After I replaced the front brakes on my F-150, and lowered the truck on the jack to drive away, I saw a LOT of white smoke blowing out of my tail pipe. Nothing smells burnt when this happens - no burnt oil smell or anything else, and water drips out the tail pipe. Another problem I noticed at the same time is that the brake pedal goes all the way to the floor when I'm braking, and when it gets to the floor, I can hear gurgling or bubbling. This is coming from behind the firewall approximately where the master cylinder is located. Also, once the brake pedal reaches the floor, more white smoke is coming out the tailpipe.
I think I know exactly what is happening. Right behind your brake master cylinder is where the power brake booster is located. This booster is acted upon by engine vacuum in order to make the pedal easier to press down.
Since the booster is acted upon by engine vacuum, this means that it is connected to the intake manifold of the engine. If the rear seal in the brake master cylinder has failed, this will allow brake fluid to enter the power brake booster and would be the reason the pedal travels all the way to the floor; the rear seal is preventing any hydraulic pressure from building up in the master cylinder.
With brake fluid inside the power brake booster, the intake manifold is able to inhale the brake fluid into the engine whenever the brake pedal is depressed. This would be the cause of the white smoke. I would recommend having the brake master cylinder replaced, and having the power brake booster replaced by a certified mechanic. YourMechanic offers mobile technicians to come perform services just like this at your home or office.
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