Brake line problem - HELP!

[Awesome Possum]

AP, let's take it by the numbers. If in fact your Deuce had brakes before you opened the lines, and in fact that is the only thing you did, then the problem is likely something you touched OR something not working properly as a result of what you did.

33 ounces is a lot to just disappear. Did it? Can you confirm that there is not fluid in the master? What happened when you filled it?

Proper procedure would be to fill the master completely, and then bleed it. And to refill as you went so that you do not reintroduce air. Is this what you did?

The air pack is kind of behind the master. You can lodcate the master, correct? easist way is to get under the truck and to watch what moves when you depress the brake pedal. Now, coming out of the master is a kinda short steel line that goes to another master-looking thing. When you depress the brakes, this thing will make an air sound. This is the air pack. If I am not mistaken, you want to bleed from the master to the airpack first. There is a bleeder right at the air pack.

I completely agree that you should download the TM and read it. But at the same time, this is a simple single circuit hydraulic brake system just like most others. Except it is bigger and the air pack in the line works off positive pressure as opposed to the Hydrovac-type boosters that worked off vacuum (think mid-50s GM cars and Jaguars).

So anyone who understand the concepts of a hydraulic brake system can work on this and troubleshoot it and figure it out. If you friend is uncertain, and no offense meant, then find someone else locally who can chime in. A telephone consultation might work but sometimes there is no substitute for eyes right there looking at it.

I am sure that no offense was meant by anyone on this thread. You must admit it is kind of scary to think f a 13,000 lb vehicle with faulty brakes. hence a high level of caution in general. Don't take it personally, we all had to earn our bones and now is your turn. That is meant in a good way.

I appreciate your words. Much of my frustration comes from the fact that I'm not working on it myself because of the bad elbow. I did email the tech manual to my mechanic and he'll go over it. I'll also print out a copy as well. Yeah, a brake system is nothing to mess with and that's the point of setting up a little consultation in advance for Sunday when he'll be there. Not a complete how-to over the phone, just maybe something not covered in the TM. I spent most of my career working with people on the phone, so I have a lot of faith in it.

Again, I know the dangers of having a bad brake system and want to get ALL the help I can get. A TM is knowledge; a man's experience is wisdom. I'd like to get both so I know the thing will stop when I ask it to. No one's life is worth it over utter faith in only one source of info. I'll not "earn my bones" at the risk of hurting someone. There's a big contradiction between being safe and learning to do it without asking for help. It is obvious, however, I'm not going to get help here. Lesson learned.

 

[dilligaf13]

I've recieved both good help and smarta$$ comments on here. Unfortunately when dealing with peple you have to take the good with the bad. For the most part I've been fortunate but my advice to you is tell the good ones thanks and the bad one to eat a bag of d!ck$.

 

[Awesome Possum]

I've recieved both good help and smarta$$ comments on here. Unfortunately when dealing with peple you have to take the good with the bad. For the most part I've been fortunate but my advice to you is tell the good ones thanks and the bad one to eat a bag of d!ck$.

Very good advice indeed, though I'm trying to avoid this last suggestion (but I am thinking it). I did get a supportive PM this AM, but he hadn't bled brakes in awhile. I just talked to my friend and he's been going over the TM and said that things looked normal for a brake bleed, but he hadn't even gotten to the airpack part. He's looking it over some more and trying to understand the system. He is Army and is used to TM's, but he's a ground-pounder and not an army truck mechanic (Though as a civilian he was). He still has some questions someone with experience could take 5 minutes to answer. Getting someone to help by talking to him on the phone is no different from all the times people have offered/asked to have someone over to help them with something. Someone wrote of this on this very thread.

I'm just faced with telling my son that we are not going to the SS Rally next weekend unless we get this fixed tomorrow. Me, I don't want to sleep on a cot in the back of an M105. He's been bugging me for 6 months now and I'm trying my best to make it happen for him. I also don't have the financial means to have it towed 50 miles to the nearest place that does understand the system. More time has been spent on telling me why my request is unreasonable than it would for someone to talk to my guy for a few minutes. What's up with that?

BTW, my number is 254-228-6503.

 

[Awesome Possum]

I have the help we're going to need tomorrow to get our truck up and running! My thanks go out to Littlebob and to Doghead who have both graciously offered to help. Thanks guys!

 

[plym49]

The air pack is just an in-line power booster. Here is how it works. Usually the master cylinder is connected right to the wheel cylinders. You step on the pedal, the piston in the master moves and pushes brake fluid, and that brake fluid in turn moves the pistons in the wheel cylinders.

Now add conventional power brakes, like those found in most cars. Engine vacuum is used to amplify your leg pressure - the power booster sits on the firewall between the pedal and the master - so you don't have to step as hard to apply the brakes. And the master is still directly connected to the wheel cylinders.

But there is another way. Instead of amplifying your muscle pressure, we can amplify the fluid pressure in the lines.

In the Deuce, the master connects to another device called an air pack. The air pack is just another piston inside a cylinder, kind of like a wheel cylinder. You step on the brake, the master cylinder piston moves and pushes brake fluid through the line, and the piston inside the air pack moves. The air pack is special in that it can use air pressure to amplify the pressure exerted by the master cylinder. The piston inside the air pack, in turn, connects to the wheel cylinders.

If you think about it, this is why it is hard to install dual brakes on a Deuce. With te setup in most cars, where the power booster assists your leg pressure, you can have a dual master cylinder. With an in-line power booster system that assists the line pressure, you would need two air packs and dual masters to feed a dual system.

The Deuce is a big heavy truck and uses high air pressure to help assist the brakes. On cars that do not need as much assist, and since a gasoline engine has vacuum, some manufacturers made air pack-type power boosters that ran on vacuum instead of pressure. Bendix was one manufacturer, and the units were called Hydro-Vacs. They were tits for adding power brakes to the cars of the 50s that had the master cylinders under the floor. Master cylinders were moved to the firewall to give enough space for the leg-assist power booster we see today, because they would not fit under the floor. Power boosters are less expensive to manufacture and they last longer, so Detroit went to them.

Now you see why you want to bleed the bleeder at the air pack first. You want to be sure good fluid with no air is getting to the air pack. Then you bleed the wheel cylinders to get the air out of the lines from the other side of the air pack piston to the wheel cylinders.

I hope this explanation helps and that it makes sense to you.

 

[Mike O.]

Doghead...while STFA or TM would be an easy answer...the fact that he apparently followed some basic brake assembly and bleeding protocols and then went through that much fluid means he likely has a leak somewhere. I think he's looking for guidance on where to look rather than a beatdown.

My $0.02.

Mike O.

 

[doghead]

Yeah, that's why I called him and told him to have his mechanic call me. So I can "beat down" his mechanic too!

 

[Awesome Possum]

I think I know where that extra brake fluid went to. The original problem with the brakes was that the 3 way brake line junction that is under the drivers side of the cab, about 3" in, got stripped when I put it together. When I got it all hooked up I tried pumping up the brakes. Yeah, now I know it was dumb, but it must've leaked alot more than I even suspected. I hate to admit to doing this, but everyone has been great about helping me out with this, so I gotta' 'fess up on this one. Hopefully by tomorrow PM I can report that everything is as it should be, and I have little doubt of this.

Thanks again to all!

 

[Awesome Possum]

WE got it going today. WOO HOO! My guy went on Steel Soldiers and read up on everything he could, and the first thing he tried was adjusting the brakes. He believes that it was the other axle that was stopping the truck before and that this axle was terribly out of adjustment. Got 'em all adjusted and the brakes work great. Took it around the block and nothing fell off, even after taking it up a rocky hill that at least looked vertical to us.

Thanks to everyone who helped on this, and special thanks to Doghead and Littlebob who made themselves available for any special help.

 

[doghead]

I'm very happy to hear you figured it out and I hope your plans for next weekend work out for you and your son. It was very nice talking with you.