Interesting Ford issue.

[pyrobow]

I am having a brake issue. If I travel anydistance on the highway, my brake warning light will come and the pedal will be hard.
A little more pressure and they will more right.

The hotter it is the more it happens. The brakes are not getting so it appears to be between the booster and petal.

Any heard of anything like this.

[RifleBowPistol]

There is a bit of info you left out of your post. Starters, what is the vehicle, year, engine? Knowing what type of brake system you are dealing with helps a lot.

Then I don't understand these.

1 A little more pressure and they will more right.

2 The brakes are not getting so it appears to be between the booster and petal.

[pyrobow]

Sorry, 2017 F150 3.5 Eco Boost 4x4

[pyrobow]

1. Pressing a little harder and the pressure releases and the brakes work properly.
2. The brakes are not getting hot. That would make me think that the pressure in not in the brake lines.

[RifleBowPistol]

Usually when a brake system that has a vacuum assist brake booster and the pedal is hard. It usually has something to do with the brake booster not working properly. Such as no vacuum in the booster, as a result of a vacuum leak or the engine not creating a vacuum.

Most of the time I have run into a lack of vacuum assist, would be vacuum leak, such as the grommet that the vacuum valve is pushed into, is split. I have seen a few vacuum valves leak. I have seen bad brake boosters.

The fact your brake warning light comes on when this happens would be something new to me. Is it a red warning light or a amber light? Red is usually related to brake fluid pressure problem, or parking brake. Amber lights are usually a result of a ABS related problem.

Either way, I would bet there is some sort of code stored in the system, that would help diagnose the problem.

The symptoms you describe don't sound like anything I have run across in the past. But sounds like it might be a brake booster related problem. If you are getting a amber brake light, you might also have a HCU problem. Which is the hydraulic control unit. It's the component, that has all the valves and motor for the anti lock brakes.

I would not be surprised, if it's not a common problem, well known by Ford dealers. You might try typing in your symptoms into google.

[Boyd1212]

I believe there is a recall on some F-150 with the 3.5 about the master cylinder getting a hole. Might see if your truck is affected.

[pyrobow]

Red light. I have done some reading. Might be a vacuum booster pump.

[Passafist]

I had a 2014 eco boost and there was a recall on the brakes and that is exactly what the brakes would do on mine