I have the vacumn type set up on my 57 Chevy. Last week I started having a problem with the wipers working after using some engine degreaser and high pressure washer to help get rid of years of accumalated oil, grease, and dirt in the engine area. I didn't think of protecting the windshield wiper box from the spray. The vacumn hoses look good to casual inspection. At the same time I also adjusted the automatic Choke on the carb. I have no idea whether adjusting the choke would affect the wipers , but thought I would mention it. Remember I am in the learning stage on motor self-repair. Any direction on a possible cause or fix for the wipers would be appreciated. Right now I can turn the wipers on and they swing out and stop. I turn the switch off and they return to the start position. Every once in a while they will make a second pass before stopping.