brakes

[Buddy]

I ave replaced everything on my truck as far as brakes go. The only thing i never did was the master and the booster. I noticed today while I was still trying to get the timing right that the pedal felt super hard and the truck didnt want to stop. I dont drive this truck yet as it is only half built. i wanted to know is a super hard pedal a sign of either the booster or the master being worn out? I double checked it to see if there where any other things it could be and everything else seem\s in order just a rock hard pedal. Keep in mind that I am only moving this across my yard and it is sometimes hard to tell whats up.

[Lt.Del]

that's a sign of booster messing up. I've had to replace my booster in the past.  however, before you replace it, check the little plastic check valve that plugs into the bookster (where the vacuum hose connects to booster).  That could be bad and same symptoms will result.
Also, check to ensure you are getting vacuum at the booster.

A bad master cylinder would make the pedal go down too easily and very soft pedal.  You'd have to pump a few times to apply brakes.

At least that has been my experience.    I had to replace the booster on my '79 after i had to apply all my weight and stand up on the brake pedal to make it stop.  Not a good feeling.


this should help some.... http://forum.73-87chevytrucks.com/smforum/index.php?topic=5202.msg24781;topicseen#msg24781

[snibook7537]

yup I agree with Sgt Del. funny story my buddy's 79 f-150 had a similar problem he had no pedal at all then he replaced the master cyl and got a little bit back, the next day the pedal was spot on maybe a little soft and it wasn't running for it's life. I figured the master cyl is still bad but the booster lost vacuum somewhere. Stupid ford needs kingpins for the dumb twin I beam front suspension so I had to drive it cause he was afraid of it. So messed up master cyl, broken Vac check valve (no power brakes) that we had to plug so it didn't have a vac leak and the worst steering in the world. Was a fun trip, I think he still has yet to put a good master cyl in it but went to NAPA and got a $10 valve instead of using the one we got out of a Junk Yard for basically free.

[Buddy]

I checked the booster I have all kinds of vacum from the line going in. not sure if that means my booster is bad.

[VileZambonie]

So after you shut the engine off and you let it sit for a few minutes des the booster maintain vacuum?

[Buddy]

Not dure on that one. should it still have vacum after the motor is off and if so for how long

[Layne]

Yes and until you press the brakes again it should still have vacuum.

[Lt.Del]

when they say it will have vacuum, that doesnt mean the line will still be pulling vacuum.  The diaphram should still maintain vacuum inside it.

with engine off, pump brakes a few times, hold pressure on the pedal and turn engine on and see if pedal moves. It should only go down very, very slightly. If it goes way down, you have  a rip/hole in diaphram.

does it create a wooshing sound when applying brakes? 

[Buddy]

yes, it does make that sound when applying brake. If the truck still has vacum after I trun it off, does that ,ean my booster is good? also if I pump the brake with the truck off and that turn it on and the pedal only moves a little does than mean the booster is good. I have also noticed that the seals around my master cyclinder started leaking as well now, I just can't win.

[VileZambonie]

The truck won't have vacuum after you shut it off the booster will. Does it?

[Irish_Alley]

I have also noticed that the seals around my master cyclinder started leaking as well now, I just can't win.

What seal? Between the cylinder and booster or reservoir and cap?

[Buddy]

ok you guess have me confused a little. Tonight I replaced the master cylinder, not only to rule that out but it was way over due. This is what i did. i tried pumping the brake with the truck off and than turned it on, if the pedal moved at all it was very very little. Started the truck and took the vacum line going into the booster off and it has vacum. Put my finger over and very little change in the motor. ( someone told me to try that) I started the truck and than turned off and than pulled the hose off agin it still had pressure. So thstwhat i have done. It is hard to tell only moveing the truck 5 to 6 ' at a time to see how the brakes are working. It just seems that they are not working the best. I also forgot to metion that everything other than the booster is now brand new, I am also running 35" tires.