I'm in the process of replacing all the brake pads on my '85 240 and doing a complete system bleed/flush with new brake fluid. I don't have a pressure bleeder and I've read the archives here about the piston in the junction block moving while the brakes were being bleed and causing seal damage.

I have both the Haynes and Bently manuals. The Haynes simply says to remove the switch from the warning valve giving few details how to do that. I could find no reference in the Bently manual about removing the switch before bleeding the brakes.

So my question is, will removing the plastic cap from the junction block and disconnecting the wires to the switch prevent the piston from moving while bleeding the brakes? I have the feeling that if the piston moves, the junction block on my '85 will be toasted and I don't want to drop another $100 for a new one if I can prevent damaging the one in the car.

BTW, I removed the master cylinder reservoir and dumped the old fluid and cleaned out as much crud as I could. Cleaning the rear section was a major PITA! I couldn't get it all out but I got most of it and the reservoir looks much cleaner. I reinstalled the reservoir and filled it with fresh DOT4 brake fluid and I'm ready to start bleeding the rest of the system but don't want to start doing that until I have a clear understanding about the actuator safety valve.

Thanks in advance!

DeWayne