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Unread 02-03-2013, 11:23 AM   #1
ZJMatt
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No brakes! No air in the lines, but acts like it.

Been at this same point for about 2 weeks now. It's the only thing stopping me from having my jeep on the road after the axle swap.

So, when swapping the axles, I forgot to pinch off the lines before disconnecting them. Master cylinder drained, ABS pump got filled with air.

Rather than paying an arm and a leg to have the dealership use their special machine to bleed the ABS pump, I connected the rear brake line to the back port on the proportioning valve, and made a T-junction off the front port to feed each front brake line. Essentially bypassing the ABS pump. In theory I should have great brakes now, just no ABS.

I've bled the brakes about 6 times now at the calipers, bled the master cylinder twice. Bled them at every fitting along the way. Also read that the proportining valve needs to be reset, which can be done by jabbing the brakes really hard. Tried that until my leg hurt.

At this point, I have straight fluid (no air) coming out of the bleeders at all 4 calipers. Master cylinder is full of fluid.

The first time I press the pedal, it goes almost to the floor, brake light comes on. If I pump it, I get brakes. Let it sit for a few seconds, no more brakes.

I'm stumped now... any ideas?

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Unread 02-03-2013, 02:21 PM   #2
melk
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Well the rear port on the prop valve is for the front line and it sounds like you hooked up the rear line to that one?

Prop valve has 2 ports for the front, 1 for the rear line which then gets split at the rear axle.

Look at this diagram:

Not sure if this will cure your problem but its probably best to have them hooked up properly.

I think the real issue is having had the master cylinder run dry. I'm no guru when it comes to brakes but from what I've read letting the MC go dry is a Bad Bad Thing. I'm not sure if its as simple as filling it back up.
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Unread 02-03-2013, 03:17 PM   #3
Mark05059
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you dont happen to have the calipers on upside down? Bleeder screws should be at the top.. just a suggestion.
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Unread 02-03-2013, 03:50 PM   #4
jtackerman28
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Quote:
Originally Posted by Mark05059
you dont happen to have the calipers on upside down? Bleeder screws should be at the top.. just a suggestion.
Been there done that haha
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Unread 02-03-2013, 04:17 PM   #5
Mark05059
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Quote:
Originally Posted by jtackerman28 View Post
Been there done that haha
I think everyone has once... but only ONCE
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Unread 02-03-2013, 08:04 PM   #6
ZJMatt
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Quote:
Originally Posted by melk View Post
Well the rear port on the prop valve is for the front line and it sounds like you hooked up the rear line to that one?

Prop valve has 2 ports for the front, 1 for the rear line which then gets split at the rear axle.

Look at this diagram:

Not sure if this will cure your problem but its probably best to have them hooked up properly.

I think the real issue is having had the master cylinder run dry. I'm no guru when it comes to brakes but from what I've read letting the MC go dry is a Bad Bad Thing. I'm not sure if its as simple as filling it back up.
A little confused by that diagram, but I'll try to make better sense of it while looking at the jeep tomorrow night.

Quote:
Originally Posted by Mark05059 View Post
you dont happen to have the calipers on upside down? Bleeder screws should be at the top.. just a suggestion.
I didn't touch the calipers (Except one rear, which yes is installed correctly). The others were on this axle when I got it, and the jeep it was in had good brakes before.
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Unread 02-03-2013, 10:31 PM   #7
AVR2
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A couple of things come to mind:

When the master cylinder ran dry, you really needed to pull it and bench-bleed it. Did you do that?

Even though air got into the ABS pump, you didn't need to mess with any of the brake lines. Assuming that you just don't want ABS, you can simply pull the ABS relay in the PDC under the hood. Bingo, no more ABS, and the fact that there's air inside the pump is irrelevant. You'll get the yellow warning lamp on the dash, but you can pull the bulb if it's distracting.

From what I know of the procedure for permanently bypassing/deleting the ABS, there's more to it than what you've done, but I could be wrong. Check out this thread for a write-up with pictures. There may be something there that helps you fix your problem.
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Unread 02-04-2013, 07:43 AM   #8
ZJMatt
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Quote:
Originally Posted by AVR2 View Post
A couple of things come to mind:

When the master cylinder ran dry, you really needed to pull it and bench-bleed it. Did you do that?

Even though air got into the ABS pump, you didn't need to mess with any of the brake lines. Assuming that you just don't want ABS, you can simply pull the ABS relay in the PDC under the hood. Bingo, no more ABS, and the fact that there's air inside the pump is irrelevant. You'll get the yellow warning lamp on the dash, but you can pull the bulb if it's distracting.

From what I know of the procedure for permanently bypassing/deleting the ABS, there's more to it than what you've done, but I could be wrong. Check out this thread for a write-up with pictures. There may be something there that helps you fix your problem.
No, We bled it in the vehicle by cracking the fittings on the lines.

How would that work? If there's air in the pump, and you don't bypass it, you're still going to be trying to pump fluid through the pump, even with the ABS off. The lines are routed to go through it.

That thread is prettymuch what I did.
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Unread 02-04-2013, 08:07 AM   #9
AVR2
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Quote:
Originally Posted by ZJMatt View Post
No, We bled it in the vehicle by cracking the fittings on the lines
As I understand it, if the master cylinder runs dry it really needs to be bench-bled, just as if you had a brand-new master cylinder. You do the bench bleed first, then you install it and bleed it at the fittings.

Quote:
How would that work? If there's air in the pump, and you don't bypass it, you're still going to be trying to pump fluid through the pump, even with the ABS off. The lines are routed to go through it
I may have misunderstood the way the system works, but I was under the impression that it's possible for air to be trapped within the HCU and not affect normal braking. When you do a dealership brake bleed with the DRB tool, it opens the solenoids inside the HCU (which normally stay closed unless the ABS is actuated) and runs the pump motor, which forces any air trapped in the valves into the brake lines, hence the need for another manual bleed.
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Unread 02-04-2013, 09:11 AM   #10
melk
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From your OP:

Quote:
I connected the rear brake line to the back port on the proportioning valve, and made a T-junction off the front port to feed each front brake line.
It sounds like you have this wrong as I previously stated. The "back" port, if we are talking about the same thing, is the one that is normally capped off when the HCU is hooked up. If you bypass the HCU and uncap that port, it is used for one of the front lines, not the rear. Double check the diagram. 2 ports for the front, 1 for the rear.
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Unread 02-04-2013, 10:16 AM   #11
ZJMatt
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Quote:
Originally Posted by melk View Post
From your OP:



It sounds like you have this wrong as I previously stated. The "back" port, if we are talking about the same thing, is the one that is normally capped off when the HCU is hooked up. If you bypass the HCU and uncap that port, it is used for one of the front lines, not the rear. Double check the diagram. 2 ports for the front, 1 for the rear.
So there is no need for the T junction? I didn't notice a third port. Then again I wasn't looking for one capped off. Haven't had a chance to look at it yet. I'm working til 10pm so probably tomorrow.
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Unread 02-04-2013, 10:22 AM   #12
melk
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Depends on your year. Some have the port and some don't. I'm not sure when the changeover was. My 96 looks like the diagram above.
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Unread 02-10-2013, 12:29 PM   #13
ZJMatt
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I hooked up the lines to the proportioning valve properly this time. Re-bled the brakes.

Still nothing! Pedal goes right to the floor when it's running. I have no time to work on this (notice it took me a week to swap fittings on 2 lines and bleed the brakes?) and a 1967 GTO sitting outside covered in 3ft of snow because the jeep is hogging the garage!

What I need is someone who will fix this crap in exchange for some beer. lol. I've been doing all my own work & upgrades since 16 but I get so frustrated when things don't work as planned.
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Unread 02-10-2013, 05:25 PM   #14
ZeeJay1997
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Quote:
Originally Posted by avr2 View Post
when the master cylinder ran dry, you really needed to pull it and bench-bleed it.
x2
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Unread 02-10-2013, 05:26 PM   #15
Pugulis
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Just a silly question. How's your vacuum pressure? Or more specifically is the check valve on the brake booster connected and working? I had a bad check valve on a car years ago and it did the same thing.
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