Small M3 details. Back in the day, most cars and trucks used engine derived vacuum air to power the window wipers, the M3 was no exception to this rule, being designed in the 1930’s. Here are the original units, one complete, and one mostly taken apart. These use a tilting valve system to apply vacuum air to one side and then another in the semi circle air chamber, with a leather baffle in between. This baffle was then connected to the wiper rod … pretty cool!