Check valve between vacuum pump and wiper motor

This is how the vacuum drive of the wiper motor works

The function of the non-return valve is that the vacuum pump, which is screwed under the engine's oil pump, builds up a vacuum at higher revs, from there a vacuum pipe opens onto the passenger side of the engine block. There, on the outside of the engine block, the non-return valve MOT-5458 is threaded. At the top of the non-return valve tube is a vacuum hose that goes to a distribution block on the torpedo wall, from there a vacuum hose goes to the engine's intake and a vacuum hose to the wiper motor. The function is such that at lower engine speeds you have a lot of vacuum from the intake which then drives the wiper motor. Then at higher engine speeds, the vacuum in the intake is lowered at the same time as the vacuum pump under the oil pump spins faster and starts to build up a higher vacuum which then drives the wiper motor. So the vacuum pump drives the wiper motor at higher speeds, at lower speeds the engine's intake vacuum drives the wiper motor. The function of the non-return valve is that when the engine runs at low speeds, a large vacuum is formed in the intake and then oil would be sucked up through the vacuum pump and further up through the pipe to the distribution block on the torpedo wall and on to the engine's intake and burned with a substantial oil plume development in the exhaust gases, therefore man the non-return valve that prevents it.

               Here is a quick sketch of the function of the vacuum drive to the wiper motor.