Need help air is getting in my brakes! (Updated) - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 04-13-2003, 04:15 PM Thread Starter
 
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Need help air is getting in my brakes! (Updated)

This is the deal with my brakes. 4 months ago I started driving after a complete frame off. Here is everything i replaced in the braking system: New calipers, pads, discs, stainless flex hoses, all new hard lines (preflared autoparts store lines, bent to fit my me), adjustable proportioning valve, drums, shoes, drum hardware, and wheel cylinders. The MC and power booster were new to me but not new. I got, or seemed to get, all the air out of the system 4 months ago, and had a very firm brake pedal for a while.

Now i have air in system. I have to pump before every stop or i get nothin, which probably means i have a lot of air in the brakes. I have tried to bleed them twice already. Both times i got a little air out, but not much. I have tried pumping and gravity bleeding.

Two questions: One, where is this air coming from? I have examined every inch of the lines and i can not find any fluid leaking out. Two, why can't i get all the air out? What is a good length of time to gravity bleed the brakes for? Thanks for your time, it is appreciated as always ~ Tim
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post #2 of (permalink) Old 04-13-2003, 05:02 PM
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Re: Need help finding how air is getting in my brakes!

I had a similar experience. I went to a professional that I trust and had him bleed the brakes. Turns out that I didn't have air in the lines but a faulty valve in the master cylinder. $100 bones later I was as good as new. I never lost much of any fluid if that matters to you. Let us know what it is when you find the problem. Good luck!
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post #3 of (permalink) Old 04-13-2003, 05:03 PM
 
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Re: Need help finding how air is getting in my brakes!

Sounds like a power booster issue to me
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post #4 of (permalink) Old 04-13-2003, 05:04 PM
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Re: Need help finding how air is getting in my brakes!

Change the master, its probably sucking air.
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post #5 of (permalink) Old 04-13-2003, 05:53 PM Thread Starter
 
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Re: Need help finding how air is getting in my brakes!

The proportioning valve is band new tho.

How whould i check the booster?

And what do i look for if the master is bad?

Thanks- Tim
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post #6 of (permalink) Old 04-13-2003, 06:01 PM
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Re: Need help finding how air is getting in my brakes!

</font><blockquote><font class="small">In reply to:</font><hr />
And what do i look for if the master is bad?


[/ QUOTE ]

I personally look for a brake shop. They will usually tell you what is wrong for free if you ask nicely. Then, if you want to fix it yourself, tell them you can't afford to fix it right now. I usually let them fix brakes, not something I want to chance.
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post #7 of (permalink) Old 04-13-2003, 06:15 PM
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Re: Need help finding how air is getting in my bra

</font><blockquote><font class="small">In reply to:</font><hr />
What is a good length of time to gravity bleed the brakes for?

[/ QUOTE ]

my rule of thumb is a samwich and two beers. or rootbeers depending on personal preference [img]images/graemlins/wink.gif[/img]

sound like something in master cylender or proportioning valve not holding residual pressure.

have you tried those new speed bleeder screws? they have a check valve in them and make bleeding way easy according to claims. i want to hear someone whos tried them if they are good or not.
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post #8 of (permalink) Old 04-13-2003, 11:01 PM
 
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Re: Need help finding how air is getting in my brakes!

After you pump the brakes do you get a firm pedal or is it spongy?
Does the pedal get hard if you pump it up and hold it down then slowly drop to the floor with the engine off? (try this a few times with lots of pressure on the pedal.)
Does the fluid level drop at all or does it stay full?

My guess is you have a bad master especially if it fades slowly to the floor or if the fluid level doesn't drop. For air to get in fluid has to come out.
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post #9 of (permalink) Old 04-14-2003, 12:48 AM
 
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Re: Need help finding how air is getting in my brakes!

You don't say what your working on but I suspect you either need a residual valve in the drum brake line(rear I assume) or you need expander cups in you wheel cylinders, or both. Get a shop manual so you know what your supposed to have...09
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post #10 of (permalink) Old 04-14-2003, 01:36 PM Thread Starter
 
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Re: Need help finding how air is getting in my brakes!

I am working on a 78 CJ5, PB, 6 bolt calipers.

in2mud- When i pump the brakes hard, with the engine off the pedal firms up a little. That is the pedal is still soft for the first half of the push and then firms up towards the end. As soon as i release the pedal by taking my foot off, all built up pressure from the pumping goes away and the pedal immediatly becomes soft again. The pedal has never physically dropped to the floor. Although i have been able to push it all the way to the floor without any resistance.

As far as i can tell the fluid level stays full.

Thanks for your help.
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