Hard brake pedal replaced the break booster, master cylinder?

2007 FORD F-150
300,000 MILES • 5.4L • AUTOMATIC
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Not sure how to proceed,I have checked and replaced the break booster, master cylinder, and abs pump and module.intial issue was a hard break pedal, after checking the booster, I found a broken Port on the passenger side of the upper intake. I replaced the intake, and checked vacuum, which was at 30 hg.replaced the booster check valve and booster which was full of break fluid. Replaced the master cylinder, which was leaking into the break booster.i also changed the abs pump and module with a good used unit. I bled the system multiple times, but I still have a pedal that is rock hard. I'm not sure what else to check everything else seems to check out. Also bench bled the master cylinder. Please advise what else should I check.
May 10, 2026 at 2:27 PM
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What to check next

Diagnostic guidance. Suggested checks and possible repairs are separate from the owner's reported results.

Keep the truck out of road service and arrange professional brake diagnosis. Have the technician verify correct parts and installation, then evaluate brake assistance and hydraulic operation with the matching service procedures. Retained vacuum alone does not demonstrate adequate booster assistance. Do not treat the thread's line-loosening suggestion as a definitive ABS diagnosis or a home repair procedure. Further testing should identify the fault before another major component is purchased.

Guidance references and applicability

Source discussion: question 1712732 https://2carpros.com/questions/hard-brake-pedal-72999998--1712732 Supports the reported history and outcome only. Follow-up guidance is editorial synthesis; unverified specifications and diagnoses are not adopted. HELLA: Checking the brakes https://www.hella.com/techworld/uk/technical/brakes/checking-the-brakes/ General brake-inspection background. Not a vehicle-specific booster, ABS, bleeding or adjustment procedure; it does not establish the cause in this discussion.

Read the replies · Discussion summary and reported outcome

AI-ASSISTED GUIDANCE · REVIEWED BY 2CARPROS
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STRAILER
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You may have a defective booster, start the engine and then shut it off. Next, pop the check valve out of the booster and see if you hear vacuum escaping. If so the boost is good, if not the boost is defective, if that checks out lets raise the front of the truck and spin the front tires to make sure they are not locked up, if so then the push rod in the booster is adjusted to far out are the brake master is defective. Please go over this guide as well.

https://www.2carpros.com/articles/a-comprehensive-guide-to-fixing-automotive-brakes-locking-up/

Please upload a short video in your response of the problem, so I can see what's going on
May 11, 2026 at 10:15 AM
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Thank you for your response, I was not able to get a video yet but, a friend tried replacing the brake booster with another new booster with the same results.This truck does have the adjustable pedals, but we have moved them in both directions with no effect to the pedal feel.the front wheels spin freely, we had to bleed the system initially after replacing the master cylinder, which was defective, and leaking. I will try and get a short video next time to better illustrate what's happening.
May 15, 2026 at 5:01 AM
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STRAILER
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So the adjustable pedal truck might have a different booster then the non adjustable type so make sure you are getting the correct booster, also let check the rear tires to make sure then spin as well. Did you get a chance to remove the check valve of the booster to see if vacuum escaped? It could be vacuum is not getting to the booster or the booster is leaking so the check valve removal test will tell us that, engine off there should be vacuum inside the booster.
May 15, 2026 at 8:10 AM
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Yes the check valve has been checked and replaced, we have lot driven the truck to try and get a feel for the stopping ability, but the pedal is way to stiff. We have to almost stand on the break pedal to get the truck to stop. The rear wheels spin freely also. The check valve when pulled did release vacuum which at this point really has me stomped?
May 15, 2026 at 8:45 AM
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STRAILER
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I would loosen the lines at the ABS unit and then press the brake pedal to see if it moves freely, (parking brake on) if the pedal moves the used ABS unit is bad. Did you have this problem before you replaced the parts? Also, it is rare but I have seen the brake flex hoses fall apart internally and act like a one way valve stopping the flow of brake fluid.
May 15, 2026 at 9:01 AM
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Yes the problem was the initial reason for changing the booster and master cylinder, which both were bad. The abs pump and module were charged after everything else. At first it wasn't activating, now with the used unit it seems to work.i will double check it at this point.
May 15, 2026 at 10:31 AM
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STRAILER
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Yep, we need to find out if this is a mechanical issue or a hydraulic problem. This is why I wanted you to loosen the lines to see if the brake pedal pushes down easily.
May 16, 2026 at 10:39 AM

Discussion summary

Hard brake pedal replaced the break booster, master cylinder?

The owner reported a persistently hard brake pedal despite intake, booster, master-cylinder and used ABS-unit replacements. The original master cylinder reportedly leaked into the booster. A second replacement booster did not resolve the symptom; the owner reported freely turning wheels and retained vacuum but still needed excessive pedal effort.

Reported outcome: The excessive pedal effort remained unresolved at the end of the discussion.

The reported vacuum reading, replacement-part compatibility and used ABS-unit condition were not independently verified. Several proposed causes remained untested.

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AI-ASSISTED SUMMARY · REVIEWED BY 2CARPROS
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