Troubleshooting A Weak Brake Booster When Installing A Demco Stay-IN-Play In A 2022 Ford Bronco

Question:

This is a followup from an earlier question re: moving a Demco Stay-In-Play duo unit from a jeep to a bronco: I installed the Demco unit, etc, from my Jeep onto my 2022 Bronco. Everything works as before, except I dont seem to be getting vacuum boost from the Broncos booster when I test the Demco unit. For example, pulling the breakaway switch causes the air cylinder to pull slack from the cable, but does not depress the pedal at all. Same thing when calibrating the system per instructions. Vacuum boost works perfectly during normal vehicle operation. I had a minor intermittent vacuum leak when I first installed the vacuum fittings Demco #6257 vacuum connection kit but proper hose clamps solved that issue. So the Bronco vacuum booster is working, and the air cylinder seems to work. The air cylinder hose is the same one removed from Jeep. I did not change or remove any existing check valves when I installed the vacuum connection kit, although a reversed check valve would likely cause this problem. Im thinking either a vacuum leak, which I doubt, or a vacuum pump problem. How can I test either of these? Or do you have other ideas? Regards

asked by: Dennis R

Expert Reply:

Demco does have it listed that in Ford 2015+ vehicles that it's best to install the vacuum connection directly to the sensor port of the brake booster using part # DM6257. Most likely the issue you're facing is just caused by your connection to vacuum line.

You can test the vacuum line for a leak by starting the engine and switching it off after 10 seconds. After 10 minutes of standstill, depress and release the brake pedal several times. With each new press, the pedal should be firmer. If the pedal doesn't become stiff, there is a leak in the line.

A reversed check valve could also cause the issues you've been having so you'll want to recheck your setup and ensure that the black end of the check valve is inserted into the main unit and the clear end is connected to your line.

expert reply by: Kevin C