73-87chevytrucks.com

73-87 Chevy _ GMC Trucks => Brakes, Frame, Steering & Suspension => Brakes and Braking Systems => Topic started by: Lt.Del on March 24, 2007, 05:57:00 pm

Title: power brake booster
Post by: Lt.Del on March 24, 2007, 05:57:00 pm: I'm having a little problem with my brakes on my 79 Big 10 383 th350 4bl. I have to put a lot of foot pressure do get these brakes to work decent. And when I do put a lot of pressure down, the brakes really clamp down and bring the truck to a stop quickly.

I have bled all the brakes and it doesnt help. I dont have a squishy pedal, just have to apply lots for force down.

I also hear a whooshing sound that is constant when I apply the brakes....like it is coming from the booster. I have good vacuum to the booster. When I apply, even gently, the brake pedal, I hear that whooooosh sound, not just for a second, but continuously as long as the brakes are applied.

I am wondering if my booster needs replacement. It's probably the original.

When I look at theAutozone chevy brakes website, it asks whether I have a JB3 or JB5 brake system. I have no idea. The part numbers are different depending on which I select.

To disconnet and remove the booster, do I have to get up under my dash and unhook the pedal or can I do all that from under the hood?

If I have to disconnect at the brake pedal, how does this rod disconnect?

Any ideas?
SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4
Edited by: SgtDel at: 3/24/07 5:31 pm
Title: stupid fix
Post by: 77c15 on March 24, 2007, 09:50:00 pm: This may sound weird, but I had the same problem with my dad's 79 Big Ten that I got him for fathers day. My buddy (ASE certified) recommended I change the little check valve and grommet that comes in a kit for the vaccum that goes to the brake booster. It's located on the "Help" brand aisle at Advance Auto Parts for just a couple of dollars. I kicked myself in the @#%$ when I realized what an easy fix it was, and your brake booster looks about in the same shape as his. Hope this helps!

-Mike
Title: Re: power brake booster
Post by: Blazin on March 24, 2007, 09:56:00 pm: If you have to swap it. the rod comes off the brake pedal arm with a couple 1/2 or 9/16 wrenches, a pair of needle nose to pull the pin. then it comes out with the booster.there are four nuts on the motor side of the firewall to remove it. You can lay the master off to the side so you won't have to bleed again. getting the sound deadener crap off is more work than getting the nuts off.
Title: Re: stupid fix
Post by: Lt.Del on March 24, 2007, 10:06:00 pm: Are you referring to this part (marked "A")?

I have no vacuum leak around it and unsure as to what it does. I sprayed wd40 around it and the rpms do not increase.

What is part "B"? What does that do?

SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4
Edited by: SgtDel at: 3/24/07 9:07 pm
Title: Re: stupid fix
Post by: Blazin on March 24, 2007, 10:10:00 pm: B is a check valve
I am in the chat room

Edited by: Blazin at: 3/24/07 9:10 pm
Title: Re: stupid fix
Post by: Lt.Del on March 25, 2007, 12:45:00 am: brake rod attaches to brake pedal here. I guess the key is on the other side which will allow the rod off the pedal rod?

SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4
Edited by: SgtDel at: 3/24/07 11:46 pm
Title: Re: stupid fix
Post by: Lt.Del on March 25, 2007, 10:17:00 am: How do you measure the rear brakes? On the link here

www. competitor.com/icatalog/cc/0148.asp

I am asked if i have 11'' or 11 5/32'' rear brakes for part #2, "F" or "H".

Edit: Woops. I see it now. There is a diagram up under the main pic that shows if Brake pads are 2" wide or 2 3/4" wide. i can firgure that out.
SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4
Edited by: SgtDel at: 3/25/07 9:20 am
Title: Re: stupid fix
Post by: Blazin on March 25, 2007, 10:45:00 am: Get diamiter from drum ID.
Title: Re: stupid fix
Post by: Lt.Del on March 26, 2007, 10:11:00 am: Well, it wasn't the check valve. I replaced that and the same problem exist.

Ordered the booster. I guess after 28 years, the rubber in the booster is pretty well dried up and cracked and unable to hold vacuum.

Time to get up under the dash and unhook the brake pedal rod from the pedal arm. Then separate the master cylinder from the old booster and remove the nuts holding the booster on the firewall.

This better solve the problem or you will see this truck in the for sale area.

by the way, i ordered the booster from Advanced and it is $99.00--less $15 for the core---so about $85. I should get it tomorrow.

I read up on how to check to see if booster works. You depress the pedal several times with engine off. Then turn on the engine, the pedal should fall about an inch. It doesnt.

I tried this too:

Shut engine off, place gear selector in neutral and pump pedal until all reserve vacuum in booster is depleted. Press and lightly hold brake pedal: if pedal doesn't hold pressure and falls away master cylinder is leaking internally. If pedal maintains pressure, start engine in neutral and if pedal falls away slightly then holds firm proceed to Booster Test Procedure. If no pedal action is noticed the Power Booster or Vacuum Check Valve is at fault.

On mine, the pedal didn't do anything after the engine was turned back on. No pedal action. Same thing after new check valve.

SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4
Title: Re: stupid fix
Post by: Blazin on March 26, 2007, 07:12:00 pm: I had one once that the pedal would very gradually go away if you held it for an extended period of time. It happened so slow you didn't even notice it until all of a suden the truck would roll. Pick up and restep on pedal it would stop. A budy of mine borrowed it and took my then girlfriend with him to pull an older woman, a friend of his's girl friend out of a snow bank. He was holding the brake, they got it hooked up and rready to pull. They let go and the truck rolled back and crashed into the car ( Escort ). It had a piece of 12" x 2" x 1/4" chanel iron for a rear bumper. It peeled the air filter right of the carb.
Title: Re: stupid fix
Post by: Lt.Del on March 26, 2007, 07:47:00 pm: Ouch!
That sounds like a master cylinder or air in lines when the pedal goes away gradually like that. I wished that were my case. Master cylinders are less expensive than boosters.

got that joker off tonight.

SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4
Title: Re: stupid fix
Post by: Blazin on March 27, 2007, 06:41:00 am: That was years ago when I was young. I thought it was the vacume booster, and swapped it out with a used one and it didn't do it anymore?
Title: Re: stupid fix
Post by: roundedline on March 27, 2007, 10:53:00 am: I sympothize with you SgtDel, I am going to have to do this to my Suburban tonight....
Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project
Title: Re: stupid fix
Post by: Lt.Del on March 27, 2007, 08:19:00 pm: Well, I like to follow Larry the Cable Guys advice.....

GitRDone

I got her done! It wasnt hard. You have to have the right 15 mm socket (yeah, i thought this was an American made vehicle)...one too small wont fit over the threads of the long bolts, one that is too long wont fit behind the booster with ratchet attached. My swivel wouldn't work too well either due to lack of clearance.

I found the perfect one at Advance auto. None of my previous numerous sockets worked.

The 9/16" nut on the brake pedal was easy...the bracket comes off and exposes the key that holds the booster rod.

The booster rod is a two piece. One end threaded into the other end...adjustable. I will have to extend the rod a little. The pedal goes a little over half way down before the brakes engage. I'll do that tomorrow...the main thing is, they work well!!!

The booster looks a little smaller than the factory one. I guess that is normal.

SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4
Edited by: SgtDel at: 3/27/07 7:22 pm
Title: Boosters
Post by: VileZambonie on March 27, 2007, 08:54:00 pm: SGTDEL They are different because you had a Tandem diaphragm booster and installed a single diaphragm booster.
Title: Re: Boosters
Post by: Lt.Del on March 27, 2007, 10:43:00 pm: Yeah, i noticed that after looking at the numbers. The salesman didnt know the difference. Of course, this was my first time doing it. Apparanently there is a booster for JB3 and for JB5 brakes. I think the JB5 was for the 2 3/4" rear brakes.

Two boosters

And wouldn't you know, I received the 5471108 part for two inch wide rear brakes. A 50 / 50 shot and the guy got it wrong. Live and Learn. This isn't exactly my specialty.

Oh well. Did I mention earlier that they work great?!?

It'll do for now. I don't think there is more power assist one way or the other.

SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4
Edited by: SgtDel at: 3/27/07 9:45 pm
Title: Re: power brake booster
Post by: 80stepsideguy on March 28, 2007, 01:17:00 pm: Heres a good question for some.I got a 85 cab that has a tandem diaphram booster on it but my 1980 had a single diaphram booster on it.I am going back to the 80 style truck setup but whats better for the tandem or the single?I kept the booster setup from the 80 cab i junked but if the tandem is better i`ll use it.
thanks
pat
Title: HD
Post by: VileZambonie on March 28, 2007, 01:30:00 pm: Tandem is for heavy duty brakes.
Title: quick dumb question...
Post by: 77c15 on March 28, 2007, 06:53:00 pm: If any of you guys have taken a look at the last page of my cardomain site, then you notices with the front end tore apart that I don't even have a power booster. Could I possibly put one on? Which one? I'd love to have power brakes, I just don't know which one will work. I think the holes are already there, just not sure what will bolt up. It's a 74. And by the way, Del, sorry the check valve was no help but at least you had one for the new booster or at least a spare. You never know when rubbers gonna fail.

www.cardomain.com/ride/788720/10

bottom pix on this page are good shots of the almost bare firewall. let me know what you guys think about how I can go about adding power brakes.
Title: Re: quick dumb question...
Post by: VileZambonie on March 28, 2007, 08:13:00 pm: Easy enough to do. Install the master and booster. The correct combination valve. Hook up the booster to manifold vacuum source and bleed the brakes.
Title: Re: quick dumb question...
Post by: Lt.Del on March 28, 2007, 10:29:00 pm: I like the way the six bolts are set up that keeps the booster on. You may wanna find some of those from a donor vehicle from the slavage yard, along with the other parts you'll need.

Those bolts, you'll see from my second pic on my first post, go through the firewall from the inside and are secure. It's better than the bolts spinning around--you can't be on both sides of the firewall at one time to tighten up the booster.

BTW, don't worry about the check valve advice. It was only $8. The new booster comes with the booster rod and check valve if you are interested in gettng one.
SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4