I have a problem I haven't seen before. If you press either brake pedal it will bog or kill the engine. Mostly on the brake only pedal it does this more. And on this lift the brakes are part of the hydraulic system and so the problem only happens when the brake control valve starts to get moved up. So there is no master cylinder on this system and the brakes are operated buy the brake control valve that is located under the floor panel on the left side. I have pulled this valve off and kind of checked it out and checked out the check valve on the side of it. But haven't taken it all the way apart and didn't see anything that look wrong. And the brakes work fine still.