Air over Hydro Brakes in op (M35A2)

[cucvalbanese]

Hi everyone,

Yes, this topic has been covered. I have checked the forums and didn't see my symptoms in them. I have also looked at my TMs in my garage but cannot find my troubleshooting TM. Looked at the forum TMs and can't remember the TM number and the ones I read through don't have troubleshooting.

So.... In January I went on a trip down the California coast to Big Sur for a weeks long camping trip with the deuce. It was awesome and lets just say there were some jealous campers and guys hiding there wives hahaha. Prior to my trip and any others I do I did PMCS on everything. No leaks, air or fluid. Upon checking the master cylinder I noticed that the fluid was lower than normal but well within the safety range. Instead of leaving it alone (the coast to Big Sur is on a 200-300' cliff to the pacific ocean) I wanted to play it safe so I went and bought new DOT 5 Silicon fluid and brought the fluid level up to TM specs. Trip went great and I didn't go off a cliff T.G.

Last week I went to take the truck on a 10 mile warm up trip. Did PMCS, no leaks everything G2G and breaks working great. A block away from the house coming up to a stop sign, I applied the brakes and the pedel went to the floor.... Good thing I was on my toes and down shifted quickly and gingerly used the hand break and still stopped prior to the line.

The streets were not busy and after a half hour of looking things over I decided to drop the truck into low and stayed in 1st and 2nd driving like a lumbering snail back home.

So.....

No fluid leaks
No air leaks
Sudden peddle to floor
Getting 100PSI in tanks
Brakes worked like a charm prior

Anyone every gently tap the Air Pack with a ball pin before to see what happens?

 

[clinto]

If it didn't lose fluid, my first thought would be a dead master cylinder. You can test this theory by removing the brake line output and plugging the hole. If the pedal is rock solid then the problem is further down the line. Reinstall the brake line and cap the airpack output.

It's gotta' be one of the two.

 

[Keith_J]

Sealed master cylinder can develop a vacuum with temperature changes and stuck breather. Then each wheel cylinder cup will suck back just enough to prevent brake action.

 

[gimpyrobb]

Ever adjust your brakes? It doesn't sound like the root cause, but it could amplify other issues.

 

[cucvalbanese]

Sorry for the delay guys.... Moving next month so packing up two houses and having kids unpack your already packed boxes has been frustrating.

Here is the skinny.... #1 Don't trust your friend to come help.... the Master cylinder is not full.... its empty.

I went under the truck with the head lamp and found brake fluid on the cross member under the master. Squeezed my head in to find the hidden leaker.

It was the brake line which passes underneath the bottom back of the master. Vibration caused a hairline crack in the line. I will be installing preventive measures on the replacement line.

The line looks like it comes from the passenger front wheel, inside the passenger side frame rail. It turns right onto the cross member rail and passes under the back of the master then takes a left and ends up at a thread about a foot behind the master on the drivers side frame rail. In other words an S turn in the frame rails.

looks like I have to pull it and find a shop with the right size and that can bend it.

 

[cucvalbanese]

This explains my lack of puddles under the truck as the crack only leaked when I applied brake.

Confirmed: Front right brake line is the one I need to replace.

Any tips?

 

[cucvalbanese]

So after looking the brake line over this is what I have in mind.

1) Remove line from brake hose at the front passenger wheel.

2) Use a tube cutter to cut the line at the middle of the cross member.

3) Take out bad section of line, bend to fit new line and use a fitting to affix new line to old.

4)Bleed brakes with an auto bleeder

5) Wrap strips of tire inner tube around vibration points and below the master cylinder.

 

[rustystud]

If you have one line that has already cracked you'll have more. It's time to replace the whole system. Look at "Peashooters" lines he sells. Also his post will help you get any other lines you will need.

 

[DavidWymore]

Has anyone tried the green hand-bendable NAPA lines?

 

[Scrounger]

Has anyone tried the green hand-bendable NAPA lines?

That is the only line that I use anymore.

 

[frank8003]

Poly-Armour® ................never heard of it until just now.
"Underneath the PVF-coating is a double-wall, low carbon steel, copper brazed tubing which meets all international and U.S. requirements for brake tubing"
https://www.youtube.com/watch?v=XADAMp4CswM

 

[topo]

Poly Armour is on E-Bay in 25 foot coils . I will try it.

 

[rustystud]

Has anyone tried the green hand-bendable NAPA lines?

I will not use any line that can rust.

 

[Robo McDuff]

If you have one line that has already cracked you'll have more. It's time to replace the whole system. Look at "Peashooters" lines he sells. Also his post will help you get any other lines you will need.

Ditto in spades. Quicker and cheaper to do everything in one go, including the flex lines. But first, change your Deuce to a dual brake system. Next time you will not have enough room for a slow brake - run out after a brake failure like that.

 

[icecreamman]

I have annealed both hard drawn copper and steel tubing for bending. Don't do it unless you have an idea about what you are doing.

 

[icecreamman]

I have hand built stuff to replace mandrel bent pieces from factory that were cracked. Blood bank refrigeration work is a little critical.

 

[cucvalbanese]

I am interested in this. What size would I get for a brake like 1/4 inch? Are they just a soft copper in which I would still flare?

I am referring to the napa lines.