Review on Improved SEO: Motive Products 105 Brake System Power Bleeder by Mark Erandio

As others have said, the master cylinder cover can lose its seal midway if the J-bolts are over-tightened. It is difficult to tighten the bolts enough that they are tight enough to hold the pressure at the edges but not so that they flex easily and leak in the middle. I'm talking about GM master cylinders. Maybe wider isn't a problem. However, as with others out there there is an easy fix. Buy a pair of 6" C clamps from a discount tool store and use them to hold the cap in place. Don't over tighten. You can then inflate the tank to 15psi and it will work great once you ditch the J bolts and chains and go for the C clamps and you have a great tool that can do anything the more expensive ones do.