my abs and brake lights are both always on.

with the truck running, i will come to a stop, and while sitting at a stop, the brake pedal will slowly lose pressure and steadily creep its way closer and closer to the floor, until it is rock hard (like there is no fluid).

if i am stopped on a hill, the truck will actually start to roll, unless i press harder on the brake as it bleeds off.

i feel it is somewhat of a safety issue, and its been bothering me for quite some time.

master cylinder is full of fluid, and does not leak.

master cylinder and brake booster were both replaced by the previous owner not that long ago because i found reciepts.

are there any abs components that may have failed and are causing this problem? (linking it to the lights on my dash)

love to hear what you guys think

-Sean

 

Check to see what vacuum the vacuum pump is pulling first (should be near 20).


1. leaks in wheel cylinders in back brakes
2. internal leak in master cyl, esp if it was a reman. Get a new bendix or wagner off of rockauto
3. prior owner didn't bleed MC properly/ancient brake fluid saturated with water/air still in system

when is the last time the rears were adjusted?

 

I went through 3 "remanufactured" masters that all leaked internally. I bought a new one and it worked

 

were you experiencing the symptoms i described with a master cylinder that leaked internally?

 

^^^^^^^^^^^^^^ THIS!

I have gotten to the point where I won't even put on a reman unless a new one is not available, then I always drag out the lucky rabbits foot and have the Priest bless it before I install it.

And yea, your symptoms are classic internal bypassing.

 

Light can be as simple as Vaccum switch bad, or unplugged......

 

okay. so my brake fluid level never goes down though... so its leaking internally, but its not going anywhere?

what exactly is going on in there!?

if i gotta go to rockauto and get a fresh one, i will. just curious as to what is taking place.

 

Get a new MC. Make sure you use the correct brake fluid.

Sent from my DROID RAZR using Tapatalk

 

One possibility is that the ABS dump valve is bleeding fluid into the accumulator. There is a thread on by-passing it. Try the bypass method and if it doesn't fix the problem. then MC is bad...Mark

 

Sounds like an internal leak.

You are correct,
This is definatly a safety issue.
Stopping and steering should always have top priorty.

 

Before you do anything, read this:

https://www.dieseltruckresource.com/...8&postcount=11


I went through hell and back to get my brakes to work right. Since I now only use my special homemade gizmo, and a helping foot to pump the brakes, I've not had any issues since (except for freezing e brake cables).

I used a NEW Bendix master, and will never use anything other than it. Reman napa, new napa, and other remans. All leaked. All had a master brake fluid reservoir cap that leaked all over the truck. Never again. This bendix unit was the ONLY ONE that didn't leak out the cap.

 

Alright everyone I've taken your advice and read up on the links ou be included as well as the thread about "junking ABS" and this is what I'm going to do.

I just ordered the bendix 11775 MC. I will replace that and then bleed the **** out of the rear brakes and return with an update. Will probably take a couple weeks.

Thanks
Sean

 

Wow, I must have been really ahead of my time, I always used a mason jar with a hole in the lid for the hose to pass, with the end of the hose held below the level of the fluid.
I was at my parents house last month and the bleeding jar is still in the garage where I had left it back in the late 60's and my sister says she still uses it when she does brake jobs on her cars and for friends.

Good brake bleeding is a 2 person job, one pushes the pedel and the other opens the bleed screw and then closes it while the pedal is still in the down position or it will suck air back into the system, also be careful not to open the bleed screw too far or it will suck air.

I would also use a short hose on the bleed screw with a check valve inline if I absolutely had to do it by myself but a true pressure bleed is the best where it is flushed with about a quart of fluid.

Make sure to always use fresh fluid from a sealed can.
Be sure your front calipers are installed correctly, improperly the bleed screw will end up on the bottom of the caliper and it will be impossible to remove the air.

Jim

 

This is the method I have used for bleedin as well. Big jar so you can get it all done without have to pour it out every two pumps I the pedal

 

There is a primary piston and a secondary piston in the bore that your linkage presses on. The piston has rubber seals that seal to the bore, when they are sealing perfect you get a leak. Either a secondary or primary leak will cause the pedal to keep creeping down as you push. Loosing brakes on one circuit (front or back). If both circuits leak you loose the brakes front and back.

I would bypass your abs valve as well as replace the MC