You can't trust the temp gauge when there are severe head cracks. The excess pressure does strange things to coolant flow and the single point of reference is not a good indicator.

Are you sure the AC compressor is installed properly? It might be sitting at an angle putting undue loads on the pulley and clutch. I'd say check the tensioner idler pulley but the power steering pump isolates the AC compressor.

Sixto
95 S420
87 300SDL