I have been eliminating a few issues on my newly aquired '87 300D Turbo. Temps have been in the upper 90's here for the past two weeks and out on the open road the car runs warmer than I would prefer, usually 100C and will creep higher at idle(no higher than 110C and all this with the A/C operating). I am not comfortable with these temps.

I have checked the fan clutch for proper operation and according to information gained through the search feature here I have ruled it out as the cause.

I had the radiator "boiled" out by a qualified rad shop. The rad tested great for airflow and coolant flow after the service but didn't solve the problem.

Aux fan works but I need to replace the 3-pole high speed switch because it is no good. Switch is currently grounded and works continuosly.

I couldn't find exactly what I was looking for so I must post this. My thought is that the t-stat is possibly stuck open or broken and the system cannot properly cool the coolant fast enough. I went out tonight and was looking around the engine compartment and squeezed the upper rad hose and could hear a clicking noise from the t-stat housing. Should I be hearing a noise from that area? I know anything is possible but could the t-stat be broken and causing the engine temps to be higher? Sure sounds like something is loose in the t-stat housing.

Kevin