Author Topic: power brake booster  (Read 22425 times)

Offline Lt.Del

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power brake booster
« 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"

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

Edited by: SgtDel  at: 3/24/07 5:31 pm

Offline 77c15

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stupid fix
« Reply #1 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

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Offline Blazin

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Re: power brake booster
« Reply #2 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.

Some people are like Slinkies. Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs

Offline Lt.Del

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Re: stupid fix
« Reply #3 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

Offline Blazin

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Re: stupid fix
« Reply #4 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
Some people are like Slinkies. Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs

Offline Lt.Del

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Re: stupid fix
« Reply #5 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"

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

Edited by: SgtDel  at: 3/24/07 11:46 pm

Offline Lt.Del

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Re: stupid fix
« Reply #6 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

Offline Blazin

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Re: stupid fix
« Reply #7 on: March 25, 2007, 10:45:00 AM »
Get diamiter from drum ID.

Some people are like Slinkies. Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs

Offline Lt.Del

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Re: stupid fix
« Reply #8 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


Offline Blazin

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Re: stupid fix
« Reply #9 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.

Some people are like Slinkies. Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs

Offline Lt.Del

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Re: stupid fix
« Reply #10 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


Offline Blazin

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Re: stupid fix
« Reply #11 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?

Some people are like Slinkies. Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs

Offline roundedline

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Re: stupid fix
« Reply #12 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
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Offline Lt.Del

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Re: stupid fix
« Reply #13 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

Offline VileZambonie

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Boosters
« Reply #14 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.

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