mercrecon117

I have a 2011 F-150 Lariat Supercrew 4x4 with the 6.2L. The issue that I am having is with the brakes. When the engine is running the pedal sinks to the floor with very little pressure. When driving there is little to no braking force. After applying the pedal and it sinks to the floor it takes about ten seconds to stop the vehicle at low speeds (10-15 mph). If I pump the pedal before stopping, the pedal is a small bit more reactive. I have replaced the pads, front calipers, the check valve on the break booster, and the master cylinder. when I initially replaced the pads I noticed that there was an issue with the front driver side caliper not releasing. I went to replace the calipers and noticed that the driver side front brake line was not leaking as much as the other one, so I replaced that brake line. I have bled the brake lines so many times that the fluid has been completely replaced. When bleeding the brakes I would pump and it would get hard like it should. If I pump the brakes and start the engine the pedal sinks to the floor. The truck doesn't have any leaks, brake lines included. There are no warning lights on the dash. I purchased a power brake booster from a Ford dealer today and I have had second thoughts about installing it. Any help would be greatly appreciated.

Scarlet

As I recall, there was a TSB on brake problems on a few models? But I think that was on some Ecoboost trucks. I forget where I read it, but it was either on these forums or at f150online. I recall something about the brake pedal pressure dropping. And about a few people who had problems in reverse saying the truck wouldn't stop. Don't have much more than that. I would check TSB's, maybe a Google search?

mercrecon117

Thanks for the response Scarlet,
There was an issue with the Eco Boost's brake system that resulted from a failing/failed vacuum pump. I checked the TSB's and I don't see anything relating to my issue. I've done an exhaustive study of google, along with a buddy that has been helping me out, all to no avail.
I had found a video on YouTube where a guy had the exact same problem on an older expedition and he replace the ABS module and it fixed the issue. I found a used ABS module and swapped it out today and I am now getting four different codes. The dash lights up the ABS, Parking Brake light, and traction control. I get other warning messages as well. I think I might be !

Merc

Spiky

Do you need some sort of reprogram for ABS?

joedotmac

If it were mine I would invest a little cash into diagnostics before blindly replacing parts. Been there done that. Still haven't learned my lesson.

There are a host of vacuum readings and testing processes that can corroborate or clear the booster from being an issue.

1. Disconnect the brake booster vacuum sensor check valve from the brake booster and connect a vacuum tester to the booster side of the vacuum check valve.

2. Apply the parking brake. Start the engine and put in neutral with chalks around wheels to keep truck from moving.

3. Verify the vacuum reading at the check valve with the engine running at idle.
* Subtract 1Hg for every 1000 feet of elevation of your location
*Reading should be in nominal range of 15 to 22 HG

4A. If vacuum is in range. Stop engine. Reconnect the vacuum sensor check valve. Push the brake pedal down several times to exhaust any stored vacuum. Push the brake pedal down and hold. Start the engine. If the pedal moves downward after engine start the booster is operating as designed. If the pedal doesn't move install new booster.

4B. From step 3.

If the vacuum isn't in range. With engine running at idle. Disconnect the vacuum sensor check valve from the hose. Using the vacuum gauge directly on the hose measure that vacuum is in range. If vacuum is in range stop engine and replace the sensor check valve.

If vacuum is not in range with engine idle and measuring vacuum direct from hose, stop the engine. Reconnect the vacuum sensor check valve to vacuum hose.

Troubleshooting further gets long as there are tests for vehicles with and without a brake vacuum pump. I'm not certain how brake booster vacuum is generated in the 6.2. I believe its simply generated from siphoning off intake vacuum, but not certain.