Brake Bleeding

[URSATDX]

Noticed a small leak on the drivers side metal brake line that runs from the junction to the top of the rear wheel

where the bleeder is. I am going to remove the line in hopes of finding something local (Napa?).

When the line is replaced do I bleed the brake system as I have always done in the past on other vehicles?

2 people, one applies the brakes while the other opens the bleeder, repeating, until all air is removed?

Do the air packs have to be bled also?

Thanks in advance.

 

[Valence]

Yes, the air pack does have to be bled, and should be the first (while someone is applying the brakes). After that, you can bleed the brakes like you do all of your other vehicles, using two people just as you described. Start at the wheel cylinder farthest from the master cylinder, and then the next closest and so forth, also just like your other civilian vehicles. I find the bleeding more effective when the air tanks are full. It's easier (and safer) to talk to your helper if you don't have the truck running to keep the air tanks full, but instead use the passenger rear "emergency" glad-hand connected to a shop air compressor.

Make sure you know if your truck has been filled with DOT 5 or DOT 3 brake fluid so you add the right type as you do not want to mix them.

If you search the site for a "power bleeder" you can find how to use a weed sprayer to make it a 1-man operation. Since I have a "remote brake fluid reservoir" I still prefer the 2 people method.

Where I put my remote reservoir (makes checking and refilling the brake fluid level so much easier, and gives me more fluid in case of a leak):
https://www.steelsoldiers.com/showt...ce-this-week&p=1706688&viewfull=1#post1706688

Example of where to buy:
https://www.bigmikesmotorpool.com/products/remote-master-cylinder-reservoir-kit

 

[m715mike]

Check out the Deuce Stickies...

https://www.steelsoldiers.com/showt...LINE-REFERENCE-GUIDE-(Sizes-lengths-fittings)


https://www.steelsoldiers.com/showthread.php?3229-Deuce-Power-Bleeder-R4x4-Style


Also, the TM is a good reference.

 

[texas30cal]

They've got you covered!!! The power bleeder is DEFINITELY worth making and using, much easier and better at pushing the air out than pumping the pedal, esp with the thick dot 5. The remote reservoir is a must have.

 

[texas30cal]

I forgot to say good catch on that leak, it's small and lots of folks wouldn't catch that. Secure that junction block, vibration could be the culprit or at least a contributor.

 

[patracy]

I have misplaced my power bleeder setup. I need to make a note of picking up another sprayer when I go get grass seed!

 

[dmetalmiki]

I do agree the separate remote reservoir is a must, especially with the single line braking systems. Just another safety precaution well worth carrying out.

 

[WillWagner]

As long as the system did not drain, the line can be replaced and just the wheel it goes to can be bled.

 

[URSATDX]

I'll probably get my Father to help with bleding the brakes. He's mid 80's and really loves the truck.
Its a bobbed M35A3. It has a large brake reservoir on the P/S firewall.
It has dual air packs. Do these get bled in the same way, Dad pushes on pedal, I open and close the bleeder, repeat?
What have you guys used to prevent the pedal from going too far and damaging the master cylinder?
I will, no doubt, build a pressure bleeder for future use. It's just better with my Dad helping out.
Thanks again.

Yes, the air pack does have to be bled, and should be the first (while someone is applying the brakes). After that, you can bleed the brakes like you do all of your other vehicles, using two people just as you described. Start at the wheel cylinder farthest from the master cylinder, and then the next closest and so forth, also just like your other civilian vehicles. I find the bleeding more effective when the air tanks are full. It's easier (and safer) to talk to your helper if you don't have the truck running to keep the air tanks full, but instead use the passenger rear "emergency" glad-hand connected to a shop air compressor.

Make sure you know if your truck has been filled with DOT 5 or DOT 3 brake fluid so you add the right type as you do not want to mix them.

If you search the site for a "power bleeder" you can find how to use a weed sprayer to make it a 1-man operation. Since I have a "remote brake fluid reservoir" I still prefer the 2 people method.

Where I put my remote reservoir (makes checking and refilling the brake fluid level so much easier, and gives me more fluid in case of a leak):
https://www.steelsoldiers.com/showt...ce-this-week&p=1706688&viewfull=1#post1706688

Example of where to buy:
https://www.bigmikesmotorpool.com/products/remote-master-cylinder-reservoir-kit

 

[URSATDX]

Weather prohibited my Father from coming this morning to help with bleeding the brakes. I put together a pressure bleeder following
the many helpful posts from everyone. When I pressurized the large plastic brake reservoir (dual system A3) the modified reservoir cap leaked
fluid. This was a new Dorman cap that seemed to fit quite well. I was hesitant to drill a hole in on of my exisiting caps but did, and same thing.
At $26.99 a Qt I was unhappy. I emptied the sprayer and tried again with just air knowing I'd have to keep an eye on the level in the reservoir,
still leaking but air this time. I tried to modify the rubber gasket to improve the seal with no luck. Ordered a new cap and gromett to replace the one
I drilled. Dad's coming in the AM. I'll try the old fashioned way.
How do you prevent the pedal from going to the floor and possibly damaging the master cylinder?
Are the Air packs (2) bled in the same way (push pedal, loosen bleeder, close bleeder, etc.)?
Thanks again to all.

 

[Valence]

When I pressurized the large plastic brake reservoir (dual system A3) the modified reservoir cap leaked fluid. This was a new Dorman cap that seemed to fit quite well. I was hesitant to drill a hole in on of my exisiting caps but did, and same thing. At $26.99 a Qt I was unhappy. I emptied the sprayer and tried again with just air knowing I'd have to keep an eye on the level in the reservoir, still leaking but air this time. I tried to modify the rubber gasket to improve the seal with no luck. Ordered a new cap and gromett to replace the one I drilled.

I was under the impression that the power bleeder was to be connected directly to the top of the master cylinder via a barbed nipple, bypassing the reservoirs, but the M35A3 is a bit different than the M35A2 in that regard as I had to add my own reservoir. This is why I don't care to use a power bleeder as I don't want to remove my reservoir. Two people work great for me and I don't have to crawl out from under the truck but to add more brake fluid.

How do you prevent the pedal from going to the floor and possibly damaging the master cylinder?

I have never read about "the brake pedal going to the floor and possibly damaging the master cylinder". That doesn't mean it doesn't exist and something you should be prevent, but I've never read of that being a concern if it happens. (I.E.: You drain too much fluid and fail to close the bleeder before the pressure cuts off and the brake pedal reaches its maximum travel limits)

Are the Air packs (2) bled in the same way (push pedal, loosen bleeder, close bleeder, etc.)?

Yes, the two air packs are bled in the same way, just as you described. In my opinion, it helps if you have full air pressure in your tanks to properly work the air packs, and more/better pressure to push the fluid and bubbles out of the brake lines. Since the M35A3 is a dual circuit system with a dual reservoir master cylinder, one air pack is for the rear tandem axles and one is for the front axle.

HOWEVER, from your one picture, it appears that your truck doesn't have rear tandems as it has been modified (aka "bobbed") so there's no telling how it's been modified from original. It could be done logically and done well, it could be a crazy mess or somewhere in between.

 

[URSATDX]

1st off I'm terrible with trying to sift thru TMs for info.
My A3 has a large yellow plastic brake fluid reservoir on the passenger side of the engine compartment on the firewall.
Best I can tell, judging by the brake pedal linkage, is the master cylinder sits inder the drivers seat and is fed by this large plastic
reservoir.
I have lifted any and all of the floor insulation that I could without removing my seat to look for an access cover.

I have read here, and elsewhere, that pushing the brake pedal fully to the floor can damage the M/cylinder.

Might just put Vice Grip pliers on the brake pedal rod to prevent it from reaching the floor.

Thank you for answering my question regarding the procedures for bleeding the air packs.