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BJ8 Brakes

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mmotors

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Ok have a BJ8. Had the brake booster, master cylinder, and front calipers rebuilt by Apple Hydraulics. New rear wheel cylinders, new hoses (3), new brake shoes, and new brake pads. Cleaned the drums and rotors with brake clean prior to installing shoes/ pads. Bled brakes and had a good stiff pedal- as should be. Can notice a change in idle speed when brakes are applied (booster working). Did everything right, right?

The brakes require too much pressure to stop. Doesn't seem like a lot of grab. Can be locked up but with good amount of effort. Also rear axle seals are good- no leaks, and no grease from the ft seals. What could be the issue? Any ideas??????????? Help? Anyone had this issue before?
 
Hi mmotors, as a general rule if the brakes require an abnormal amount of pressure to operate the brake booster is not operating correctly. While this is not surprising to me some vendors have a hit and miss reputation. The only check I can think of is to bypass the booster and see if pedal pressure and brake operation remains the same.---Keoke
 
Don't worry about apples. Do what Keoke says and bypass the booster. If your pedal doesn't change, call the vendor and ask them to assist in diagnosing the problem.

Cheers
T
 
anthony7777 said:
keoke, i think perhaps a re-blead first?--but you may have hit on something..the word apple,.. oh boy here we go! :thumbsup:
Click to expand...

Well yeah 7777's , but he mentioned he also notices a change in idle speed when the brakes are applied, which suggested that a vacuum leak is being generated some place. Thee only thing using vacuum in the brake system I could think of is the booster.????--Keoke
 
mmotors -

The brake booster on the BJ8, when working properly, provides a great deal of boost - it actually gives a fairly soft pedal.

It sounds to me that Apple did not rebuild the booster correctly, which is not a surprise. The boosters are very finicky, and require very special treatment to be rebuilt... simply replacing the rubber seals is not enough.

There are little valves in the booster, which I suspect that Apple did not replace. (British Car Specialists in Stockton have these.) If these little valves are not working - you won't get any boost and your idle will increase a bit when you step on the brakes.

NOTE: if your idle increases when you step on the brakes, this is an indication that your booster IS NOT WORKING CORRECTLY. either send it back to Apple to have them fix, or ask for a full refund and then send the booster to White Post for a proper rebuild and test:

https://www.whitepost.com/brake.html
 
Glad this topic came up again, rebuilt my booster last fall. Good pedal, if I push hard on brakes, brakes lock up big time. Let the car set for a couple of hours and it rolls easy. I tried bleeding pressure off at master cyl to see if it was MC holding pressure but no pressure there. Will try Keoke's suggestion of by passing the booster.
 
mmotors said:
Do you think pulling the vac line a plug the manifold be be suffient to check?
Click to expand...


:savewave:--NO! Keoke
 
Marvin Gruber said:
Glad this topic came up again, rebuilt my booster last fall. Good pedal, if I push hard on brakes, brakes lock up big time. Let the car set for a couple of hours and it rolls easy. I tried bleeding pressure off at master cyl to see if it was MC holding pressure but no pressure there. Will try Keoke's suggestion of by passing the booster.
Click to expand...

Marvin -

The brakes are locking up because when you rebuilt your booster, you did not cut the rubber seal that fits under the leather seal in half.

Take your booster out and take the rubber seal out and cut off 1/3 to 1/2 the thickness and reinstall, this will fix the brakes locking up.

The leather seal only needs a small amount of pressure on it to seal properly.
 
Will be giving that a try, it sure can't hurt anything. I was just about ready to order new one. Now if I had the trafficator working?

That will be another story.

Thanks

Marv
 
A simple and effective test for brake boosters is to step hard on the brake pedal when you start the car. If, when the engine fires you feel the pedal go down an inch or so the booster is (likely) working.

My BJ8's booster works fine, but the pedal is still harder than any "modern" boosted brakes I've driven (and I'm running silicone BF, supposedly notorious for "soft pedal syndrome").
 
Marvin Gruber said:
Glad this topic came up again, rebuilt my booster last fall. Good pedal, if I push hard on brakes, brakes lock up big time. Let the car set for a couple of hours and it rolls easy. I tried bleeding pressure off at master cyl to see if it was MC holding pressure but no pressure there. Will try Keoke's suggestion of by passing the booster.
Click to expand...
Hi Marvin,
What was the problem that prompted you to rebuild the booster? Next question would be how old are the flex lines in the brake system? One to each front brake and one at the rear axle. Sometimes those old lines deteriorate on the inside and become valves.
 
Greg,

Actually I just finished a full year restoration of the car. My father had disassembled it years ago. Sandblasted tub, new floors, rockers and up. Booster was in a box. It did look pretty good inside when I went thru it. The rest of brake system is new (hoses, lines, master and slave). I can hear a brake booster noise when I step on the brakes.
 
Wish it was the hoses. I put the booster in while the shroud was off and engine out. I have another car on the lift right now but as soon as I'm done with it, the 3000 goes up.
 
Marvin Gruber said:
Wish it was the hoses. I put the booster in while the shroud was off and engine out. I have another car on the lift right now but as soon as I'm done with it, the 3000 goes up.
Click to expand...

Marvin -

To get the booster out, you can actually just reach up under the right fender with your right hand with a socket wrench and remove the booster without having to put the car on a lift... it's quite easy to get under there, just you'll have to work by feel.
 
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