jsadamson1

Having trouble sourcing my brake failure.

Fluid full, brakes bled
Depress brakes and hold, all the sudden the pedal gives and hits floor and truck starts rolling. If I let go and depress again it will stop.....until it gives out again and the cycle continues.

Also brake light is on.

Thanks in advance

9812vram

Sounds like leakage past the master cylinder plunger. Time for rebuild/reman/new...

jsadamson1

So a master cylinder would possibly solve?

I went out and I can also hear air when I depress the brakes. Does that still point to a master cylinder?

Crossy's son

The woooosh of air you're hearing is probably the vacuum booster.

Sounds like replacing the Booster and the master cylinder with NEW units will fix the problem.

Be sure to get a NEW master cylinder, not reman. The reman ones they don't machine the top and the cap doesn't seal. New master cylinders work much better.

Exekiel69

Could be many things on a brake system, vacuum leak, bad booster, master cylinder and as in My case the abs/proportioning valve on the back of the truck I removed it and the brakes work great since then.

jsadamson1

Thanks for all the help. I will have to try out the new boost and master and see where I end up.

NJTman

Do a search on my threads.


All I can tell you is that you need to stay away from Napa's master cylinders. I replaced 3 NEW.... yes that's NEW master cylinders, and they all leaked out the cap.


I guess you could use one if you like having brake fluid remove all the paint off of your frame several times, as I did.

Bendix is the winner in my book.

kiszka6911

When I did my hydro boost conversion I used a Master cylinder from a 90's 1-ton chevy pickup with JB8 heavy duty brakes. Of course it was a bolt on to the chevy hydro boost even though the hydroboost was a older model. IMO hydro boost is the way to go on these trucks!

longshotranch

Here's a link for a hydro boost system

http://www.vancopbs.com/category_s/78.htm

jsadamson1

I think I am going to pass up any modifications to the dodge for now. I did however get a new master cylinder and booster installed. It's nice to be able to stop, literally. I do have one issue though, while I can stop now and when I hold the pedal down it doesn't sink lower, if I pump the brake once, the brakes seem to activate sooner than just hitting the pedal one time. I would rather have the quicker response but with out the pumping, any suggestions?

rebal

check rears for proper adjustment and double check you got all the air out

jsadamson1

I had a feeling that would be where to start. I have lubed up the rear fittings as I felt they were about to snap when trying to loosen them up. I plan to flush out the entire system with new fluid in case of contamination. I plan on pumping the old fluid through until it's clear so would you guys recommend starting in the rear or front for best results? Or does it matter?

rebal

start in the rear and do the rwal first then rr lr rf lf

Crossy's son

Yea do the valve on the frame first, usually when you get crappy brakes on 1st pump and good brakes on 2nd pump it means the rear RWAL valve is going bad and not allowing proper amount of fluid flow to the rear cylinders on first pump.

Usually when you bypass the Rwal valve you have a very high responsive brake pedal, but then lose rear ABS, very easy to lock up the brakes in crappy weather

Crossy's son

Have you done the rear brakes yet? Chances are they haven't been done in a while, probably contaminated in gear oil, probably not adjusted.

Buy the correct hub nut socket, pull the axle out & Bearings, pull the drum off and have a look see, remove the self adjusters and lube up the threads with never seize, If shoes are NOT contaminated and have meat left, throw them back together and adjust the rear brakes with the rear of the truck jacked up , adjust them so they barely drag.

Instructions for adjusting rear brakes can be found here, https://www.dieseltruckresource.com/...d.php?t=207170
makes a big difference in brake power and pedal feel.