Brake Pedal - Power Assist Issue

[7Dust]

First, please go easy on me for not searching. I was not able to find a brake thread that quite explained what I am experiencing with the brakes on my Deuce and I definitely want to get this right. As much as driving the truck brings a smile to my face... sometimes the brakes nearly scare the **** out of me!

1. At the first press of the brake pedal while driving or with the engine running, the pedal goes nearly to the floor. It does brake somewhat but the pedal travel is extreme and the brakes do not apply until the very end of the pedal travel.

2. If I release the pedal and immediately reapply the brakes, they seem to work normally. Not sure what normal really is since this is my first time driving a Deuce.

3. However, sometimes if I press and reapply the pedal it will be very hard as opposed to being very soft. This is kind of scary because I have almost no brakes when it decides to do this. If I have the state of mind to release the pedal and reapply sometimes they will start working again.

4. If it matters to the problem, the handbrake is adjusted all the way tight and does not work at all.

I am thinking this could be an air pack problem but its seems that this is one part that is kind of expensive to be guessing with. Is there a test procedure to troubleshoot this and where do I find it?

 

[whyme]

same prob here, think its air in the lines. ive got to bleed them again and see.

first off, are you losing fluid? and the hand brake is independent of the rest of the brakes

 

[markmontana]

It would be nice to assume you have done a complete maintenance of the brake system on your truck, as found in the manuals, and also other info in the 'Resource' section. But if you haven't done a thorough brake service, that is where you start. Even if the brakes appear and feel ok, many of us go thru the brakes ASAP when we get a truck, and then watch and service them often.

Do you have a friend or know anyone with a deuce that could help?

 

[WillWagner]

It could be that they need adjustment. These aren't like car or truck brakes, they do not self adjust. Go to the resources section and download the TMs that pertain to the brakes. You should pull the wheels and drums and do a complete service/check just for your own piece of mind.

 

[M543A2]

I think it is very possible you have both problems mentioned here. You could have air in the lines somewhere and brakes that need adjusted. The hard pedal can be caused by the combination of air and out of adjustment allowing the air pack cylinder to bottom out.
Look inside all of your wheels at the brake drum and tire to see if you see wet areas from leaking brake fluid. When adding fluid, do not forget these use silicone fluid. Never add regular brake fluid to the system as you will get a jelly in the reservoir and a real problem!!

Regards Marti

 

[Blood_of_Tyrants]

Bleed the brakes (DOT 5 fluid only) and check the brake adjustment. As for the hand brake, loosen the adjustment on the brake handle and crawl under the truck and adjust the nut on the brake lever.

 

[bugei]

+1 for the airpack being the problem. this sounds very much like the airpack might have been rebuilt "wrong". there is an error in the tm that puts a critical part in backwards and the "hard pedal, no brakes" is the symptom.

http://www.steelsoldiers.com/deuce/7623-airpack-rebuild-warning.html

 

[7Dust]

No, I have not read any technical manuals yet - but I will read everything! Just give me time. I just found the resource section (duh) so I guess I'll be busy for a while. I do intend to slowly work through every issue on the truck but just to get me going for a while I wanted to find the particular source of the barke pedal issues and fix it instead of throwing a lot of guesses, unnecessary parts, $$$, and wasted time. I'm going to clean the master cylinder area today so I can check the reservoir. Its nastee under there and I don't want any crud to contaminate my crappy brakes.

Handbrake issue is clear. The handbrake pad is worn down to practically nothing (1/16" - 1/8" thickness only) Looks like there is maybe just 1/4" left of adjustment on the brake pad side of the cable but I could not get the nut to move either direction. Looks like a locking nut of some kind - is there a trick to releasing it? Anyhoo, I zip tied a flare wrench to take up the space between the nut and the parking brake actuator under the truck for a temporary fix until I can find a replacement pad set and / or figure out how to get the cable to adjust on the brake pad end. At least I can park the truck without it rolling now. I need to find a good inexpensive source for the parking brake pads. Even a good used set should work since I don't plan on driving around with the hand brake on.

 

[AZDeuce]

Ok, the mushy pedal is due to air in the lines. I had no leaking brake cylinders on my deuce, it took me months to FINALLY find a SMALL leak at the rear axles flexible brake line, it had the smallest damp spot, and I would never had recognized as a leak. But I found it after pumping the brakes alot and holding the pressure.

Check for leaking wheel and master cylinders, if everything is ok, pump the heck out of the brakes and hold the pedal down and see if it starts dropping to the floor, even if it doesn't, then get under the truck and look for wet/damp spots around your flexible hoses. Of course make sure they're clean and dry BEFORE you start this procedure. so you can see when the dampness starts to reveal itself.

If you find one slight damp spot then REPLACE ALL of the flexible brake lines! If one is bad, the rest probably aren't too far behind.

Now the pedal getting harder so you can't activate the brakes is due to no oil in your air pack. There's two style airpacks, one has a plug you can remove and add oil, the other does not, and requires you to remove the "J" shaped pipe that runs from the rear center down the left side to the front of the airpack. Either way once you have it opened up, add 4-5 "good" squirts of machine tool oil in there. I put 9-11 squirts in mine, and haven't had a problem since.

I learned all this stuff by myself, except for the air pack oil, that I learned from some helpful folks on this site, so I thought I'd pass along the information.

DO NOT drive the truck until you get this sorted out! For your's, but mainly for other's safety.

 

[Garandfan]

Just to add my 2 pennies..... Considering I just went through this recently. If the pedal goes to the floor, you have to bleed the master cylinder. Just take off the cap and start pushing the pedal. You will see air bubbles. Keep pushing until the pedal gets to constant height. Then bleed the airpack. There are plenty of threads. Maker a power bleeder and bleed the wheel cylinders. Plenty of threads. If your pedal gets hard over the course of driving.... This is a sign that you have a bad airpack. If you let this go on for too long, your breaks WILL lock up on you! If they lock up, you will have to crack the bleeder on the airpack to release the brakes. Hope that doesn't happen to far from home.

You should keep the air pack oiled! If you strip the allen screw, you have to disconnect the "J" line on the back to get oil in. But if your brake pedal is getting hard, it's already too late. REPLACE THE AIRPACK!

 

[7Dust]

1. Replaced the master cylinder with a new one - it came with the truck so figured why not try it.

2. Bled the air pack and all wheel cylinders until all old fluid was flushed out. Used DOT 5 Silicone fluid.

3. Pulled the J-pipe from the rear of the air pack and lubricated with machine oil.

Verdict: No change. First pump on the brakes takes the pedal to within 2" of the floor. The brakes seem to stop okay but the pedal travel is excessive. The second subsequent pump of the brakes brings the pedal up higher. If you do not use the brakes for a few seconds, the process starts again.

If I simply hold my foot on the pedal after pumping it once, the pedal does not fall. The pedal only "falls" when it is not being used for several seconds.

As far as the occasional hard pedal - I cannot figure out what causes it. It happpens randomly and infrequently. When this happens, there is still braking but the braking effort required on my foot is greatly increased.

I guess the next step is to pull the wheels and look into adjusting them the brakes individually. I don't own the sockets to remove the wheels yet so that is my next purchase.

Wanted to update everyone on my progress because I find there are so many brake threads but no one ever updates them when the find success and get their problems sorted out. Maybe someone will find this thread useful in the future.

Finally, not really related to my service brake issue but figured out the hand brake did not set because it was already adjusted to the end of the threads on the cable under the truck. I zip tied a flare wrench to take up about 1/4" space on top of the adjusting nut on the cable and I at least have a hand brake now for parking. I will get back to this after the service brakes are sorted out

 

[Barrman]

Read the -20 manual about a "major" and a "Minor" brake adjustment. Yours sounds like it needs both. Many threads have been written about brake adjustment. It is really a very simple process that takes longer to jack up the axle than do. However, since this is a new to you truck. I would suggest pulling the tires off and pulling the drums to inspect them, the shoes and just about everything else you see. Do this on all 6 corners with the adjustements done afterwards. You will have a high pedal that tries to throw you through the window.

 

[7Dust]

^^^ I'm trying to understand the mechanics of what is happening to the brakes on my truck. Specifically how the pedal falls when not being used but does not fall if I hold my foot on it.

This is just to satisfy my need for knowledge.

 

[Barrman]

Ok, you push the pedal, a piston in the master cylinder pushes fluid through the lines toward the wheel cylinders. If your shoes at all 6 corners are far away from the drum, a lot of fluid is needed to push them up next to the drum. That takes the entire master cylinder stroke length. You let go and quickly hit the pedal again. The shoes which are pulled away from the drum by springs didn't really have much of a chance to move back. Now, only a little bit of the master cylinder piston stroke is needed to push the shoes against the drum. Nice hard, high pedal.

Pull your master cap and pump up the brakes until they are high and hard. Let go of the pedal and watch how much fluid squirts back into the master. As soon as it is done squirting, hit the pedal again. It will be low.

All a minor or major adjustment does is move the shoes closer to the drums. Getting rid of all the extra fluid needed to move them there where they are supposed to be adjusted to in the first place.

That make sense?

Now, air in the lines makes the pedal feel spongy. You say your pedal is firm, so bleeding the brakes won't help you any.

The air pack was left out of my writting above. All it does is put more pressure behind the fluid going to the wheel cylinders. Yes, a low pedal will be higher with the air system charged and the air pack working. However, you should have a high hard pedal with no air in the tanks and the engine off. Except, because the air pack has springs in it. The pedal will feel a little springy which is hard to describe besides saying if you push real hard, it will push real hard back in a funny kind of way. Have the air tanks full and that push back isn't there.

 

[JOAT 0311]

Doing brakes soon! Like what I see hear, Thanks!

 

[7Dust]

Ive searched and searched... til my searcher was sore.
ummmmm what socket sizes do I need to remove the wheels?

 

[Barrman]

1-1/2" BUDD socket. The socket you need is for semi trucks. It will have the 1-1/2" for the outter rear and front lugs. Then inside, it has the 13/16 square drive needed to pull the rear inner lugs. Most NAPA stores have them, as well as truck stops and just about anyplace that deals with heavy equipment

Here is the fun part. Once you find the socket. You will realize it is 3/4" drive. That means you need an adapter to make your 1/2" impact gun fit. But, you will eventually break that adapter. Then you get to go shopping for a 3/4" or 1" drive Thunder Gun. More tools!

 

[kbush]

7Dust, you have the exact same issues with you brakes that my truck had when I first bought it. Including the parking brake. Read the technical manual to adjust your parking brake. Very easy to do. When you are done, put a spot of primer or something on the drum that the parking brake grabs, drive around a bit, if the paint is still there, you know your brake is releasing all the way.

On your hydraulic brakes, I replaced my air pack and my master cylinder, after giving up on bleeding. Bleeding doesn't do anything if you have a faulty air pack. Once I replaced the MC and air pack, I did the first brake adjustment procedure, the easier of the two. This one you can do without removing wheels. It's all in the TM. Basically jack one wheel at a time. It's easiest with two guys. Near the bleeder on the backside of each hub you will see two bolt heads, those will adjust each shoe.

After I replaced the MC and air pack, the pedal still went to the floor but it was a LOT better than it had been. There fore I don't know how bad my air pack really was, but I still haven't regretted changing it. Then after I did the adjustment, my pedal is rock hard after it travels merely and inch. I have locked my brakes up EASILY on dirt roads, just testing the brakes.

The brakes on these trucks actually work pretty good if they are maintained properly.

 

[kbush]

Also, please do us a favor and STOP driving your truck until you get the bloody brakes fixed! I mean if you haven't stopped completely already.

 

[Barrman]

You are correct and I am wrong. I changed the original post. Thanks.