944 cooling system refresh: what owners should plan for
Age-related cooling failures on a water-cooled transaxle car, and the order to work in.
Cooling problems on a 944 are usually about age rather than design. Hoses harden, plastic radiator end tanks become brittle, and the water pump and thermostat reach the end of their service life around the same time.
Before replacing anything, pressure-test the system and look for coolant staining around hose clamps and the water pump weep hole. Then inspect the radiator core and end tanks — a radiator that has been run with poor coolant is a liability.
When you do refresh the system, work in one pass: radiator, hoses, thermostat, water pump and a new coolant fill with the correct bleed procedure. A cooling system that is only half renewed tends to fail at the part you skipped.
Finally, check that the cooling fans actually cycle. Electrical faults on an older car can mask a healthy cooling system, or hide a failing one.