brake booster
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Posting Guru
Joined: Jun 2004
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From: Cincinnati Ohio
brake booster
How do you test for a bad brake booster? I am suspecting mine is bad.
My brakes are spongy. When your sitting still you can push the pedal down far then pump it up and the pedal gets hard. Is that suppose to be that way?
My brakes are spongy. When your sitting still you can push the pedal down far then pump it up and the pedal gets hard. Is that suppose to be that way?
Post Fiend
Joined: Jul 2004
Posts: 8,786
Likes: 28
From: Northern California
With the engine off, it is normal. Every time you press the pedal with the engine off it releases the stored up vacuum from the booster.
All the booster is for is to aid in pressing the brake pedal.
All the booster is for is to aid in pressing the brake pedal.
Posting Guru
Joined: Jun 2002
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From: Suffolk, VA USA
With the brake warning light issue and dirty fluid in your master cylinder, I strongly recommend you resolve those issues before you start on your master cylinder....spongy brakes can easily be related to those other two symptoms. You've got several different strings going, all running in circles around these symptoms. Resolve the obvious. If you check your proprtioning valve safety switch, as has been recommended to you several times now, you can narrow the focus greatly. The discolored fluid and spongy brakes only reinforces the need to do that check first. If disconnecting the switch turns the brake warning light off, you likely have a pressure problem somewhere downstream in the system. Likely a leaking wheel cylinder, or leaking brake line. Either of those will cause the fluid to discolor. You're getting good advice on here.
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Posting Guru
Joined: Jun 2004
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From: Cincinnati Ohio
This weekend were going to flush out the whole brake system. Actually I think I told you wrong its the resivor for the front brakes that are all dirty looking, we have never messed with the fronts, although the PO put on new brakes, and rubber hoses, and rotors.
Today I also noticed you can also push the brakes to the floor then keep pumping to pump them up to be stiff. Is that also normal with it running, or is there air in the lines? We inspected all the lines and there is no fluid seeping out anywhere.
Again thinks for the advise, and remember im not to knowledgeable about diesels yet.
Post Fiend
Joined: Jul 2004
Posts: 8,786
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From: Northern California
No that is certainly not normal at all.
If it's the front brakes that looks dirty, then it could be the calipers are leaking. Or you got a bad master cylinder. Or that there is ai or contaniments in the brake lines.
This is why your Brake warning light is on. you have brake faliure to one of the axles. I would guess the front, because of the discoloration of the fluid.
Flush the system with clean fluid, check it for leaks, etc...
Above all don't drive t untill the brakes are corrected.
If it's the front brakes that looks dirty, then it could be the calipers are leaking. Or you got a bad master cylinder. Or that there is ai or contaniments in the brake lines.
This is why your Brake warning light is on. you have brake faliure to one of the axles. I would guess the front, because of the discoloration of the fluid.
Flush the system with clean fluid, check it for leaks, etc...
Above all don't drive t untill the brakes are corrected.
Thread Starter
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Posting Guru
Joined: Jun 2004
Posts: 1,808
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From: Cincinnati Ohio
No that is certainly not normal at all.
If it's the front brakes that looks dirty, then it could be the calipers are leaking. Or you got a bad master cylinder. Or that there is ai or contaniments in the brake lines.
This is why your Brake warning light is on. you have brake faliure to one of the axles. I would guess the front, because of the discoloration of the fluid.
Flush the system with clean fluid, check it for leaks, etc...
Above all don't drive t untill the brakes are corrected.
If it's the front brakes that looks dirty, then it could be the calipers are leaking. Or you got a bad master cylinder. Or that there is ai or contaniments in the brake lines.
This is why your Brake warning light is on. you have brake faliure to one of the axles. I would guess the front, because of the discoloration of the fluid.
Flush the system with clean fluid, check it for leaks, etc...
Above all don't drive t untill the brakes are corrected.
Thanks 81f150, you've helped me a lot and appreciate it a lot.
I guess it calls for taking the front tires off now. Ive never messed with front brakes on it yet. I will in doubt check closely for leaking calipers or and spots in the lines. If I don't find anything Ill go out and get a new booster.
How would I go about getting contaminants out of the lines? or would replacement lines be on order?
I don't plan on getting it on the road yet, All we ever do is when we work on it is drive it up the road to check things and thats about it.
Thanks again
Super Moderator
Joined: Apr 2004
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Fluid gets contaminated in the calipers and wheel cylinders, as regardless of the condition of seals, there is some introduction of air and/or moisture to the system through the seals and movement of the parts.
Flushing the system while bleeding the system will get rid of the contaminated fluid and any air as well.
You can usually bleed without pulling wheels, but if you need to inspect wheel cylinders, you have no choice. Some calipers can be seen clearly enough w/o removing wheels.
Flushing the system while bleeding the system will get rid of the contaminated fluid and any air as well.
You can usually bleed without pulling wheels, but if you need to inspect wheel cylinders, you have no choice. Some calipers can be seen clearly enough w/o removing wheels.
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Posting Guru
Joined: Jun 2002
Posts: 2,091
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From: Suffolk, VA USA
What I was trying to say was don't worry about the brake booster now...not the master cylinder...guess that's what I get for trying to write at 6 in the morning....sorry about the confusion.
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From: Virginia
Today I also noticed you can also push the brakes to the floor then keep pumping to pump them up to be stiff.
