Overcooling at high rpm

[andsoko]

I have a weird overcooling problem with 4.3L V6 1995 engine. Temperature is fine (around 150-160F) if rpm is below 1500. But as soon as rpm is in 2000-4000 range the temperature drops very fast (within 20-30 seconds) to ~ 100 F. When I decrease the rpm to 1000 or idle speed temperature returns to normal range within 2-3 minutes. I replaced the thermostat and the impeller. It did not help. What else can be wrong?

 

[RicardoMarine]

A good working thermostat shouldn't care about engine speed. It's job is to hold back coolant (seawater if RWC) until engine temperature tells it to open progressively.


I would take a temp gun reading to see if the temp is actually dropping, and/or to see if you have an issue with your gauge or sending unit.



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