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From day one, my F150 has had a soft brake pedal. You pump it once and it’s solid as a rock! I took it in to my selling dealership and the service manager and I test drove a used 06 on the lot to see if it was just an 06 thing. I was really hoping that this used reference truck didn’t have the same issue as mine. Thankfully it didn’t (have the same soft pedal). The reference truck had a nice solid pedal. David informed me that he would “consult” with the engineers and get back to me. A week later he called and said that the engineers couldn’t really isolate any one component but offered a few suggestions. I dropped off the truck yesterday and they ran a diagnostic on my brake booster. It tested fine. They replaced the master cylinder and adjusted the actuator rod (located between the booster and MC). I picked it up tonight and PRESTO! Brakes feel just as they should. FIRM ON THE FIRST PRESS !!!!!!
I know that there were a few here that have already had the MC replaced and still have the soft pedal. I can say from experience that if the MC and brake booster have already been replaced, it more than likely is the actuator rod. I installed a Wilwood aluminum race MC in my mustang and had to adjust the actuator rod several times before it felt right. Adjust it too far out and the brakes are actually engaged before ever touching the pedal. Adjust it too far in and the pedal feels very soft, like air in the lines. One could easily make this adjustment in their garage, but why bother if it’s under warranty!
Rms8 thanks for the posting it helped resolve my terrible pedal in my 05'
I've read several threads on this subject. I've done the actuator rod adjustment with some improvement. Has anyone ever considered that maybe the V-springs found only on few model years that push the pads away from the rotor could be the cause? It seems to me that every time the brakes are applied, they have to push the pads that entire distance back to the rotor before the brakes once again feel firm. My question is, can these springs be eliminated somehow? Let me know what you think of my theory.
I don't think the those clips are necessary at all. They help retract the pads back post braking for a slight savings of pad wear (and maybe a smidgen of gas).
I know this is an old thread, but this is important info for go_phx and others that have excessive brake pedal travel or a soft brake pedal in their Lincoln Navigator. You have an easier fix than the one listed in this thread. Simply adjust your brake pedal with the pedal adjuster switch so it is about 1 inch up from the furthest down position. Your brakes will be firm and not have as much travel. For some reason if the pedal is adjusted all the way down the brakes are soft and have excessive travel. If, like almost everyone else out there, your brake adjuster only moves the brake pedal about a quarter inch, your adjustment gear is cracked. Simply remove the 3 screws holding the black adjustment gear cover and remove the cover. Then turn the gear by hand so the pedal moves about an inch or more up. To avoid grease on your legs it would be a good idea to reattach the black cover with at least 1 screw. I removed the cable from the cover so if someone inadvertently clicked the pedal adjustment switch it would only move the gas pedal and not change the position for the brake.
Originally Posted by go_phx
So disappointed!!. I have a 2006 Lincoln Navigator that has had the soft brake pedal problem pretty much since I bought it new in March 2007. Like many stories here I have put on three sets of rotors, many new pads and the dealer even replaced the MC after confirming my symptoms earlier this year. When I found this thread last night I was like a kid waiting for XMas morning to try this fix. I am usually on the Expy / Navigator and V8 forums so this thread didn't register until last night when I read something about a brake booster fix - so did a search and here I am.
Anyway... I pulled the MC off this morning and, unfortunately the booster pushrod on my Navigator is a solid rod...no adjusting nut at the end. I pulled and twisted to no avail...no adjustment is available. Buttoned it back up and went for a test drive. Brakes felt a little better / firmer but I'm sure that's just hopeful thinking. We'll see over the course of the next few weeks.
Based on my experience you want anywhere around 0.020" min to 0.040" max clearance from the booster rod to the M/C. A typical paperclip is 0.030", for reference. See pic for visual:
Older generation of Fords had a piece of U-shaped metal that checked the depth of the rod, like this:
NOTE THE ABOVE IS NOT FOR AN F150!!! It is merely for a visual and the depths do not apply to the F150.
You could either use a depth caliper (something not every DIY guy has) or a regular caliper using the pin that protrudes out (see below) into the end of the M/C to compare the depth of the rod, or you could use modeling clay or playdoh on the tip of the booster rod. If the rod pushes all the way through the clay, tolerance is too tight and back the nut down (clockwise). Repeat process until thin layer of clay is present at the tip, about the thickness of a paperclip. I would reiterate the concerns from the experts about just blindly adjusting the nut till just before the brakes drag or by feel. Clearances in hundredths of an inch isn't much, and the lack of fluid recycling isn't noticeable to the driver and you will eventually blow the seals out of the M/C.....likely during a time of intense braking (life/death situation).
My 98 f150 has had spongy brakes for..... 13 years? Been through many mechanics, have replaced fricking everything. Just accepted it... until today... when Mr. State Inspector A-hole FAILED my truck because of the brakes. I told him it was an inherent attribute of a lot of these trucks but he wouldn't listen... So I'm gonna try this tomorrow.
I have noticed that after I tow a trailer for a while my brake pedal will tighten up. I believe that it is due to the rears being used more and readjusting the pads. After a while the pedal will get soft again. Also, how much do you use the e-brake? It is self adjusting but only when it gets used. If you never use it the shoes could be no longer toching the drum and accounting for some of the problem.
The e brake is not self adjusting. Just replaced mine on my 06 due to previous owners lack of maintenance on it, they have no self adjusting capability, one must pull rubber plug to manually adjust star wheel. My actuating linkage and star wheel were rusted solid, and the forward shoe had no lining whatsoever left. Rusted springs all replaced, just removed linkage, hammered apart two halves, freed them up with aerokroil and coated pivot with nickel anti-seize. Adjust after rotor reinstalled, pedal now goes about halfway to floor to hold truck firmly. YouTube has a great video guiding through the whole procedure.
I "strenuously object" to that comment. This is a very advanced mod that should not be performed by just anybody. Putting a sticky on this posting will lead to trouble for lots of people. This point was made somewhere around page 3 by Fireman Dave and I want to revisit it...
These master cylinders are designed to replenish through the center of the pistons. (replenish = fill the brake system to compensate for brake wear, etc). But due to the dynamic lag in the brake system you actually replenish on every release. Then as the pressurized fluid returns from the wheels to the cylinder the fluid needs to escape back into the reservoir. For this purpose, the cylinder was designed with a very small hole in front of the seals - only exposed when the brake pedal is at rest. If you are in manufacturing / engineering, you will understand that there needs to be a tolerance to make sure that hole is open... so you may have to push the brake pedal about 1 mm to get the seal past the small hole.
I like how RMS8 didn't even do this thing that he is telling everyone else to do...
NEWSFLASH - your F150 master cylinder is different than the aftermarket MC you put on your Mustang.
and now to answer a few questions with real information...
Lets start out with the most important point
If RMS8 knew what he was doing, he would tell you that you need to remove the vacuum from the vacuum booster before attempting to remove the cylinder. The easiest way to do this is to pump the brake pedal with the engine off. When the pedal feels hard as a rock, the vacuum is gone and you can remove the MC without any trouble. This will also help to ensure that you do not suck the O-Ring into the booster (it is very difficult to fish it back out)
... lets see... whats worse... having to push the brake pedal an extra mm or sitting on the side of the road with locked brakes...
yes... its a booster output rod
... if the brake feel gets worse, then it is probably due to pad wear and/or moisture in the brake fluid. Brake fluid is Hygroscopic... meaning it absorbs water. Water is much more compressible and therefore can create a "spongy" feeling.
wow... so RMS8 will advise you to pull your MC off the booster, but then advise against bleeding your own brakes. That alone should be evidence that he is clueless.
You are fine in bleeding your own brakes. The only time you need to cycle the ABS is if your brake system is totally dry, or you put on a new ABS module. Granted, bleeding will not change the tiny amount of fluid trapped in the ABS valves, but this is not an issue since it is just a tiny amount of fluid.
So, to sum up my points. I do NOT think that any owner should adjust their own booster output rod. The risk of increased brake wear and even the possibility of sitting on the side of the road waiting for your brakes to cool down and unlock is TOO high.
alright... I'm sure that now RMS8 will bash me like he bashed Fireman Dave. Its amazing how quickly ignorant people attack those with knowledge.
BTW - I am a degreed Mechanical Engineer that designs and tests Master Cylinders for a living. Just thought you might like to know where this information is coming from.
I agree with everything you state- except the water bit. Yes, brake fluid is hygroscopic, however, it is not any more compressible than brake fluid. Water will destroy a braking system internally by rust contamination of ferrous parts(lines,pistons,bores of calipers and wheel cylinders, rubber flex hoses and o rings. It also will boil off when brake temps increase, thereby creating a void in the fluid lines, thus causing a spongy pedal as well. The contaminants also block the supply and return passages over time, restricting fluid travel and braking performance. Just an addendum to your info, wanted to correct and inform the readers of your post.
Anytime my wife drives my truck, which is very rare, the brakes feel really firm afterwards. Two days later and they are back to normal. It's very weird, I don't know what the hell she's doing when she's hitting the brakes.
How attractive is your wife?? Maybe the truck noticed... just sayin.
Based on my experience you want anywhere around 0.020" min to 0.040" max clearance from the booster rod to the M/C.
Nope.
Every brake system I have ever seen is designed such that the booster output rod holds the piston in the proper position by pushing it forward from the resting point of the piston.
If you were to adjust the output rod like you say, then you would hear a click ever time you step on the brakes.
Originally Posted by Mark K
I agree with everything you state- except the water bit. Yes, brake fluid is hygroscopic, however, it is not any more compressible than brake fluid. Water will destroy a braking system internally by rust contamination of ferrous parts(lines,pistons,bores of calipers and wheel cylinders, rubber flex hoses and o rings. It also will boil off when brake temps increase, thereby creating a void in the fluid lines, thus causing a spongy pedal as well.
Actually, brake fluid is approximately 60% less compressible than water. Look up the Bulk Modulus for fluids - larger number means less compressible.
But other than that, I'm happy to know someone agrees with me
I have been having this problem since I replaced the brakes/rotors on my 2011 F-150. I am still under warranty, and have been back to the dealer twice already, trying to resolve. I have an appt today and will mention all of the above to try to get it right. My pedal is very soft and feels like I don't have any braking power. If I hold steady pressure on the pedal, it seems to slowly go right to the floor. I have had the booster pump replaced already under warranty. Maybe they didn't adjust the rod correctly. Thank you for your advice and have a great day.
I have had a 06 F-150 for about a year now. I got it in like new condition as it was a pampered truck. The brakes were replaced after I got it. Properly done, I still never had that tight brake pedal feel. As a kid my family drove several different Ford & Mercury vehicles. My Uncle has owned an F-150 since I can remember. His brake pedal was always tight. My Aunt's old 82 Marquis, same thing. So I am more than excited to find this info!!! I Thank You All for sharing. I may not be " Mr. Goodwrench ", but I am willing to learn & do the work myself. I have learned a lot of valuable info through wise, more educated & experienced people such as yourselves. It has saved me mega bucks, & given me a chance to learn more about the vehicle I drive....Not just its color & how fast it goes! I do love my truck, & I only want to keep it in the shape it should be in. I am heading out to my garage to adjust the rod & see for myself what a difference it can make. Living close to Houston,TX, I need to know that when I hit the brakes that this beast will stop! Thanks again, your info is greatly valued here!!!
10-31-2013, 04:34 PM
. I have a 2006 Lincoln Navigator that has had the soft brake pedal problem pretty much since I bought it new in March 2007. Like many stories here I have put on three sets of rotors, many new pads and the dealer even replaced the MC after confirming my symptoms earlier this year. When I found this thread last night I was like a kid waiting for XMas morning to try this fix. I am usually on the Expy / Navigator and V8 forums so this thread didn't register until last night when I read something about a brake booster fix - so did a search and here I am. 
Thanks
