Deuce Brake Issues

[ASTFU]

First of all this sight is great. Thanks. My question on my 72 m35a2c. I pump the brakes 4-5 times to get the brakes to work so I guess its the master cylinder but when i took off the vent line on top and let off the pedal fluid shot out the hole is this correct? I replaced the air pack on my other truck and it stops great. I just dont want to start changing things I dont have to. Any help would be great.Thanks Thom

 

[gimpyrobb]

I would bleed the brake system first.

 

[Stretch44875]

Sure sounds like air in the system. The shooting of brake fluid could be you compressing the air in the brake lines. When you let off the brake, the air expands and forces fluid back in the master system.

 

[ASTFU]

Thanks I hope its that simple I will bleed the system tommorow and let you know, Thom

 

[WillWagner]

Make one of Kenny's power bleeders. They work great!
http://www.steelsoldiers.com/index.php?name=PNphpBB2&file=viewtopic&t=3439&highlight=r4x4

 

[spicergear]

Another bleeder that I've had success with is to use a low pressure 3-5 or 5-7 pound electric fuel pump and plumbed that into the vent line atop the master cylinder and force fed bled the system that way.

 

[acetomatoco]

Make sure the vent line is clear and be sure to bleed the booster first and put in your OHT while you are under there.

 

[m35a2cowner]

Brakes

Pumping the brakes to get them to work can be air in the line but it can also mean the brakes need adjustment. If everything is adjusted correctly the amount of brake fluid it takes to apply the brakes is minimal (fluids don't compress). If the brakes are out of adjustment then it requires more fluid to make the wheel cylinders move further to move the brake shoes out to contact the drum. It could take more fluid than one stroke of the master cylinder can provide (return springs pull on shoes which push wheel cylinders in to return fluid to master cylinder). Thankfully, or by design, the master cylinder piston bore fills faster than the fluid returns and therefore pressing the pedal again supplies even more fluid from the reservoir to the brake system. I bleed mine several times with very little improvement. I was able to improve braking application greatly (pedal height too) by adjusting the brakes. I also discovered that if your going to invest the time working on the brakes adjust both the top and bottom adjusters while your at it. Works a lot better than adjusting the top (easiest) ones only.

 

[m-35tom]

RE: Brakes

with the top off the mc, fluid will squirt out. normal.

 

[kipman]

brakes

How much psedal stroke is normal?

 

[kipman]

RE: brakes

I meant pedal stroke, need to take typing lessons.

 

[emr]

RE: brakes

A proper adjustment is called a"major brake asjustment" this is adjusting to specs the top and bottom, i think its 20 thousands at the top and 10 thoughsands at the bottom there is an access hole, each place... after years of adjusting the wrong way & a new air pac, new mstr cylinder new wheel cylinders still spongy! and now they are as sweet as can be when adjusted correctly, my peddle was always alittle spongy even after replacing everything, then a Staff sgt , at the armory hear, said Hey randy did u ever do a Major adjustment , HUH? whell he came over to my shop and did it, man that was sweeet, apparently 3000miles after a major adjustment U are supposed to do a Minor adjustment thats just the top, then another 3000miles do a major again, he said, so do it right and ask about the major adjustment before U go crazy, Randy

 

[m35a2cowner]

Pedal stroke

I would guess 2-3 inches is normal. Some is needed because that is the amount of fluid that needs to be released so that the brake shoes can move away from the brake drums. I am not sure of the proper military spec (movement) though.

 

[gimpyrobb]

RE: Pedal stroke

20 top and 10 bottom is correct. Adjust the bottom first, then the top. Like my dad always said, "you don't have to go, but you have to stop!"

 

[rosco]

RE: Pedal stroke

First Question: How did they get air in them? If you can't answer that, then its adjustment!

I agree that it is probably adjustment! Adjustment is commonly overlooked in all trucks that have juice brakes. You can try bleeding them, but I would start by a major adjustment first! Make sure the basics are properly set first.

Lee in Alaska

 

[acetomatoco]

RE: Pedal stroke

Don't forget to check the length of the pushrod on the MC

 

[johndeereman]

1968 m35a2 having a similar problem, 4 pumps of the pedal achieves normal brake pressure. Once the brake pedal is fully released, fluid begins rushing back into the master cylinder and in a matter of ten seconds the pedal fully depresses to the floor. The brakes bleed clean fluid, no air, no bubbles. Can there be a different issue or should i keep on bleeding?

 

[Howlin Mad Murdock]

johndeerman, please reread this thread, more specifically the posts about adjusting the brakes so that they will work properly. Those should tell you what needs to be done (besides reading the TM's). Hope you can figure your problem out !

 

[welldigger]

1968 m35a2 having a similar problem, 4 pumps of the pedal achieves normal brake pressure. Once the brake pedal is fully released, fluid begins rushing back into the master cylinder and in a matter of ten seconds the pedal fully depresses to the floor. The brakes bleed clean fluid, no air, no bubbles. Can there be a different issue or should i keep on bleeding?

Your air pack needs rebuilt or replaced. Air is bypassing the seals on the booster piston shaft.

 

[johndeereman]

johndeerman, please reread this thread, more specifically the posts about adjusting the brakes so that they will work properly. Those should tell you what needs to be done (besides reading the TM's). Hope you can figure your problem out !

Thanks howlin! I just wasnt exactly sure of the root of my problem. I just bought the truck and its my first deuce so im still learning. Thanks for the help