Originally Posted by
rebuilder86
the fact that it was fine until driven on freeway suggests the thermostat was possibly maxed out during the hot fast freeway drive.
its not a good plan to begin thinking the gauge is wrong and feel any comfort from that, because usually they fail the other way, they under read. ( wax doesnt expand anymore due to a leak or corrosion and resistance stays high; gauge reads low) And if it was reading midway between hot and normal, it may have been always overheating.
i wouldve removed the thermostat and checked the coolant flow visually in the radiator cap before buying a new pump.
u remove the t-stat, reattach housing, fill system with clean water, start car and watch radiator top tank for flow. if it overflows out the cap immediately, the radiator is too blocked. if there is little to no flow the impeller blades on pump have erroded away. if it flows nice well, u can consider the pump safe but cannot eliminate the radiator as a problem because it may be slightly blocked.
Any slight blockage does two things.
1. restricts coolant from being able to conduct heat to that blocked part of the radiator and
2. accelerates the flow of water through other unblocked sections which makes the flow too fast to successfully conduct heat into the metal for radiation. This is most pronounced during hot (high engine load) driving and higher engine rpm, where coolant is moving through radiator quickly due to the faster apinning pump.
So it has a two fold affect.
it would be wise to perform a full system flush with a "fast radiator flush" cooling system flush. these use strong acids and are not just a standard cooling system flush.
do this with ur old pump before replacing it.
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