JMW 0 Report post Posted August 9, 2017 Just changed the serpentine belt & impeller on my 250 CR, Volvo 5.7, the motor always ran @ 160 degrees. Now it warms up to 160 but as I accelerate to plane the temp slowly drops to 125 degrees, once I slow to idle it will rise back to 160. Never overheats and runs smooth. Any ideas? Quote Share this post Link to post Share on other sites
jfed 0 Report post Posted August 9, 2017 Sounds like the thermostat is stuck open. Quote Share this post Link to post Share on other sites
stouchton 0 Report post Posted August 9, 2017 Thermostat sets minimum operating temp - I would change thermostat and NOT use automotive grade. Quote Share this post Link to post Share on other sites
BrianNJ 0 Report post Posted August 10, 2017 Likely the thermostat is stuck open. Maybe it has something lodged in it, or maybe it is just worn. I don't know the spec for your engine, but most are supposed to run at about 175F. I recommend replacing your thermostat. Quote Share this post Link to post Share on other sites
