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Old 05-20-2013, 06:26 PM   #1
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Spongy Brake peddle

Last week I replaced all the hard lines in my 2000 TJ with stainless steel lines because the OEM lines rusted through. While I was at it I also replaced the master cylinder, rebuilt the calipers (4) and replaced the proportioning valve because I did away with the ABS pump assy.

I bench bled the MC until I saw no air bubbles prior to installing it. Hooked everything up, gravity bled the lines until fluid starting coming out and then bled the system using a Mityvac pump. After bleeding the system I still had a spongy peddle, so thinking I still may have some air in the system I decided to bleed the system again using the old tried and true method of 2 person bleed.

Well long story short, I put about 2 quarts of fluid through the system could see no signs of bubbles anywhere from the calipers yet after all that I still have a rather spongy peddle.

Any thoughts as to what might be the issue? I know most of you will say still has air in the lines but like I said after 2 quarts of fluid being pumped through I didn’t see any signs of bubbles in the lines.

Any help would be appreciated.

Bill

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Old 05-20-2013, 06:49 PM   #2
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Did you install the calipers correctly with the bleeder valves pointed up? When I received my new rear axle the calipers were installed upside down because the builder swapped sides on accident. I couldn't successfully bleed the brakes until move each caliper to its original axle shaft.

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Old 05-24-2013, 07:47 PM   #3
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Yes they are in the correct location = On top
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Old 05-24-2013, 08:20 PM   #4
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1) Did you replace the caliper hoses also?
2) The replacement 'stainless steel lines', are they 'hardlines' or 'braided flex (hose)'?
3) The deletion of the ABS, did that create a 'high spot' in the lines, whereby air might be trapped?

[and for what it's worth, I personally think you're already on the correct diagnosis with it being air still trapped in the system]
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Old 05-24-2013, 08:29 PM   #5
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One more thing to go along with the above, have a look at your proportioning valve. Is the pin sticking out at the end ( wish I had a picture sorry ) sometimes while bleeding a complete system the proportioning valve will shift and not allow you to fully bleed one end.
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Old 05-24-2013, 09:11 PM   #6
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Quote:
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One more thing to go along with the above, have a look at your proportioning valve. Is the pin sticking out at the end ( wish I had a picture sorry ) sometimes while bleeding a complete system the proportioning valve will shift and not allow you to fully bleed one end.

You are correct in every aspect except for the pin part. Ours don't have them. The small hex at the front of the combo valve that has the rubber cap on it actually houses the front to back proportioning valve.

The shuttle valve inserts from the other end and has no way to move a pin for an external indicator that it is shifted.

What does happen is when it is shifted, the brake light on the dash turns on to tell you there is a problem.
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Old 05-24-2013, 09:18 PM   #7
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Thanks for clarifying that BMB I honestly havent looked on that system.

BTW I'm extremely happy with the rotors and pads still determining which route I'm going to go on the rear, keep the 44 and add disc or go 8.8 with disc.
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Old 05-24-2013, 10:17 PM   #8
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Thanks for clarifying that BMB I honestly havent looked on that system.

BTW I'm extremely happy with the rotors and pads still determining which route I'm going to go on the rear, keep the 44 and add disc or go 8.8 with disc.
Well, if you find a cheap 8.8 that someone stole the backing plates off of, we have both, 8.8 and 44 conversions.

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