Join Date: Nov 2000
Thanked 0 Times in 0 Posts
Re: CJ 7 Brakes
If there is a leak in the intake system and lines, it would make it idle rough. Try pinching off the line to the booster and other lines one at a time. If that changes the idle speed there is a leak in line or booster. If pressing on the brake pedal changes the idle speed, there is a leak in the booster and it needs to be replaced.
A good booster should hold vacuum, such that you can shut off the engine, and depress the brake pedal once, and still feel assist. After pressing it a few times, all the vacuum bleeds off and it has no more boost. The pedal should now be stiff. While holding pressure on the pedal, start the engine, as soon as it starts idling, you should feel it pull in the boost. If it fails the above, or the problem is intermittant, then I suspect it is the booster and it needs replacing.