Not all vacuum wiper motors will have that nipple, but on the ones that do, it's a quick, easy fix. The solvent gets drawn through the motor, and cleans and lubricates all the moving parts. Then it gets drawn into the intake and burned- - - -no muss, no fuss! On the ones with the tiny intake holes instead of the nipple, spraying WD-40, PB Blaster, or KROIL into the vent with the motor running will accomplish the same thing.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!