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Discussion Starter · #1 ·




i got my insurance card from Robbin today (e-mail so i could drive right away.)

i took the car out for 40 miles. i 'rode the brake' down big hills, stomped on it, everything i could think of. i even let the car roll backwards down and hill and hit the brakes.

my last master was a stepped one plumbed backwards. i put that right, and the braking is much improved. the feel of the pedal is much better. now that i have the "straight" adjustable brake rod from Breeze the brake pedal is more even with the clutch pedal (top height), and it does not "bounce" past the top. it also does not make a creaking noise, we learned that because the old pushrod was rubbing something.

the problem is that the brake pedal is still "sometimes faded." every 15 minutes or so, it will go 3/4 of the way down with nothing. not that i would really do that, if the pedal is "pre faded" as i call it, all i need to do is pump it again and it's ROCK solid from all the way up top.

most the time it's soft for 1" of travel or so and BAM they are rock solid. if i pump it twice, the second pump would be solid from all the way up top. the 1" of travel is identical to the free-play in my clutch pedal.

i bled the brakes all around more times than i could count, and i saw absolutely no bubbles coming out anywhere. all of the old fluid was pushed out, because all the new fluid going to the catch bottle eventually came out crystal clear. we went through two full bottles of brake fluid.

recently on TV... i don't remember which car show, but it's the one with the 'Larry the Cable Guy" sounding guy... they used a reverse bleeder. there are also youtube videos for it.

Harbor Freight has one for $27, Phoenix has one for $350.

advice?
 

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Hate to tell you this, Eddie, but you still have some air trapped somewhere. Probably in the m/c.
 

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Self adjusters?

When brake pads are initially changed the caliper pistons are pushed into the caliper as part of the process. The first time you hit the brake pedal it will travel all the way to the floor as it moves the piston out to contact the pads and rotor. It retracts slightly to release the brakes, but doesn't return completely into the caliper. The next time you hit the brakes the piston has to move only a short distance so the pedal travel is also short. I wonder if the self adjusting mechanism on one of your calipers has a problem. I believe you have an unusual caliper on the rear that has opposing pistons. I'd look at those first.

Jeff
 

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Since you already have everything on the car, and I recall that you have the tools to make new brake lines, you can bleed the master cylinder on the car. You'll just need to build two new brake lines, plumb them back into the reservoir and pump the brakes until no more bubbles form. Here is a picture from an old Toyota:

 

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Discussion Starter · #6 ·
yes, i bench-bled the master cylinder.

i thought about what Jeff said. since the problem is exactly the same as before, maybe there is something wrong with one of my calipers.

i have Wilwood rear and stock mustang front.

.
 

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Reverse bleeding is the only way to go in 2012. You'll do it once and be done. The old fashioned way goes against the laws of physics as air likes to go up. So pushing the air up rather than attempting to push it down makes the job easy. Think about how difficult it is to try to push a ballon filled with air down in a pool. Very frustrating. I used the Phoenix. The HF one is...let's just say...you'll wish you had saved that $27 for lunch. I'd also suggest a NEW good old fashioned Jeep MC like you had before. Those Dorman MCs are harder to bleed. I have two of them.
 

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Hunter, would that tool work in place of bench bleeding? How satisfied are you with the tool?
 

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What year Mustang fronts do you have? Any chance they are PBR's and swapped left for right? I seem to remember an issue where you could swap them and get an air bubble in the caliper.

-Scott

yes, i bench-bled the master cylinder.

i thought about what Jeff said. since the problem is exactly the same as before, maybe there is something wrong with one of my calipers.

i have Wilwood rear and stock mustang front.

.
 

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What year Mustang fronts do you have? Any chance they are PBR's and swapped left for right? I seem to remember an issue where you could swap them and get an air bubble in the caliper.

-Scott
I the calipers are reversed the bleeder will be at the lowest portion of the caliper hence not letting the air out as it would rise to the top section.
 

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In my experience air trapped in the lines doesn't just show up once every 15 minutes. The mushy pedal would be pretty constant. I wonder about axle endplay pushing the pistons back in the solidly mounted Wilwoods. That might be something that would show up intermittently depending on how much and how hard the car has been cornering prior to a given brake application..
 

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Get yourself one of these: Phoenix Systems reverse bleeder http://www.summitracing.com/parts/PSL-2004/



I just replaced my master cylinder with a Wilwood dual setup. I "bench" bled the master cylinders in the car and bled the whole system in about 15 minutes. I'll never go back to the old way of bleeding brakes.

Pete
 

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Agreed - air doesn't just come and go. Factory calipers are mounted on pins or guideways machined into the mount, and float to stay centered on the rotor.

BUT - Wilwood and other competition calipers are rigid, and the complementary rotor is mounted on pins to float. It uses a special hub to do that.

Something has to float, your choice.
 

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Discussion Starter · #14 ·
hmmmm. more complicated than i thought, now axle play may be a problem.

out of fear of complications, brakes on DD's are pretty much the only thing i pay Pep Boys to do, but when the brakes go on my Tacoma in about a year, i plan to try it myself.

so a quality bleeder tool will be worth the investment.

another 150 mile drive last night, same results. just once the brakes were faded (3/4 way down and no pressure) - then the second quick pump and they were rock solid. i didn't even need to let the brake pedal get back to the top, just a wee up and BAM they are rock solid.

there is also a mysterious "leak", it's getting moist around the lip on the plastic reservoir. we are talking 2ml spread over the front part of the lip. the fittings are bone dry, and it does not seem to be leaking out the cap. at first, it was a wee over-fill, but i took some fluid out.

.
 

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eddie, i just purchased one of those bleeders the other day after reading this thread. Should be here next week. Your welcome to try before you buy if you want.
 

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I still believe you have a piston in one of your calipers that is being pushed back into the housing. I believe you just converted from rear drum to rear disc brakes. I suspect the problem is in the rear if this just started since the conversion. Look over the installation closely.

Jeff
 

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Discussion Starter · #17 ·
QSL: i planned to spend even a few more bucks on a higher quality unit that came with a case. we'll see how yours works out. :)

i will have to read about how to investigate my rear brake calipers locking.

could this in any way be related to parking brake tension?
 

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Axle end play (post #11?)

Eddie,

With your 5 link rear end, is there a chance that you pulled the axles out during your brake conversion?

Any chance you left out a "C" clip holding the axle in?

Once all bolted up (without a C-clip) the fact that the disk is captive by the caliper, you would have excessive free play pushing your caliper pistons back, causing a first press of the brake pedal condition not too far off of what you are describing here.

The axle would be floating back and forth as far as the caliper would allow it to, making it necessary for you to press the pedal twice to refill the piston reservoirs in the rear calipers, before there was disk pad movement sufficient enough to apply braking force.

Just a thought . . .

HTH

Doc :beerchug:
 

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Sounds like pad knock back, where fixed (not sliding) rear calipers aren't able to reset pad position relative to the caliper piston and rotor. If your rear rotors aren't perfectly flat or (more likely) you have some axle end play, it can create a small gap between pads and rotor face as the pads get knocked back towards the (fixed) caliper piston causing a noticeable irregularity in brake response.

Not an expert, so I'm not saying this is what it is, only that it sounds like pad knock back.

I think Sanford has similar rear brakes and he has used 'helper springs' to minimize it. Might try contacting him.

Sean



Sent from my Autoguide iPhone app
 
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