1994 E320 wagon has recently started to overheat. Usually runs at about 100 now creeps up toward red line on easy highway driving in cool weather in about 10 minutes or less.
Both aux electric fans operate when temp exceeds 105. Turning on defrost will drop temp back to normal then starts to climb again. Troubleshooting to date: Read all forums on topic. Fan spins freely even after bringing up to operation temps but I have reason to suspect something besides the clutch. I read that the clutch engages when heat off the radiator activates the bimetal strip on the front of the clutch. Before ordering and changing the clutch, I felt the front of the clutch and the radiator after it comes up to high temps and both the radiator fins and bimetal I can feel are cool to the touch. All radiator hoses are hot but the coolant in the overflow resevoir is cool. I removed the thermostat and the condition remains the same. How can I determine if there is enough coolant flow through the radiator to produce the heat needed to operate the fan clutch? Any Help or Speculation appreciated.