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.

 

[GAINMOB]

my local repair shop replaced my ABS pump and as far as i know they got the part aftermarket

 

[04WHITEEDDIE]

I checked the vacuum hose at the check valve ...getting ~20 in Hg at idle. The check valve is new (came with the new brake booster.) Just to be sure ,I pulled it out and checked it ...only draws air 1 way...seems to be working fine.

Without the engine running, brake pedal has some firmness but sinks slowly with firm foot pressure. As soon as i start the engine, the pedal goes right the floor without much foot pressure. After the turn engine off, I can depress the pedal to the floor easily 1 time and then it starts to firm up .

My brake booster rod does'nt have the "offset" where it connect to the pedal.

 

[04WHITEEDDIE]

Gain-Mod...I searched the internet , I cant find anyone that sells new ABS pump (OEM or aftermarket)..seems to be a discontinued part. Original part was manufactured by Ate .When did you get yours replaced?

 

[BlackCoffee]

It's time to find a reliable junk yard that will let you pull parts. The good news is that when you pull it yourself, they usually only charge 15-25 bucks depending on the part.

 

[Tocapet]

I had a brake booster go bad in a '73 Jeep Wagoneer that I had. It was leaking vacuum. Stepping on the brake pedal caused the engine to stumble & run rough at a stoplight. Couldn't find a replacement anywhere, so I just took the booster off and mounted the master cylinder right on the firewall. This gave me standard non-power brakes. Drove it like that, passed inspection like that & sold it like that. Sorry to be off-topic here, but on some vehicles that can be an option.

 

[juan214]

Might be late or if it still persist. I had the same issue on my 99. Take a look at the rear brake line. Specifically the one on the frame rail above the rear end. I had a tiny pin hole in it. It never leaked onto the ground because of the location of the leak. The front brakes / line held the pressure and slowly drop until the front brakes slowed and stopped the truck. I only do city driving around town as of late. I basically ignored it.

How did i figure I had no rear brakes? Yearly Safety inspection Parking Brake check and adjustments. While in the air and after adjustment applied the brakes and the rears kept spinning.

 

[Drae]

Old hydraulic brake hoses can cause a soft pedal too. If you haven't replaced those, it's worth a shot. I have an 03 too and it's about time for me to change mines. A little mushy also.

 

[04WHITEEDDIE]

Thanks , I was thinking about the hoses too...16 years old...it maybe time.

 

[riphip]

Rockauto.com is where I bought mine. Went ahead and replaced them all. Like you, 16 years old