Brake Pedal Sinking to floor

[04WHITEEDDIE]

Soft brake pedal sinking to floor on my '04 4x2 EB 4.6L with ~240K miles. I replaced the master cylinder (performed bench bleed before installing MC) and then bled all 4 calipers 2 times with pressure bleeder...nice clear fluid came out with no air bubbles at all calipers....no change to soft pedal. Hooked up the Autel scanner , no ABS codes. I also performed the ABS Auto bleed with the Autel and then bled the calipers again.... no change to soft pedal. I suspect there is internal fluid leak (bypassing) within the ABS hydraulic unit.

Ford no longer offers replacement ABS hydraulic pump for this vehicle. Does anyone know of someone that can repair these ABS hydraulic units? Aftermarket replacement? There is always the salvage yard , but I prefer to rebuild or replace it...I plan to keep driving beyond 300K. Appreciate any advice.

 

[David E]

Hi there, look at the link attached for a place to have it possibly repaired. They will need the part number ready (you can chat for eligibility to repair) and hopefully it will work out.
might be on the expensive price so a salvage yard could still be the option you end up with. If salvage is the case take a bunch just in-case. (that's what I do) Good luck!

Link -- www.ecutesting.com

 

[riphip]

Soft brake pedal sinking to floor on my '04 4x2 EB 4.6L with ~240K miles. I replaced the master cylinder (performed bench bleed before installing MC) and then bled all 4 calipers 2 times with pressure bleeder...nice clear fluid came out with no air bubbles at all calipers....no change to soft pedal. Hooked up the Autel scanner , no ABS codes. I also performed the ABS Auto bleed with the Autel and then bled the calipers again.... no change to soft pedal. I suspect there is internal fluid leak (bypassing) within the ABS hydraulic unit.

Ford no longer offers replacement ABS hydraulic pump for this vehicle. Does anyone know of someone that can repair these ABS hydraulic units? Aftermarket replacement? There is always the salvage yard , but I prefer to rebuild or replace it...I plan to keep driving beyond 300K. Appreciate any advice.

You did not state any testing on vacuum or brake booster. Did you also change booster with MC??

 

[BlackCoffee]

Pedal going all the way to the floor is usually an indication of a bad brake booster. They are not hard to replace, I did one at the beginning of the summer on my 2003 EB with 262K. You won't have to bleed the brakes again, just detach the new master cylinder, replace the booster, and put the cylinder back in place.

 

[04WHITEEDDIE]

Thank you David E...I'll check out Ecutesting.

I also did replace the brake booster (Motorcraft). The pedal is soft with the engine not running , but it gets a lot softer with the engine running from the brake booster assist, which then allows me to push the pedal all the way to the floor. This is interesting, as i thought the pedal is connected to the brake booster via a solid rod which extends outs to the master cylinder? How does brake booster failure allow pedal to go to the floor?

 

[riphip]

Thank you David E...I'll check out Ecutesting.

I also did replace the brake booster (Motorcraft). The pedal is soft with the engine not running , but it gets a lot softer with the engine running from the brake booster assist, which then allows me to push the pedal all the way to the floor. This is interesting, as i thought the pedal is connected to the brake booster via a solid rod which extends outs to the master cylinder? How does brake booster failure allow pedal to go to the floor?

Get a vacuum gauge to make sure you have proper vacuum (if not already performed). Will cause a soft pedal if leaking. Did new booster have a new check valve in it?

 

[USAF Sarge]

Stupid question for you......Does it build up pressure after you pump it a few times?

I had a Jeep that did the same thing, brought it to a shop for them to check, they tired bleeding the brakes, after two bottles of fluid it was still the same, and they gave up and recommended I take it to the dealer.

When I drove it home I had to pump the brakes a few times to build up pressure. Since my wife went into work at 0400-1300 (Light traffic) we traded Jeeps. I had a 2 1/2 drive to work and the beginning of the week and home at the end of the week.

After a few weeks of this process whatever was going on stopped, and it never came back......I assumed there was air trapped in the system somewhere and it finally worked its way out.

So just an ideal.......

 

[BlackCoffee]

I reread and it sounds like you get good brake engagement initially (after the car was running and the booster was working) and then the brake pedal continues to travel to the floor. You suspect a leaking hydraulic valve in the ABS unit. If it were a leaking valve, you would eventually lose pressure to the pads and the brakes would release. If the pedal travel was because you were losing vacuum too quickly in the booster, you would maintain brake pressure and just have the pedal travel to the floor. This is a design feature so lose of vacuum does not cause lose of brakes. If brakes hold, I would concentrate on the booster, and the vacuum lines to the booster.

 

[Trainmaster]

The ECU Testing link is a company in England.

 

[BlackCoffee]

Thank you David E...I'll check out Ecutesting.

I also did replace the brake booster (Motorcraft). The pedal is soft with the engine not running , but it gets a lot softer with the engine running from the brake booster assist, which then allows me to push the pedal all the way to the floor. This is interesting, as i thought the pedal is connected to the brake booster via a solid rod which extends outs to the master cylinder? How does brake booster failure allow pedal to go to the floor?

Since you did replace the brake booster, did you orient the rod correctly. If the booster rod had an offset, it must be orient down. If that is not correct, the booster will not operate correctly. Here is the booster check.