Was the water pump replace *before* or *after* the problem of running too cool developed?

 

Wow, two people with the exact same rare issue at the exact same time. God is laughing I guess.

It must be bypassing the tstat somehow or it's not closing completely. An engine would overheat if the tstat never opened and would never heat up if it stayed open. But you know this since you're a mechanic.

 

Have not idea what was wrong checked thermostat in boiling water, worked fine. Replaced with new 195 degree thermostat with jiggle pin in it, replaced fan clutch again, and flushed entire cooling system again. Filled with antifreeze like before, started engine, coolant temperature showed 135 immediately on Bosch scanner, let run for about 5 minutes at idle and temperature started to climb rather quickly. Accelerated to 1500 rpms temperature dropped, brought rpms back to idle, checked radiator and definitely thermostat had opened coolant level had dropped, topped off coolant put radiator cap back on. Repeated to raise engine rpms to 1500 for about 5 minutes temperature climbed and dropped, brought back to idle. Repeated a couple more times and amazingly temperature reads about 199 to 205 with scanner and on temperature gauge. Everything works like normal.

 

Gotta love the easy ones.