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Old 04-27-2020, 06:55 PM
  #12  
SweetD
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Join Date: Oct 2004
Location: RI
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Could also be your water pump impeller. If it has not been serviced in awhile, the rubber impeller "arms" get deformed into a permanent shape that allows air to pass through with some water. This prevents enough water from getting up into the cooling passages, especially at higher RPMs.



See how curved the couple of arms are in the rear of this pic? Different from the rest. That's what I'm talking about. They allow air in with the cooling water.