Quote:
Originally Posted by QB93Z
In both cars when cruising at about 55 mph in sixth gear (about 1600 to 1800 rpm, the coolant temperature will rise to around 225. If I shift to fifth gear, (>2000 rpm) the temperature immediately drops to around 203-205.
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Jim, I don't believe this is coolant bypassing the radiator. That should only happen when the pressure gets high.
I posted about this on the listserv a while back. I believe it is related to the flow capacity of the pump at low rpms. Graham Behan sent me a chart of the flow rating at various rpms, and mentioned it was likely that at those lower rpms, the pump does not flow enough. This is why downshifting helps.