I have an '07 f150, 4x4. I did some brake work in preparation of selling the truck and now I have no brakes. I bled the brake lines until I was 100% sure there was no more air in the lines. Everything seemed fine until I started it up; the brake pedal went straight to the floor. I went down to the local dealership and talked to them about it. Afterwards, I re-bled the brakes with ignition turn to the 'Accessory' position so that the electronic brake booster was on. I then bled the brakes starting with passenger rear side, then the driver rear, then the passenger front and lastly, the driver front side. Pressure built up and they felt fine. Again, I took the truck off the jacks, started it up and tried to drive it to test it out; the brake pedal went straight to the floor again.

They feel better than they did the first time I bled them, but still nowhere near what they felt like before I took them apart. I double checked everything and found no signs of leaking or anything.

Any suggestions? Thanks in advance.

 

first suggestion is to take it to someone that knows what they are doing.
(no offense)

You don't have an "electronic brake booster"... you have a vacuum booster. You have to have the engine running to maintain boost over multiple brake applies.

That is the reason the pedal feels good till you take it off the jacks and start the engine. No boost = hard pedal.

As for why you have such a bad bleed... the only logical answer is that you are improperly bleeding. I'm assuming you don't have a brake line leaking (it would be very rare on a 2007).

If you think the third time will be better, then be sure to search on here to learn the proper bleeding procedure before trying again.

 

what kind of brake work, more explination is needed. just pads, calipers, what did you change/repair on the system?

 

I did a custom cross drill on my rotors and painted my brake calipers. And no offense taken; I have bled MANY, MANY, MANY brake systems before. Apparently my assistant wasn't as knowledgeable as I thought before we started this lil project. There are no leaks, at all... Anywhere.

I didn't know that it was a 'vacuum booster'. I am not familiar with that particular part. And why does the engine actually have to be running? I would presume that anything electronically operated will function normally with the ignition in the 'accessory' position, if it is normally running while the engine is running (i.e. ABS). I know this may seem a bit stupid to ask, but does the vacuum pump run off the engine? Like I said, I am not familiar with this particular part and am not sure if it is belt driven, vacuum operated similarly to intake manifold vacuum or what exactly.

The procedure I am using is starting with the truck jacked up to a level position, take the cap off the master cylinder resevour and then have an assistant start pumping. Crack the passenger side rear bleeder valve, close it, then have my helper start pumping again. I repeated this process until solid fluid was coming out and went in order from passenger side rear, to driver side rear, to passenger side front, to drive side front. I repeated this process a few times and have tried with ignition in every position, except with the engine actually. running. I have not tried that yet.

Any other suggestions or idears? I am particularly interested in more on the vacuum booster and/or the ABS pump. I am curious how these parts might effect the bleeding process and the pedal pressure. I am also curious about what position the ignition needs to be in and whether or not the engine actually has to be running. Thanks again in advance.

 

An engine that isn't running can't build any vacuum, so.....

 

Does the pedal harden after pumping them? Seems like a common thing after a brake job to seat the pads for the first time?!?

 

did you remove the calipers from the truck? if so (no offense ment) did you put them back on the correct side? Bleeders on the top of the caliper? Make sure the MC was filled after each bleed to ensure no air was let in? the booster makes vaccum off the motor to assist the MC during braking, should have no bering on the bleeding of the system. key off, pump the brake 4 to 5 times, bleed as you discribed farthest away first. hold it, bleed, tighten, repeat about 4 times. Only thing I've seen like this is the proportioning valve sticking. Only way to correct without a power bleeder or replacing it is to open all the bleeders have someone mash the brake pedal down all the way and hold it, then go arround and tighten all the bleeders. This centers the valve and blows out any stuck air. then use the normal bleed process discribed above.

 

I removed the brake calipers completely from the truck. Took the mounting bolts out of the mounting bracket and disconnected the brake line. Yes, I definitely took the calipers off. Lol. And I have read in a couple different places about people putting them on backwards. I am 100% sure that I put them back on the way they came off. I would presume that since I originally bought the truck from a dealership and the calipers have never been removed up to this point and I put them on exactly the way they came off, they are on correcty. I suppose it it is possible for them be on backwards, I'll double check. But I can tell you that the bleeder valves arent on top. They are more so towards the bottom; just below the banjo bolt for the brake line connection.

I am not sure of your trying to imply that I changed the pads, but I didnt. They still have PLENTY of life left on them. But nonetheless; the pedal does stiffen up after pumping it several times. And it holds pressure, for a few seconds. But regardless of which position the ignition is in, I pump it a few times, get the pressure built up (even after just cracking/closing a bleeder valve) and then leave it be a few seconds; the pedal goes more less straight to the floor. It almost instantly gets spongy again and then looses all pressure after a few seconds.

Keep the ideas flowing if at all possible. This is helping me out figure this. Thanks a bunch y'all.

 

Most vehicles get the vacuum from the engine. So the vacuum booster is "powered" by engine vacuum. There is no electronic component (like a pump) to be powered by the key.

Some newer vehicles can't supply sufficient vacuum levels, so they use a vacuum pump. It can either be electronic or belt driven.

The booster game is changing... with new engines that shut off when you sit still, hybrids, electrics, diesels, etc... there is a lack of vacuum supply. We will soon be seeing new styles of electronic or hydraulic boosters in the passenger car / light truck market.

But for now, your F150 uses a vacuum booster that gets vacuum from the engine.


As for your calipers - sounds like they are backwards... the bleed screw must be on top.
check out the second picture here, it shows this clearly
http://www.happywrenching.com/ford/f...placement.html

 

Thanks for that pic link. That's interesting cause I dont believe my bleed valves were ever on the top side. I'll switch'em and see what happens.

And it shouldn't matter if the ignition is on/off or what position the key is in; no key required, right?

 

Not implying that you changed the pads... but your comment "I'll double check. But I can tell you that the bleeder valves arent on top. They are more so towards the bottom; just below the banjo bolt for the brake line connection".....

The bleeders should be above the bolt that holds the brake line otherwise you'll never get all the air out and this problem will never go away. if they're in that position you have them on the wrong side. Here's what it should look like, this is a pic of the drivers side front
.

 

Correct "No key required"

 

what kind of brake work, more explination is needed.

 

The engine should be idling when you bleed your brakes. This ensures a constant supply of vacuum to the vacuum booster and makes it easier to bleed.

You can of course leave the engine off, but then you will have to be pushing on the brake pedal much harder to get the fluid to push out the bleed screw. I'd be concerned that you might not be getting full pedal travel during your bleed. (unless you are a large guy with strong legs)

FWIW - when I bleed my brakes I have the engine idling.

 

Sorry for taking a few days to get back to y'all (I have LAZY assistants, lol). Anywho, I looked at my calipers and they were in fact on backwards. Those pic links and posted the one posted pic helped out a lot; Thanks guys.

Further more, I bled the hell out of the system once I swapped the calipers. I bought new fluid and only put new, out-of-the-bottle fluid into the reservoir. I went through the bleeding sequence twice and cracked each bleeder valve probably 7, maybe 8 times. I was getting nothing but new fluid with not bubbles out of all 4 calipers.

The brakes felt fine, then I started it up and they went to the floor, mush. I still attempted to drive it and didn't even get out of my drive way. They worked better, but still not anywhere near what they were before I took everything apart. The only thing I can think of is to bleed them, yet again, with engine idling.

And as a general precaution, I double checked all the lines and fittings, everything was solid. No leaks or anything dripping. I'm getting more and more puzzled.

The other possibility that I came up with is perhaps air bubbles did actually get all the way up into the ABS pump. I'm not sure how likely that is though. Common? Rare? Ideas? Thanks again.