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I can’t quite grasp why a mechanical seal is used on the coolant pump. It seems complex. Why not a double lipped radial seal - like an oil seal?

biltonjim wrote: I can’t quite grasp why a mechanical seal is used on the coolant pump. It seems complex. Why not a double lipped radial seal - like an oil seal?

There are 4 things to consider when selecting sealing media.
1st is the temperature of the fluids or mating surfaces that the seal will be subjected to. In this case fluids at temps as high as 110 deg. C.
2nd - the type of fluid to be sealed, Could be corrosive or alkaline or petroleum based
3rd- is the pressure differential across the face of the seal in this case as high as 12 psi.
4th- the linear speed of the seal face to in this case the drive shaft of the pump.

A lip seal could take the rpms of the drive shaft provided that the differential pressure was under something like 5 psi and sufficient flow of fluid to take away any heat generated at the sealing face from friction but when combined with the heat of the coolant and a coolant pressure of 12 psi, would likely fail. Most of the elastomers get really soft at elevated temperatures.

Thank you for the comprehensive explanation, Kawboy. Your depth of knowledge is unfathomable.

biltonjim wrote: Thank you for the comprehensive explanation, Kawboy. Your depth of knowledge is unfathomable.

Retired 10-1/2 years now and this is all carry around knowledge that's clogging up my RAM. Time for a core dump I think.