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I'm the new owner of an M20F, with vacuum actuated retractable step. The step didn't retract and the vacuum line had been plugged. The problem, of course, is that the rubber actuator boot had broken. In my case, broken in half, the half that fit over the retraction cylinder, and the half that reached over the piston. I suspect this is the typical break, as the rubber "boot" has to invert at each retraction. The first try was to use only the cylinder half, put a plastic bag over the whole thing, and start the engine. It worked. Once. The step retracted, came back out, and never retracted again. The problem was that the piston part fell off of the cylinder part, lost it's alignment with the cylinder, and was doomed to to jam instead of sliding up into the cylinder. The fix? Of Course. Duct Tape. The idea was to extend the rubber cylinder boot far enough so that it supports the piston and hold it aligned with the cylinder. One wrap of duct tape was enough. First, I wrapped some upholstery fabric around the piston, enough so that it would stretch the boot a bit when the boot was stretched over it. Second, a plastic sheet placed over the upholstery fabric. (I used a reusable grocery bag.) Third, the boot stretched over the wrapped piston. This is the form. Next: very loosely wrap one layer of duct tape around the piston form, overlapping the boot and extending the cylinder an inch and a half or so. Remove the piston form. The plastic will stay with the boot because the sticky side of the tape is stuck to the plastic, not to the upholstery fabric. Trim the excess plastic, that is, all the plastic not stuck to tape. This SHOULD yield a boot-half that is now long enough that the piston will not "fall off" of the rubber/tape cylinder when the step is extended. It is important that the piston slide easily in the new, longer boot-half. If it's own weight will not slip the (unwrapped) piston through the new tape and rubber boot-half, then the upholstery fabric was too thin, or the wrapping too tight. Try again. I got it on the second try... Lastly, reassemble the whole business, placing the whole assembly in a plastic bag. I used a tropical fish bag. Not the smallest, but the next size up. It was plenty long and wide enough that it fit over the metal cylinder. Wrap electrical tape around the bag/cylinder to make the seal, making sure the bag is loose enough when the step is fully extended. It's fixed. Engine vacuum will suck the air out of the big plastic bag. The piston will suck into the cylinder. The rubber/tape boot will invert. The step will come up as long as the vacuum holds. The weight of the step will extend it, and the tape/rubber boot will hold the piston in alignment with the cylinder. An AI will probably not sign it off, but the step will retract and extend. I don't know for how long, but for a while, I think. I hope this made sense, and I also hope you've got enough parts...