Another brake question

[Houston Ben]

I put on new pads and drums on the rear end of my truck not to long ago and thought they were doing ok. I am in the middle of installing a true trac and had to remove the drums and noticed the pads have worn smooth on a few spots and the rest of the pad still looks new, does anyone know what could cause this??

The pads and drums are brand new and shouldn't be wearing this way should they??

Thanks for any help!

[Houston Ben]

update: I installed the true trac but something was making a bad squealing/squeaking noise so I jacked the back up and put the vehicle in drive do see if I could fined where it was coming from. When I stepping on the brakes I couldn't get the rear tires to stop, they slowed down but not stop!!!

Can anyone point me in the right direction on this pleas??

[walkerb]

Have you tried adjusting the adjustment wheel? This will move the pads closer to the drums

[Houston Ben]

Yes sir, I did. I had them tight on the drum but still nothing. The cylinders, pads, and drums are all new. When I push on the brakes there is some pushback while the peddle sinks about 2-3" then the brakes kick in??? Also, when I bleed them the fluid comes out fine, it doesn't shoot out but comes out pretty good.

BTW, thanks for the reply!!

[walkerb]

And they are bleed well?

[Tx Firefighter]

Back up and bleed them at the frame line where it connects to the rear brake hose. If it bleeds well there, but less at the wheel cylinders, suspect clogged hose internally.

[Houston Ben]

Thanks for the replies guys. Walker, I thought they were but I will have to check again. Kevin I will check that out for sure. Thanks for the help guys!

[walkerb]

No problem. Im pretty sure that's going to be the issue.

My sister lives down in Houston, I cant have you guys driving around with no brakes! haha

[walkerb]

And if you can it would hurt to bleed all four corners

[Lowl!f3]

Originally Posted by Tx Firefighter

Back up and bleed them at the frame line where it connects to the rear brake hose. If it bleeds well there, but less at the wheel cylinders, suspect clogged hose internally.

X2
Also the rubber hose can be collapsed inside. More or less creating a clog when pressing the brake. But enough to allow the pressure off the cylinder. if it was collapsed the other way. Your cylinder pressure will not drop and chew up the pads and or even lock up the hub.

[cool68]

another thing to try is having drums turned. some drum brakes have a front/rear shoe for each wheel.

[Oldriginal86]

Make sure the safety valve inside the proportioning valve is centered. This would reduce or completely stop pressure to build in rear system.

[Keith Seymore]

One other thing to consider, since this sounds like a recent rebuild:

The rear shoes are "ground" such that the contact patch starts in the center (both side-to-side and lengthwise) and then increases as the shoes are seated.

If the contact starts at the ends then you will get a chatter and noise; starting the wear in the center keeps them quiet while they are breaking in.

Perhaps it is too recent and they are not fully seated yet.

K

[Houston Ben]

Thanks for all the replies,
Ran into a snapfu last night. I had the drums off to look at my true trac so while they were off I had my wife push on the brakes. The driver side rear piston did not move at all and the passenger side moves a little and it took approximately 1/2" a second to do it, real slow like. As the pistons are new I guess I will be replacing the rubber brake lines. Also, how do you the safety valve inside the proportioning valve??

Thanks again!

[Keith Seymore]

Originally Posted by Houston Ben

Thanks for all the replies,
Ran into a snapfu last night. I had the drums off to look at my true trac so while they were off I had my wife push on the brakes. The driver side rear piston did not move at all and the passenger side moves a little and it took approximately 1/2" a second to do it, real slow like. As the pistons are new I guess I will be replacing the rubber brake lines. Also, how do you the safety valve inside the proportioning valve??

Thanks again!

...SNAFU...

Systems
Normal:
All
Frigged
Up

...only they didn't say "frigged".

K

[Tx Firefighter]

Originally Posted by Keith Seymore

One other thing to consider, since this sounds like a recent rebuild:

The rear shoes are "ground" such that the contact patch starts in the center (both side-to-side and lengthwise) and then increases as the shoes are seated.

If the contact starts at the ends then you will get a chatter and noise; starting the wear in the center keeps them quiet while they are breaking in.

Perhaps it is too recent and they are not fully seated yet.

K

Good tech there. Few people know or even think about the arc of a brake shoe.

Back in the day, many garages would "arc" your new shoes when they did a brake job. Its a dead art now though. There's a local shop here in town that still has a big old sign in the bay advertising the service. I'd like to buy their machine just for the novelty of it.

Google picture search....

[Keith Seymore]

Originally Posted by Tx Firefighter

Good tech there. Few people know or even think about the arc of a brake shoe.

Back in the day, many garages would "arc" your new shoes when they did a brake job. Its a dead art now though. There's a local shop here in town that still has a big old sign in the bay advertising the service. I'd like to buy their machine just for the novelty of it.

Thank you; naturally, we had a problem one time.

Presenting symptom was rear brake "moan" on the JB7 brake system. I spent quite a bit of time at a supplier called "Unibond" and learned a lot about rear shoes, production techniques and this "arc" process.

More than I wanted to -



It might seem trivial, since it looks like they are "right up the road" - but at the time I was resident at the Desert Proving Ground in Arizona, so it was quite a trip.

Still have their complementary note pad.

K

[Oldriginal86]

We used to grind the shoes to match the drum diameter years ago. Don't think the EPA or OSHA would approve now and there isn't asbestos in the brake parts anymore.
To reset the safety valve, need to determine if the valve is at fault. Is the brake warning light on? Does the brake warning light work?

[Houston Ben]

Na, brake warning light does not work. Ima pull the line off the piston and see if I can get any oil out of her tomorrow. So how do you reset the valve??

[Oldriginal86]

Once the pressure equalizes on both sides of the valve, the valve should center itself when the pedal is pressed to build 450psi in the system. With the light not working its difficult to tell what position it's in. Maybe the easy thing to do would be to replace it. The terminology they use in the GM manual is combination valve. It has 3 functions. If the light worked, you could see the position or issue with the system.

[Houston Ben]

Thanks for all the responses everyone. Today I was puting my true trac in and with the drums off I decided to stomp on my brake peddle just to see what would happen. Well, the drivers rear that was not working flared out big time. I put it back in place and put the drum and tire back on and took it out to test the true trac and the brakes worked awesome!!! no more spongy feeling or swooshing sound, it is awesome!!

Thanks all!