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Unread 12-04-2010, 11:11 AM   #1
yarmish
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Brake bleeding questions,Spongy pedal

Ok so here is my situation:

Swapped in a new front axle with new calipers,Bake hoses and a driver side brake line from the master cylinder.

The calipers are mid 70's dana 44 calipers as are the hoses. Have bled the calipers at all 4 wheels with a good stream on each. "2 man bleeding" I still have a spongey pedal. Now at one point during the axle install my fluid resevoir was empty so it is pretty accurate that i have some air in my lines from the master cylinder back?

The pedal is nice and tight untill i turn the jeep on and then i get a soft pedal and bad brake performance.

So should we just keep bleeding all 4 calipers?

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Unread 12-04-2010, 11:31 AM   #2
TheMusicMan
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Please explain your bleeding technique. Letting us know exactly what and how you and the other person are bleeding the brakes.
Also where is the bleed nipple? it is very important that the bleed nipple be ontop of the caliper (as high on the caliper as possible. But definately above the brake line input). It is very easy to put the calipers on the wrong side and have the bleed nipple at the bottom trapping air.

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Unread 12-04-2010, 11:34 AM   #3
yarmish
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Quote:
Originally Posted by TheMusicMan View Post
Please explain your bleeding technique. Letting us know exactly what and how you and the other person are bleeding the brakes.
Also where is the bleed nipple? it is very important that the bleed nipple be ontop of the caliper (as high as possible. But definately above the brake line input). It is very easy to put the calipers on the wrong side and have the bleed nipple at the bottom trapping air.

TheMusicMan.
The bleeders are at the highest point of the caliper...learned that lesson watching a buddy of mine years ago.

The blleding technique used was one man on the bleeder and the other in the jeep. Pump up pressure on the pedal,i open the bleeder and watch the stream.

When the pedal is to the floor i close the bleeder and then the pedal is released. Repeat several times and keep the MC full.

Do you think i need to bleed the master if it was empty at one point during the axle swap?

Thanks alot
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Unread 12-04-2010, 11:39 AM   #4
TriCityAuto
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possibly a bad brake booster?
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Unread 12-04-2010, 11:53 AM   #5
garybattles
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Are you starting at the wheel furthest from the MC, rear passenger, then going rear driver, front passenger and finishing at the front driver? Don't know about the MC.
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Unread 12-04-2010, 11:56 AM   #6
mrblaine
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Quote:
Originally Posted by yarmish View Post
The bleeders are at the highest point of the caliper...learned that lesson watching a buddy of mine years ago.

The blleding technique used was one man on the bleeder and the other in the jeep. Pump up pressure on the pedal,i open the bleeder and watch the stream.

When the pedal is to the floor i close the bleeder and then the pedal is released. Repeat several times and keep the MC full.

Do you think i need to bleed the master if it was empty at one point during the axle swap?

Thanks alot
Several things, your bleeding technique is aerating the brake fluid.

In this order-
Open bleed screw, say down
Helper pushes pedal down fast with enthusiasm and when the pedal is down, says down.
You close bleeder and say up
When the pedal is up, helper says up.

You open bleed screw and say down. Rinse and repeat 4 -6 times per caliper.

If it takes more than two rounds of that, stop and find the problem because all you're doing after that is wasting time and fluid.

If your master ever went dry, remove it and bench bleed it. Get the plastic plugs that fits the ports and install them. Clamp the master in a vise with the ports plugged and the master level. Fill half to three quarters full of brake fluid and start stroking the plunger. Start with short strokes and increase to repeated full strokes until you can only depress the plunger 1/8" to slightly less or so.

Install master back into the rig, remove the plugs one at a time to hook up the lines to the combo valve. No muss, no fuss.

Then do your bleeding again.

A side note- please double check to make sure your bleed screws are oriented correctly. I know you said you checked, but a pedal that goes to the floor after starting the motor is a classic symptom of bleeders on the bottom.
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Unread 12-04-2010, 12:06 PM   #7
yarmish
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Quote:
Originally Posted by mrblaine View Post
Several things, your bleeding technique is aerating the brake fluid.

In this order-
Open bleed screw, say down
Helper pushes pedal down fast with enthusiasm and when the pedal is down, says down.
You close bleeder and say up
When the pedal is up, helper says up.

You open bleed screw and say down. Rinse and repeat 4 -6 times per caliper.

If it takes more than two rounds of that, stop and find the problem because all you're doing after that is wasting time and fluid.

If your master ever went dry, remove it and bench bleed it. Get the plastic plugs that fits the ports and install them. Clamp the master in a vise with the ports plugged and the master level. Fill half to three quarters full of brake fluid and start stroking the plunger. Start with short strokes and increase to repeated full strokes until you can only depress the plunger 1/8" to slightly less or so.

Install master back into the rig, remove the plugs one at a time to hook up the lines to the combo valve. No muss, no fuss.

Then do your bleeding again.

A side note- please double check to make sure your bleed screws are oriented correctly. I know you said you checked, but a pedal that goes to the floor after starting the motor is a classic symptom of bleeders on the bottom.
I was hoping you would answer this thread for me I will do exactly as you say. I will start with bench bleeding the master and then bleed the calipers. I will post up my results.

Thank you
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Unread 12-04-2010, 01:28 PM   #8
travisrda
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brake bleeding

one thing you need to make sure of is that the calipers slide freely and are not frozen on the slide bolts otherwise you will never get them to work right. amhik
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Unread 12-04-2010, 02:58 PM   #9
BlueFlame
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I would also not reuse the 1970's brake lines (I assume you mean the flex lines.)
They could be soft and are ballooning.
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Unread 12-04-2010, 05:45 PM   #10
yarmish
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Quote:
Originally Posted by BlueFlame View Post
I would also not reuse the 1970's brake lines (I assume you mean the flex lines.)
They could be soft and are ballooning.
Yes the flex lines I should of mentioned that it is all brand new as well
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Unread 12-04-2010, 06:19 PM   #11
travisrda
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if the calipers are stuck on the sliders then it can feel like a bad master cylinder, make sure they slide freely.
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Unread 12-04-2010, 06:22 PM   #12
EricsGreen98Tj
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take a piece or clear rubber tubing and a clear jar or cup. Put the tubing on the bleeder and stick the free end of tubing into the jar. Put about 2" of brake fluid in the jar and NEVER take the tube outta the jar!! When you bleed the brakes and open the bleeder the fluid outta the brake system will go into the jar allowin you to see if there are bubbles(air) in your lines. Try to use as small a piece of tubing as possible and try to fill the clear tubing with fluid b4 you hook it to the bleeder. bleed as Blaine said above and NEVER let the fluid in the MS run low during this process.

If you have milky looking fluid come outta your brake system then you have water in your brake system. Bleed this out till you get clean fluid.

You may have to bench bleed your MS since you let it run low to begin with...

HOPE YOU GET IT FIGURED OUT
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Unread 12-04-2010, 06:25 PM   #13
mrblaine
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Quote:
Originally Posted by EricsGreen98Tj View Post
take a piece or clear rubber tubing and a clear jar or cup. Put the tubing on the bleeder and stick the free end of tubing into the jar. Put about 2" of brake fluid in the jar and NEVER take the tube outta the jar!!
Why does that matter?
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Unread 12-04-2010, 10:52 PM   #14
EricsGreen98Tj
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Figured id put that out for all the air suckers out there....
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Unread 12-04-2010, 11:00 PM   #15
3vze28
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im just asking out of curiosity but what is wrong with his original bleeding technique? i only ask cause i used that technique a few weeks back and it worked out very well for me. the only thing i did different was i used 10 inches of clear tubing and a bottle with fluid in it and never let the tubing come out of the fluid. if this is the wrong way to do it i would like to teach myself the correct way, i just dont understand the pumping of the pedal with the bleeder open wouldnt it just go straight to the floor?

edit- i also went pass rear, driver rear, pass front, driver front, and never let my MC run out of fluid

edit again- the more i think about it the more i feel like this would have made the whole process go alot faster?
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