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Discussion Starter #1
Hello all!

A recent issue has sprung up with my 2007 Focus ZX4 with the 2.0 Duratec. A few weeks ago, my driver side brake caliper was seizing up while driving, wouldn't let go from a stop. Got it to my repair shop and they replaced both front calipers (were factory), rotors and pads & changed/replaced brake fluid. I thought all was good, however, today they started seizing up again while I was holding the brakes in a drive thru. I was baffled as to why, and I tried pumping the brakes while the car was both on and off; nothing, they were still sticking. I tried thinking of any variable I could change, and what came to mind was that my defroster/compressor was on and running. Once I shut that off, the brakes were 'okay' to limp to the shop I had the work done at. At first I thought it was maybe my master cylinder, but now I'm thinking it may be a vacuum issue somewhere. Also, my SE model does not have ABS. Any insight into this would be greatly appreciated, as I am stumped.

edit car has 138,9xx miles

Thanks!
 

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Ever think it might be the backs instead?

And why pump brakes, that makes the seizure even harder.

A vacuum issue cannot make brakes seize more, it would do the opposite, all retraction of pads/shoes is mechanical........
 

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Discussion Starter #3
Appreciate the reply!

It's not the backs, as the fronts have been groaning and smell like burnt carpet upon doing so. Only reason I pumped the brakes was to see if they would retract; couldn't possibly do any worse as they wouldn't really let go. If theres no vacuum issue, I'm wondering what mechanically can be going wrong, as the calipers were deemed the issue the first time and these are brand new
 

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...what came to mind was that my defroster/compressor was on and running. Once I shut that off, the brakes were 'okay' to limp to the shop...
That makes me think that a vacuum booster issue may be to blame. Turning off the A/C would likely increase the vacuum a little bit when idling. But, I don't know if a defective/failing vacuum booster can cause the calipers to seize. Never heard of that happening!
Hopefully they examined and lubed the caliper slider pins when they installed the new calipers. There is nothing to retract the calipers, so if the slide pins are not well lubed the calipers can stick. The movement of the rotors is what pushes the pads/calipers off the rotors.
 

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...Hopefully they examined and lubed the caliper slider pins when they installed the new calipers. There is nothing to retract the calipers, so if the slide pins are not well lubed the calipers can stick. The movement of the rotors is what pushes the pads/calipers off the rotors.
That’s exactly where my mind first went. It’s an easy & quick thing to check. There are LOTS of YouTube videos that walk a first-timer how to remove, inspect, and lube the slider pins.

Worst case scenario is you buy new slider pins and a bottle of brake lube at the nearest auto parts store for $20 and know that piece has been ruled out just as you can now rule out faulty caliper pistons.
 

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Just FYI... You said that they replaced your calipers. Often the new calipers come with the slide pins and are already lubed. But sometimes they don't.
 

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Not power booster, all they can do is leak. There is nothing in there that can stick brakes on to lock if on release the pedal comes back up. All the text there says is that a/c on is causing idle rpm to drop enough to affect booster vacuum total amount. Due to older higher mileage motor. You can change booster all day long and not change that and these cars are known for it. Then the brakes appeared to not seize because they were applied with less pressure to begin with. Often with seizing brake it is the very last part of the braking force that locks the parts in place.
 

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If the booster or master has been off and the rod sticking out of booster has had the tip extended out too much that can DEFINITELY make brakes stick on. That tip length is critical.
 

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I had an older Escort that was indeed applying the brakes because of the vacuum booster. It is possible.
Also, the rubber hose can plug. I've seen that on two vehicles.
 

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The tip length I just mentioned. It's a dead art; mechs today have not clue as to what to do with it. If out too far your mech messed up, he is supposed to check/adjust it. Too far out puts the brakes on instantly.

If the rubber hose plugs you have no power assist at all.....er, NO brakes. Pretty hard to miss that. More likely somebody missed the function of the one way check valve in the line to misdiagnose. Common among lunkheads, they will find they are plugged up on every vehicle on the planet.

So much of this stuff was known in the '60s but is fake news now to mess things up. Then people buy countless parts that are 'bad'. I saw it enough to make you throw up.
 
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