerant leak on a 93 300E. I have not been able to locate the leak visually with dyes or with refrigerant detectors. The only place left is the evaporator and I was wondering if there is a sure fire way to find a leak there or is it just a matter of elimination. I have been told by the dealership it would cost around $2000.00 to have it replaced. So I want to be very sure of where the leak is before I dive into this job. Thanks....