Weird brake problem

[Cadburysx5]

Another thing that can cause that is a bad wheel bearing or failing one since the wheel will flex as u hit the brakes.

[admranger]

I'm starting to have this too... Brake works fine and then at the end of a long-ish stop, the pedal pushes back on my foot and braking force seems to lighten up. I can stop, but the forces my leg has to exert on the brake pedal are very, very large.

So is that the pump or the booster?

Oh yeah, just remembered that when I started the car before this issue arose, there was a suction sound that emanated from the engine compartment. It was short lived and had a wheezing sound to it. Hmmm....

[Junkycosmos]

hi adminranger
When my booster was leaking I could hear a faint almost toilet running sound when holding foot on brakes at idle. After replace the faint sound is gone.

Other good test of booster vs master is do the brakes work 100% as expected with engine off after 2nd/3rd press? Point is booster only "regenerates" when engine is on. Careful how you test this since the X is a beast so manual braking is a heavy hard step on pedal, few guys suggested parked on a slope. If all is "normal" and consistent here then your master is likely fine.

[admranger]

It's not the master, I know what that feels like (had to replace the one on the race car).

So it's either the vacuum pump or the booster. I'm going to order up the vacuum pump o-rings. I put my hand under the pump this morning and it is caked with black crud. I'm guessing there's a leak that needs fixing if nothing else...

[stiubhartach]

I also noticed this problem today out of the blue. Pedal force is normal until the end of a long stop, then requires stamping on the pedal hard to finish the stop.

Any new developments or notes on the final solutions?

[Fifty150hs]

Originally Posted by stiubhartach

I also noticed this problem today out of the blue. Pedal force is normal until the end of a long stop, then requires stamping on the pedal hard to finish the stop.

Any new developments or notes on the final solutions?

Sounds like classic brake fade.

[Hazeeo]

I have just found this and wanted to find out what the problem was as I think I have the same problem.
From take off out of garage I don't have brakes, feels like I'm pressing down on an inflating balloon but when I'm driving the brake feels normal, although when stopped at traffic lights I feel the pressure building up and the brake pedal getting higher and grip failing.. any ideas?

[indian farmer]

I have this problem too. braking at high speed is fine but if the brakes are feathered the assistance becomes less and effort is required to depress the pedal. in traffic I have to use the auto hold otherwise it starts to creep.
I have changed the seal on the vacuum pump and it has improved the braking but not cured the problem.

the vacuum is at 29in at idle where as it was at 14in before

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I have replaced the Brake Booster and it is all good

on opening up the old booster there was oil in it.

if you have a similar problem I would check the vacuum and if its above the 20in at idle then the problem is in the booster.