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F150 Brake Feels like no brake for a Second

I have a 2001 F150 XLT SuperCab 4x4 with 4 wheel disc brakes. Sometimes when I press the brake pedal, for a second the brakes do not work and then they start to work, the pedal goes down a little bit then start to grab, or when I start braking (braking is working) then for a second it feels like I have no brakes then they start working again. This all in the same push of the pedal, no pumping. It just feels like there is no braking, then it comes back. I can feel the pedal go down, but then the brakes work.

No fluid leaks and I believe the pads are fine.

My question is, is this a problem with the master cylinder or something else I need to look at before replacing the master cylinder?

Is this a common problem on these trucks? This is my first non-GM vehicle ever (been driving for 22 years) and have had the truck for almost 2 years and love it.

Reply to
Lee
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This is a long shot, but I used to have an old BMW with the exact same system. That car had a "hydroboost" type brake booster instead of the vacuum booster most commonly used, and the problem was that the hydraulic accumulator was shot.

nate

Reply to
N8N

I had a similar problem with my Crown Vic. A new booster fixed it right up.

Lugnut

Reply to
lugnut

I had a problem with the MC bypassing. First pedal hit went flat to the floor. Second hit full brakes. It did it twice to me before I went and replaced the MC. I have not heard of it since my 1980 E150 van.

Reply to
Gary Ober

I just wanted to update what I have found so far. Basically I have eliminated the master cylinder and brake booster as the problem. It looks like my ABS was coming on intermittently when the brake is pressed. I disconnected the ABS EBCM so the ABS will not work at all, and my brake issue went away. Now I need to figure out why my ABS would come on intermittently on dry, clear pavement. It is coming on when it should not. I am thinking it may be one of the sensors is bad (I hope because even a rebuilt EBCM is expensive.)

Anyone see either the front or rear sensors go bad to the point where the ABS would activate intermittently when it is not supposed to during braking?

Reply to
Lee

OK...I haven't played/looked at the ABS on my F150, but I had the same problem as you with the ABS on my T-Bird, except that after the first braking and pedal issue, the ABS light would come on detecting a malfunction and deactivate the ABS system. Now in the T-Bird ('93), the setup was a small sensor aimed at basically gear teeth that spun on the hub. The sensor more or less sent info to the computer that determined the speed, and if that wheel was turning based on more or less by how quick the sensors signals were coming back through the gear teeth space as it turned. The computer took the info from all 4 sensors and how much pressure your applying to the brake and made it's calculations. What had apparently happened was that debris or a rock got kicked up into the gear teeth and bent the sensor when it came around so that it wasn't aimed at the gear teeth anymore. All I did was bend it back to where it was supposed to be, by referring to the other sensor on the passenger side and it fixed the problem for $0 and few minutes. I'm sure the truck system is set up different as I'm sure they've improved the ABS system since then (plus I can't imagine that they'd expose the sensors like that of off road vehicles), but I'd pretty much guess it's an issue with one of the sensors.

I'm sorry I can't help too much further other than see what info you can dig up on the sensors....

IYM

"Lee" wrote in message news: snipped-for-privacy@d55g2000hsg.googlegroups.com...

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<IYM>

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