The expansion valve is located under the dash directly above the accelerator pedal. The kick panel under the instrument panel must be removed to expose the valve for R&R. There are four phillips head screws holding the panel in place as well as a plastic clip that fastens into the center console. The expansion valve is high up between the steering column and center console and is covered with foam insulation. You will find four tube fittings leading to the valve, two on the top side and two on the bottom. It will make the job much easier of replacing the valve if you have flare nut wrenches. The two largest fittings require a 15/16" wrench. Remove the smaller fittings first then tackle the large ones. Try replacing the expansion valve first, if no help, then please e-mail me and I'll send you instructions on removing the dash for the rest of your work. Hope this helps!
'67 250SE Cabriolet
'93 300E 2.8