Do not drill holes in the thermostat! One of the modes it operates in is bypass, drilling holes will defeat bypass!

You can check the temp gauge with a infrared thermometer by aiming it at the temp sender on the block. Also aim it at the upper rad hose and the lower rad hose and report all numbers.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked