Brake Booster and Brake Pads

Hi All,
I had my brakes replaced after a mechanic told me they were worn down (pads and rotors). Also had tires replaced.
Immediately after taking it out of the shop, I notiiced that something wasn’t right (hissing sound when press on the brakes), so I brought back.
Repair shop says this new issue is not something they caused, and won’t accept that it seems way too much of a coincidence that I never had that problem until immediately after repairs.
Repair shop said to do research and we’d talk after the repair, but I can’t find anything on whether in the act of doing the repair this is ust a coincidence, so I’m hoping you all can provide some insight.
He did mention that the new brake pads would make the booster have to work harder and break it, but the issue happened the very first time I pressed the brake.
Neither myself of the mechanic want to leave this with trust problems, but I can’t help but feel like the repair shop should at remove the new labor costs unless there’s a plausible explanation that this indeed is a coincidence.
Any help you can provide is greatly appreciated!

Car: Ford Edge SE 2008. 115K miles
Initial repairs done: New tires, Brake Pads and Rotors replaced, Power Steering fluid and cable replaced, New air filter.


Mechanic’s nightmare. A car with 115K miles comes in for routine service and a new thing breaks right out of the shop. Coincidence happens.

That said, is it just the hiss? Or is the pedal effort much harder to get the car to stop?

If it’s just the noise, give it a few weeks for the new brakes to bed-in and see if it goes away. I’d guess it will.

If the brake effort is much higher than before, accept the fact that the brake booster failed at 115K miles and pay the mechanic to replace it.

These bogus explanations never cease to amuse me…and do not help to alleviate trust problems…


Brake is indeed much harder to press.


If this is a bogus explanation, then the probability is astonomically unlikely to be a coincidence. As far as I’m concerned, this is the sticking point - if new brake pads stressed the booster. Otherwise, I understand it’s an old car, but there was no issue before the mechanics worked on it and then there was a new problem immediately after- not after driving off the lot- I mean it was there the first time I touched the brakes.


i’m not sure how new pads would stress the booster any more than old pads would.

I am a little concerned about the power steering ‘cable’ that was replaced, though.

It may well be a coincidence. But here’s the deal: If you lie to me when I’m questioning something that you did shortly before my stuff broke, and I catch you in that lie, I assume you broke it.

I’d have no problem insisting that they fix it for free. Why? Because they lied. Which means I assume they’re lying about everything, and so when they insist that they didn’t break it, as far as I’m concerned, they did. Even if it was unlikely that it would break.

Yeah, it’s unlikely the booster will get busted by a mechanic working on the brake pads, and that’s what they should have told you. That they chose to lie about what can cause the brake booster to break suggests to me that the intern drilled a hole in it or something and they’re trying to cover it up.

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Did you just check the hose to see if it was bumped loose or sprung a leak?

While I don’t appreciate bogus answers either, the point is you probably have a bum booster or at least a leaky hose that needs to be repaired. Would you have been happier if they would have called you half way through the job and said they discovered the booster was bad too? Really same result. The only question is whether you want to take it somewhere else to get fixed or fix it yourself. You are pushing the guy in a corner trying to get him to admit what he said was bogus. What’s the point besides personal satisfaction? They are not going to pay for it one way or another.

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Important question: Does it hiss only when vehicle is moving?

Replacing the pads and rotors, as well as the other work listed would have no affect on the brake booster. If the hissing is only when the brakes are pressed, that would be the internal seal in the brake booster so it wouldn’t be a hose or anything like that. I could see this being related to the work if the master cylinder was replaced. Otherwise it is just a coincidence (or sabotage).

Does your engine run OK when you step on the brakes or does it stumble? If the brake booster is leaking, that should throw off your air fuel ratio to the engine and cause it to stumble a little.

Question for mechanics here, could the hissing be caused by the ABS module? Maybe the brake fluid was forced backwards from compressing the calipers and the ABS module was damaged?



Looks like you’re right on the edge time wise depending on when the car was first sold, so better hustle on down to the Ford dealer for a look see.

The answer was bogus but the mechanic may have been trying to think of something to appease you when he knew nothing he did could have anything to do with the booster breaking.

The brake bleeding operation (usually required after any big brake job like that) involves work near the brake booster. There’s a thick rubber hose from the intake manifold to the brake booster, perhaps that was already on the verge of cracking and disturbing it did it in. That idea is easy to test. Takes 5 minutes. Ask the shop to test if both the hose and brake booster holds vacuum to 20 inches or not. I expect either one or the other needs to be replaced. That wouldn’t be the shop’s fault imo, just normal wear and tear and the failure was a coincidence or caused by a very slight disturbance which caused an already failing part to completely fail. Not a big deal, just get what’s broken fixed, pay up, then you are safe and your brakes are golden for many miles to come.

The other possibility that comes to mind is if they used the DIY method to bleed the brakes and pushed the pedal to the floor when bleeding. This can easily damage a master cylinder that is fairly old and could stress the booster as well. A good compromise here would be for the OP to pay for parts and the repair shop contributes the labor. At least that’s how I would approach it…

Thanks all for the advice. I was thinking the same split (I pay for parts, they for labor). I’m not trying to get one over on them, the last thing I won’t is someone working for free on something that should be paid for. But I think it’s natural to think they did something that broke or at least aggravated the booster which was fine before and broken at the time I picked the car up. If it matters to them, they need to know that I don’t have faith in them to bring a car to them in the future, particularly if they aren’t willing to admit this is unlikely to be coincidence, at least unlikely enough that any customer would see it as I do.

It’s very likely to be a coincidence. That’s why it’s so stupid that they lied to you. They almost certainly didn’t break it by doing your brake pads. But the fact that they lied to you tells me that they probably did do something dumb that they shouldn’t have been doing and that’s why your booster is damaged.

If I’m innocent and there’s no way that I did the bad thing, I don’t feel the need to lie about what can cause the bad thing.

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Are you referring to the shop’s claim that new brake pads put an extra load on the brake booster? hmmm … I can’t think of any reason for that but maybe there’s a method in the shop’s madness? Anybody here think of a reason a pad job would put an extra load on the brake power booster? Maybe a pad change would cause the power booster to operate in a slightly different range, and that’s the reason the shop said that? It’s a mystery to me why the shop would say that. It would be a good question for Dear Car Talk though.

I think that was answered up in post #14 by @TwinTurbo where he said it is possible if they bled the brakes the DIY way. Maybe the guy didn’t lie but just didn’t know and said something instead of standing there looking stupid.

When the caliper pistons are fully retracted to fit the new pads the first time the brake pedal is pressed the pedal goes to the floor, sometimes twice. That may have torn the already weak booster diaphragm, my source shows a high rate of repairs for this on this vehicle, more that 2,000 reports.

The first stop at a slow speed with new pads can require a great deal of effort with some pads, there have been times that i feared I would drive though the shop door before it opened.

But don’t trust me, I’m a member of the liars club.