We often get complaints from drivers of “weak Jakes”. The coaches I work on have two speeds, high and low. First we verify that the jakes are in fact coming on. If they are active in both speeds, most then do a rebuild of the jakes. My question is, if the springs aren’t broken and the solenoid is working properly, is there any point of doing a rebuild? Keep in mind these are series 60s with over a 1,000,000 MILES.