Do you have to bleed the brakes when done? Mine are a tad mushy

 

That procedure will not allow air in the system so it does not cause the need for bleeding. However, that does not mean you haven't gotten air in the lines some other way. Bleed them and see if the mushyness goes away, if not, then I would suspect the master cylinder

 

thanks - i had to replace my master cylinder because everything else checked good and i had a mushy pedal and on 2 ocations the pedal want to the floor and had no braking effect- yes i flew into traffic pounding on the horn.... luckily, i did not hit anything.

 

hmm, wouldn't removing the master cylinder cause you to have to bleed the system as you put air into the line, or does that shaft push on the enclosed piston?

 

Once again I will add my warning to this topic. Please read this and consider these facts before performing this modification.

What these people are doing is removing the dead stroke from the master cylinder (the stroke that is required to build pressure). The dead stroke is there for a couple reasons... and yes, one of them is manufacturing tolerances. But the other reason is to ensure that the seals are far enough behind the hole into the reservoir that the fluid can move back and forth. Once you advance the pistons by adjusting the booster output rod you could push the seals past the small hole that allows the fluid to flow back to the booster you could trap pressure in your brake system and drag your brakes.

You might notice this right away and fix it. But you might not notice it right away... it might only happen in extraordinary circumstances. Two very specific examples:
(1) you have a new truck with stability control (ESP). The ESP senses you losing traction and pumps fluid from the MC to apply your brakes. At the same time, you hit your brake pedal. Now the system is "super-charged" with more brake fluid than it can hold when not under pressure. You remove your foot from the pedal, but you adjusted your booster output rod so your seals are still covering the hole to your reservoir. You will now find yourself sitting on the side of the road till someone takes a wrench and opens up one of your brake fittings to release the pressure.
(2) you are on vacation, driving through the mountains. You are driving down the mountain and using your brakes fairly heavily. While on your brakes, your calipers get hot... really hot... and the brake fluid gets hot, and expands. You get to the bottom of the hill and remove your foot from the pedal. Again, too much fluid in the system and your seals are blocking the holes. The only good news is that once your brakes cool down you can drive away...

For what its worth... I design, build, and test these master cylinders. I have not performed this modification on my truck.

... still don't believe me... here is an independent verification
https://www.f150online.com/forums/4710908-post2.html

 

I just installed new brake pads and rotors on the front of my '07 F150. I had a pulsing feel during heavy braking so I figured the rotors were warped. I guess they were as the new rotors stop really well. It seems now I have a soft brake pedal. I drove it and it stops really good and doens't seem to have any issues, but I like a much harder pedal. It was soft before the new pads, but not this soft. Sitting in the driveway in park, I can usually push the pedal to the floor. When driving it stops really good. I think the master cylinder in these trucks is the trouble, or a soft brake line as mentioned in another post. The fluid in my truck is very clean and there is no way it should need to be bled. The pedal shaft adjustment this thread is about seems like a 'band-aid', I think there are underlying problems. Any ideas?

 

any ideas?
Yes - I think it is performing as designed.

It is the booster tuning profile, along with the master cylinder bore size, that determines the way the brake pedal feels. Ford just picked a different tuning profile than you may see in other cars.

Typically Ford/Chrysler/GM tend to have a "softer" feel to the brake pedal. This is nice as it allows you to easily modulate how much stopping force you use.

JOEMs (Nissan, Toyota, etc) tend to have a "harder" feel to their brake pedals. I've driven some cars where you barely touch the brake pedal and it feels like you stomped on the F150 brake pedal. This is because the JOEMs like a higher jump-in on their boosters.

Personally, I like my F150 better than these other cars. I have total control over braking force. Yes, to slam on the brakes you have to push the pedal further... but I'm OK with that. It is much better than the alternative where a fly landing on your brake pedal throws you into your seatbelt.

 

Great write up!

I've had the soft/not firm pedal for many years, even after complete brake rebuild and bleed. When new it was soft but firm which was great. I was debating replacing the master cylinder and/or booster since with 206k it wouldn't hurt.

I think I'll try this adjustment first just for kicks. My ABS light is intermittent with no apparent cause, all brakes look fine and can't see anything wrong. Since ABS on my truck sucks anyway, I'm not to concerned, but looking for answers to make sure I have the complete picture.

I'm wondering if this adjustment will solve the ABS light problem? I guess I'll find out.

 

I just bought a nice 97' about 6 days ago and had this problem along with the need to replace my rear brake cables. They were rusted up, seized up and were locked in a position near enough to being fully engaged to cause the rear tires to lock up when I lightly pressed the brake pedal. That problem was fixed by replacing them. As for this problem in this post, well I had this experience and all the others mentioned as well and couldn't put my finger on the problem until you sent this out to us. I changed all the brakes, hardware and hoses all the way around. I found that the previous owner had changed the vacuum booster but failed to adjust it apparently. It took me about 6 full turns to get it to where I was content with no brake drag or anything. I also had to hook up my boat trailer and test it out with the new adjustments and everything worked great. Thanks for the post, pictures and input. Since I can't email a beer, I'll have about 6 in honor of you. The other 6 are like potato chips...one just isn't enough.

 

If you have a rear abs system and its similar to the rear abs on my 96 ram, the rear brakes are not adjusting properly due to the brake cables needing replacement/ adjustment. This can cause the rears not to engage properly and in turn cause the ABS light to pop on. If the rear brakes don't get adjusted but wear down to the point that they don't contact the drum with enough force, then the abs system will think it's a malfunction and throw the light on as well as a code. The parking/ emergency brake is what adjusts the rear brakes each time press it down. I've heard many times about driving in reverse and applying the brake to adjust it but it's faster to use your e-brake to do this. It also keeps it in working condition for that time when you may need it. When you apply the e-brake you may notice a clicking sound from the rear end. That's the adjuster in the rear brakes. (drums only). I would look into seeing what the ABS codes say first because it could be something serious. If there's nothing serious then look at your rear brake cables for adjusting or replacing. Worked for me on my 96 Ram and 97 F150.

 

If you have a rear abs system and its similar to the rear abs on my 96 ram, the rear brakes are not adjusting properly due to the brake cables needing replacement/ adjustment. This can cause the rears not to engage properly and in turn cause the ABS light to pop on. If the rear brakes don't get adjusted but wear down to the point that they don't contact the drum with enough force, then the abs system will think it's a malfunction and throw the light on as well as a code. The parking/ emergency brake is what adjusts the rear brakes each time press it down. I've heard many times about driving in reverse and applying the brake to adjust it but it's faster to use your e-brake to do this. It also keeps it in working condition for that time when you may need it. When you apply the e-brake you may notice a clicking sound from the rear end. That's the adjuster in the rear brakes. (drums only). I would look into seeing what the ABS codes say first because it could be something serious. If there's nothing serious then look at your rear brake cables for adjusting or replacing. Worked for me on my 96 Ram and 97 F150.

 

Will this adjustment raise the brake pedal height? I just installed a new power brake booster in my daughter's 2004 Escape. During the Polar Vortex temps we've been having in KC her first braking attempt in the morning was like trying to stop Fred Flintstone's car. I replaced the check valve on the booster first, but the problem persisted.

After putting on the new booster, the brake pedal is 1/4" short of reaching plunger on the stop light switch. There is no way to adjust the bracket on which the switch is mounted.

I don't want to start adjusting on the plunger like shown in the photos if it is not going to help the brake pedal height. And thinking about it, would I really need to go the opposite direction of adjustment to RAISE the brake pedal but move the plunger BACK a bit. The instruction sheet that came with the reman Cardone booster has no instruction for brake pedal adjustment.

If the adjustment DOES affect brake pedal height, I am thinking I should see that even before reattaching the master cylinder, correct?

 

First off - if the engine is running, then a check valve won't cause a hard pedal. (if the engine is off, then yes, a bad check valve will cause the vacuum to leak out quickly and the pedal will be hard).

So more likely, you have a vacuum leak inside the booster (they are worse at cold temps) so that is why the pedal was so hard. You were basically trying to stop with no brake boost (or very little boost).

Secondly - no, changing the output rod will not move the input rod (which is attached to the brake pedal).

For your problem - are you saying the brake light is always on? Or it won't come on? Try taking a picture of the switch area.

The fix must be in the alignment of the stop light switch. Look closer for adjustments to it. Or did you bump it during the swap and bend something?

 

I spoke with one of the techs at Cardone, who made the reman brake booster. He suggested I exchange it but the pedal rod on the exchanged unit was exactly the same length. This left the brake pedal still shy of the stop light switch by about 1/4". Since there was no adjustment in the switch, nor the bracket, I ended up bracing my shoulder against the front of the driver's seat and PUSHING the bracket with all my might to bend it forward. There appeared to be an adjustment bolt at the top of the dashboard frame, but spot welds on either side of the bolt kept it from moving when I had loosened it. Bending the bracket seemed to be the only solution.

 

ya, I still don't understand what you mean by "shy of the stop light switch by about 1/4"

Is this a side-to-side alignment issue? Or a front-to-back issue?

What exactly did you bend?

Do you have any pictures?

Is it working now?