Ok guys so we have a 89 F250 4x4 XL 351W ZF5 with the 3" rear brakes. I just put new shoes, wheel cylinders, pads, and calipers on the truck as the trucks braking couldn't stop a Prius. So when we put it back together (and bled the system 5 times with no air coming out) we tried driving the truck and the braking you had to pump while the truck was on to get it to even slow down. So I figured the Master was bad. Went to the junkyard picked up a master and Vacuum booster and threw it on yesterday (haven't bled the lines yet) and I started the truck up backed up and the brakes were stronger but still not the best. Also after putting the master and vacuum booster on we noticed a slight hissing noise and the dash light for the parking brake came on but the parking brake is off (checked multiple times) and the switch is good.
By the way when I removed the vacuum line (big hose from the intake) to the vacuum booster their was a big gush of air sound (from our truck).
So do you all think I have a bad vacuum booster or just need to bleed the lines?
By the way I had put a new ABS sensor in the rear end and it broke inside the rear end so I replaced it with the old one but there was no light after replacing it so I don't think it is that but hey I could be wrong.
Trav

 

Did you adjust the rear shoes properly? Is the pedal spongy/does it go to the floor? Or is it hard to push?

 

When the truck is off it is hard and feels good but when you start the truck and press the brake it is spongy and goes about 3/4s of the way to the floor then feels stronger then the other booster and master plus after replacing the booster it would go up so far then we press the acc. and the pedal goes up a bit.

I thought the rear shoes were self adjusting?
How do I adjust the rear shoes till they are right? (I know about the wheel but how far?)


I had an 86 F150 that would make a hissing sound ended up being the brake booster and master so I replaced them truck never hissed again but on this 89 both of those parts (from junkyard and one on it originally) have hissed a bit.
Trav

 

Sorry for a double post but do I have to run the engine for a while to build up vacuum pressure? I didn't read anything about that in my chiltion book but so far this Chiltion book has been wrong a couple of times.
Trav

 

A new one is 35 bucks why anyone would screw around with a junkyard MC is beyond me, you already had one of those to start with.

Anyway, if the master cylinder ran dry at any point even for a moment you're gonna have to bleed it first, bench bleed it first then connect the lines bleeding them.

Then work farthest to nearest and don't forget the antilock valve, if it hasn't been bypassed/eliminated yet that is.

And yea sounds like you bought a junk booster based on what you stated, put the one you had back on.

Do not use full length strokes of the piston while BBing the master cylinder, doing so to one will kill it. Short strokes until piston no longer moves 1/16 to 1/8th inch and is solid, at that point you can put it on the truck connect and bleed lines. Doing so before achieve that is a waste of time.

 

Well I tried that and no go guess I am going to have to buy a master and booster.
I bought a junkyard MC because it was faster and cheaper at the time and to me was worth the risk I technically paid nothing for it.
Trav

 

Be sure you check the master cylinder push rod length...this is a very common area that is overlooked.

Great info in this thread: https://www.ford-trucks.com/forums/1...al-travel.html

 

Thanks RLA will check that and report back.
Trav

 

Ha!.. That's a laugh. Yes by design they are supposed to self adjust but I have never owned a Ford truck where they worked any good. My procedure for this is to jack up the rear axle so the tire is just off the ground, remove the little rubber plug on the bottom of the brake backer plate and rotate the star wheel with a flat blade screw driver until the brakes grab and back it off just enough to allow the wheel to spin. Repeat for the other side. Don't forget to put the rubber plugs back in. That should make a big difference in the amount of peddle travel needed to get the brakes to grab but you may end up with a situation where the rear is grabbing before the front. It's my experience that the front brakes should provide the majority of stopping power and if they don't then you need to replace the rubber flex hoses to the calipers. With that done and all the brakes bled if the rears are still grabbing before the front loosen the rears a little.

 

I adjusted them yesterday to that point and it did help a bit but still a lot of travel in the pedal so I put my old booster on and same thing cleaned my MC with brake fluid (flushed it a few times) and nothing put my old MC back on and nothing. When I put the old MC back on the light did go away but still the brakes suck big time. I drove it a bit down the road and I could barely stop the truck. I don't have to pump them anymore but I do have to go all the way down to the ground for them to grab and that is just barely that they grab.


I have done brakes on a 90 E150 and they did fine and I never adjusted them myself.
Trav

 

As Paul says, the drums are supposed to be self adjusting, but that's just a dream. 90% of the time a low brake pedal has to do with the drum adjustment. Put the rear axle up on jack stands and adjust the star wheel adjusters until you can hear the drums and shoes making contact. They're meant to always contact a little bit while driving (this drag is a large reason more cars don't still use drums, fuel mileage). By the nature of the truck, you'll probably never have brake response within the first inch of pedal travel.

Also, if your rubber brake hoses are old you may want to replace them. When they start to get old they'll expand and absorb some of the pressure before it's applied hard to the brakes.

That noise that you heard when disconnecting your booster is good. That means it's holding vacuum with the engine off. That's what gives you those couple of extra pedal pushes after the engine shuts down.

 

also going to chime in on the adjusters, have never worked on any of my trucks either, I always check them every other oil change, just use a screw driver

another way to check is push the parking brake down some and see how the brake pedal feel is

I believe it should have RABS, there is a bleeder on the valve you can open while bleeding the brakes to make sure no air is trapped

I had a 93 cab and chassis that I just could never figure out why I couldnt ever get the air out of the lines and had to pump the brakes to get it to stop, I replaced literally the entire braking system, well my wheel cylinder on the driver rear was bad right out of the packaging, took me 2 months to figure it out because of my own denial

 

We already adjusted them re bled the entire system and we got more brakes but not as much as it should be. Might re bleed it again and try it.
I just checked yesterday and it turns out I have no parking brake like I did before so I don't know what is wrong with that.
Trav