Brake Issue

[skokie]

How can I tell if a booster is bad? Truck is a 68 with drum up front and in back. I had to replace the front lines and I have bled about 2 cans of brake fluid through the system. Pretty confident that there is no air in the line ( but have been wrong before). Could this be a bad check valve or bad booster?

With the engine off the pedal is kinda firm but as you push it it will not get hard. It stays the same.

Thanks

[68gmsee]

Originally Posted by skokie

With the engine off the pedal is kinda firm but as you push it it will not get hard. It stays the same. Thanks

Need a little more info than that to answer your question. Not sure what you mean about pedal being firm when engine is off and will not get hard.

On my truck at least, the pedal is firm when the engine is off. When you start it, the vacuum will assist the pedal and become easier to depress.

Let us know what problems you are having with the engine running...

[skokie]

With the engine off if you push the pedal in it it will get harder and harder to push until it gets to a certain point. With the engine one Its very easy to push the pedal in but its like the brakes are not grabbing. I have bled this sucker through 2 small cans of fluid. I just got back from the parts store with a new check valve and 2 huge cans of fluid. Just in case

[jhow66]

Here's how to check your booster:
1--engine off -step on pedal until firm-hold
2--start engine-if pedal drops some it is ok

Easy way on to bleed on 4wheel drum:
1--get 4 clear glass (don't let old lady see you )
2--pour a little brake fluid in each one and set by each wheel
3--attach a piece of hose to each bleeder and run it to each glass so that the end is below fluid level
4--open all bleeders and let gravity bleed them for you
5--when no more bubbles come out of hoses, close bleeders
(keep master full)

[skokie]

Well after doing some more checking I found 1 thing for sure that was a issue and another Im thinking is a issue. The one thing I found for sure is that the nuts holding the lines on the master were not tight enough. I found a small leak. I have tightened these up, cleaned them up and tested and no more leak. The other thing that I think may be the issue is that the pedal rod may be adjusted to far in. I did take it off when I was working on the column so I may have jacked that up. Any idea how many threads in you should be on that rod?

[poorboy]

Are the brakes adjusted properly? On a drum/drum setup it will affect the pedal feel if they are not.

[jhow66]

Brake pedal should have a small amount of free travel.

[skokie]

Poorboy before I tore the truck down for the work I did to it the brakes were working fine. The only things I have have changed are the hard lines from the master cylinder to the drums ( hit the originals with the engine and they snapped like a twig). I also messed with the rod length at the brake pedal. After doing some searching I found out that 4-6 threads from the end is about where it needs to be. I also found the original spot on the rod today after doing so serious looking so now I have that back to where it is supposed to be. Now I am heading back out and I am going to bleed out the entire system again. Its gotta be air somewhere. Just my luck LOL

[68gmsee]

If you do it with the 4 glasses/jars you should be able to remove all of the air from the lines. I do it individually myself and I start with the brake farthest from the master cylinder.

Don't discount a bad master cylinder if the brakes are not grabbing as you say. Usually, air in the lines make your pedal feel spongy and you can pump it and they should grab. If this doesn't happen, you could have a bad seal inside the master cylinder.

[skokie]

Here is a pic of the lines I replaced. I think I am going to head to the store and get some clear tubing and try that gravity bleed. How long does that usually take?

[68gmsee]

Did you do the master cylinder bleed trick when you replaced the lines? They're pretty persnickity about bleeding the air out.

It looks new to me, but still could be a bad seal. I bought one from a local auto store and had to take it back because the seal either wasn't installed right or broken. Foot pedal went all the way down even after bleeding like mad.

I've never done the 4 jar method, but I assume your longest time is going to be setting up the tubing and the jars with fluid in them. Once you step on the brakes a few times and don't get any bubble you're done. May need an assistant. Mine is usually my wife (much to her dismay)

[skokie]

I bench bled the master before I installed it. Im looking for tubing now.

[skokie]

Ok here is the latest. My neighbor came over and we bled it out. I started at the right rear and it took us a hour. When I got to the pass front all I got was air for about 15 mins. So I moved on to the drivers front. Got the air out of that one. Moved back to pass front and got more air from there. Moved back to drivers front got some more air then it cleared out. Looks good and the pedal is a lot stiffer.

[68gmsee]

All right!!! Amazing how much air got sucked into the lines. I had a Tahoe that did the same thing. Seemed to spit and sputter forever before all of the air came out...