1998 Ford F-150 Brake pedal to floor

ROSENFRED

MEMBER
1998 FORD F-150
5.4L
V8
4WD
AUTOMATIC
132,000 MILES

I replace master (bench bled) front calipers and pads, flex hose both sides and rear shoes both sides.
bled all wheels three times and re bled master and re bled all four. Still all the way down when running
have pedal when off not running. Took truck to ford dealer, they bled the ABS and master and all lines again and still no pedal when running. A little help here

5 Replies

HOMER1967

MECHANIC
875 POSTS

Was this low pedal problem the reason you did all the brake work? Was it present before the brake work?I would suggest that you try this, hold you foot on the brake pedal, while doing so start the truck. Does the pedal drop instantly?Next I would suggest that you make sure that the bleeder screws on each front caliper are on the top, these calipers can be mistakeingly installed on the wrong side with the bleeders on the bottom, and to purge air the bleeders must be on top, second clamp off the vacuum line going to the brake booster and see if that changes anything. Thirdly. Is this vehicle rear wheel or four wheel anti-lock brakes?Also hcu (hydraulic control unit) failure is very common on these trucks. Let me know the results of these few tests and I will try to help you to proceed.

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Saturday, January 10th, 2015 AT 5:23 PM

ROSENFRED

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2 POSTS

Got truck a few month ago, had to do a head job to it, The brake b4 I replace
everything were low to the floor, I knew it needed brake when I look at the front pads and started there and on to the rear which was worst than the front, just shoes and wheel cylinders for rear and that when pedal went to the floor, mechanic said master was bad and replace it (bench bled) and bled when hook up lines, The breeder screws are on the top. Held pedal and when started drop instantly. Clamp hose at booster with engine running
and had good pedal. This is a 4wd with drums at the rear, no abs there that
i can tell. Now what is this HCU you are talking about and where is it?
Thanks, waiting to hear

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Saturday, January 10th, 2015 AT 6:30 PM

HOMER1967

MECHANIC
875 POSTS

Good work, the hcu is just the older version of an abs module. Is there sensor in the middle of the rear on the top, with a plug going to it? Also pedal hard with vacuum line clamped off and truck running? Is that correct? If so then you have a bad brake booster my friend.

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Saturday, January 10th, 2015 AT 6:49 PM

ROSENFRED

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2 POSTS

Finally Got the Brake booster change, but ran into more problems, but now the engine runs and the brake pedal still goes to the floor with the new
booster install. Is there something I missed

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Wednesday, January 14th, 2015 AT 12:44 PM

HOMER1967

MECHANIC
875 POSTS

Wow. The sypmtoms definatley indicated a bad booster, but you may have an underlying hcu issue. To diagnose that you need to take specific pressure measurements and perform specific tests. Sometimes the hcu can be really hard to bleed and may require a scan tool to bleed. If you have enough of a brake pedal to safely do this you could try to lock up your brakes on a loose gravel road on in the dirt, nail the pedal and try to get the abs motor to engage. You'll know if it does because you will feel it in the pedal and you may even hear it. If you can not do that safely, do you know someone with a scan tool that could try to bleed them for you that way? And if you do get them to lock up and feel the pump kick in, then bleed them again manually. Let me know.