Hey ya'll, I'm new to the forum and I was working on my 79 f150 4x4 and i rebuilt the rear brakes (new shoes springs adusters, etc.) and I was bleeding my brakes last night hoping that i would get brakes back (they had a blown wheel cylinder and only had full brakes on one wheel) and i bled them out fine, but no real pedal except maybe rock hard after pumping three or four times at the bottom of the pedal travel. same as before, except with my girlfriend in the truck holding the pedal to the ground i could grab the drum and rotate it by hand so im not really sure whats going on there, because the one i did that on is the only one that had full lockup before, the calipers up front look newish, and all hardware in the rear is new, including wheel cylinders, i adjusted the drums and looked all around for leaks, even pulled the master cylinder and didnt find any fluid behind it so its fine, im going to bench bleed it tonight and put it back on, i just bought the truck and am trying to get it safe before snow flies, but i dont have a ton of spare cash to throw around so if anyone has had this problem before any help would be greatly appreciated!

 

How exactly are you bleeding the brakes? Dumb question I know, but have to cover the basics first. How were the streams of fluid?

Any other leaks anywhere else in the lines? Look for damp areas on rubber and hard lines.

How was your brake pedal when you purchased the truck? There but mushy, not there at all, etc.

Is the master/booster new? Sounds to me like the pushrod that goes between the master and the booster is a little bit short.

How does the pedal feel with the engine off versus the engine on? It should be stiff like a rock after 2 pumps with the engine off. Then when you start the truck you should have a firm pedal. Is it soft to the floor in both cases? Lots of variables here.

Final thing, are you sure you have the shoes and hardware back on properly? No insult intended just another base thing to make sure is in order.

 

pump and hold, and the streams werent great, but they werent dribbles either.

no leaks, i climbed around looking for damp spots last night

the brakes werent great when i bought the truck, i drove it back from ohio with full lockout only on the right rear and partial lockout on the left rear, pedal felt same as before, nothing until the bottom ten they firmed up

master looks relatively new (brake lines actually came off) , the short pushrod thing makes since, but if its a stock pushrod why would it be short
you can tell when the power is on, and yea, i finished bleeding and asked my girlfriend how the pedal was and her not being very auto savvy didnt know, i pumped 5-10 times no change in pedal stiffness, but i had clear streams out of all after bleeding
yea, the hardware is on right, i went by the book on it

 

I just went through this in my rig si it's still fresh in my mind. Look up my thread called "brakes are not fun".

The pushrod may be short if it's a new master. It's very common. If the PO replaced the master, then it's actually a good possibility the issue is there. What happens is that each MC is a tiny bit different in exactly how deep their bore goes. So, if the MC is replaced and the new one has a longer, deeper bore, then the rod would be short and not be fully activating the brakes. Follow me so far?

If the pedal goes to the floor with the engine OFF, your booster is shot. No further troubleshooting needed there.

If pedal is firm with engine off but goes to the floor with the engine ON, it may still be the booster's fault (mine was bad and caused this issue). Otherwise there's still air somewhere in there.

Next thing to look at: Do the front brakes work? Jack up the truck, spin the wheel, stomp on the pedal. They should stop.

You should get 2 healthy streams of fluid out your wheel cylinders. Mine blasted fluid back to the U bolts on the axle. If it fizzes or sprays, there's air in there...usually from a pinhole leak or a leaky flange somewhere.

 

I remember posting a link in that thread on how to set the booster output rod length.

That thread located at this link.

https://www.ford-trucks.com/forums/1...e-not-fun.html

 

Thanks for that ultraranger I would've linked to that if I wasn't typing on my
dang phone!

 

last night I pulled the MC to take a look at the pushrod, while the MC was off i benchbled the MC put it back in and all of a sudden i had brakes, the still need a little bleeding, but i spun each wheel and had my cousin hit the brakes and they locked up fine, when I button up a few other things on the truck i will take it out and see how the brakes are, thanks for all the help!

 

Proportioning valve tripped?
EDIT-just saw last post, glad you got it fixed!