566f00a7   
   From: mik@localnet.com   
      
   "Geoff"  wrote in message   
   news:e622a952-b3ff-48d0-a203-db99bc7b2815@e39g2000hsf.googlegroups.com...   
   > The situation: at idle, truck warms up normally, then after a fer   
   > minutes the engine temp gauge moves slowly up into the red zone, then   
   > suddenly drops back to normal, and stays there.   
   >   
   > The truck: 1985 longbed, 200K miles, 22R-E (fuel injected) engine.   
   >   
   > Maintenance so far. Cleaned radiator, replaced hoses, replaced fan   
   > clutch, replaced engine temp sensor, replaced thermostat. Coolant is   
   > at normal level, no sign of loss.   
   >   
   > Any ideas?   
      
      
      Sounds like either a bad sending unit or thermostat. You mentioned that you   
   replaced the "engine temp sensor". Being fuel injected, that engine has a   
   coolant temp sensor for the ECM and a temperature gauge sending unit that   
   operates the gauge. Are you sure you replaced the right one ? Have you checked   
   the coolant temp with a thermometer to see if is actually getting that hot ?   
      
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