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Can't get air out of brake lines after hours of bleeding...

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Old 03-09-2012, 11:34 AM   #1
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Can't get air out of brake lines after hours of bleeding...

Let's start from the beginning, hopefully someone here can help...

(This is on an '03 s10 crew cab zr5)

Brakes needed changed about 2 months ago, but being completely broke until taxes, I used the truck only to/from work hoping I could last until my return... return came this week, I was going to do it this weekend when yesterday morning my brakes went completely out...

Replaced both front rotors and rear pads. Front Passenger caliper ceased so i replaced it as well. I bled the brakes (in order, pass rear, drive rear, pass front (which was replaced) and the drive front). Rears were fine, but I got alot of air out of both front brakes, bled them for about 2 or more hours. Once we were confident that we were not getting any more air out of them we tried to get pressure in the pedal to no avail.

First thought was the master cylinder, but we bled it as well and it was pumping brake fluid out... now I'm at a loss for how to find or get out the air that's in the line...



Any ideas? I'm at a loss here... and my pride is the only thing stopping me from dropping more money on a mechanical, haha...
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Old 03-09-2012, 11:57 AM   #2
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Re: Can't get air out of brake lines after hours of bleeding...

I swallowed my pride years ago when it comes to air in brakes lol. A few issues/questions: What is your bleeding method? Did you bleed the MC first and did you "bench" bleed it, ie removed from vehicle? If the new front caliper is a rebuild, it might be defective - I've had that happen. Are you sure there is not air in the ABS controller? I assume the MC reservoir is not running empty in the bleeding process, that will obviously draw air in.

I try to avoid bleeding myself and pay the $100 or so to have a pro do it. It is just a messy bitchy job to DIY in my opinion.
Old 03-09-2012, 12:09 PM   #3
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Re: Can't get air out of brake lines after hours of bleeding...

Bleeding method - 2 person, pumping/bleeding screws, and yes, we bled the MC first, didn't take it out at all so we didn't bench bleed it- but it was pumping brake fluid out. The caliper was new, so it should be fine. No the reservoir is not running empty, I'm not sure if air went in that way when my caliper ceased because I lost alot of brake fluid when that happened, and buddy that was helping filled it before I looked at it...

I never considered air in the ABS controller... I've never dealt with that before... I'm going to look into that now...
Old 03-09-2012, 01:16 PM   #4
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Re: Can't get air out of brake lines after hours of bleeding...

Yeah check out the ABS controller, very possible that is where the last of the air is and let us know how it turns out. If it is not the ABS, just to verify that on the bleed method, I have found this to work best: Open bleeder screw first, depress pedal, then close bleeder, allow pedal to return. The depress pedal/open bleeder then close bleeder then allow pedal to return method seems to just move air around inside the system.
Old 03-09-2012, 02:31 PM   #5
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Re: Can't get air out of brake lines after hours of bleeding...

until my help arrives i'm trying some one man avenues... got a tip to jack front end up rather high and let sit for about an hour, this should dislodge any bubbles caught in the booster/master, also can dislodge bubbles in the calipers...
Old 03-09-2012, 02:34 PM   #6
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Re: Can't get air out of brake lines after hours of bleeding...

Bleeder screws are at the top of the caliper, right?
Old 03-09-2012, 02:48 PM   #7
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Re: Can't get air out of brake lines after hours of bleeding...

Just to eliminate one possibility, you do have the correct caliper for that side, the bleeder is at the top? Don't laugh, I've seen that before and you will never get the air out.

4 basic methods of bleeding.

Gravity
If all you opened was the hose connection to the caliper just leave the bleeder open and let it run out until no more bubbles. You must make sure the reservoir does not run dry or you will draw air into the system. Getting air in the ABS module can be a b!tch the get out. This method works well if all you open is a connection to a wheel cylinder or caliper.
Works most of the time and is usually all that is needed for non-ABS brakes.

Pressure by pumping the pedal
This is as described above, pump the pedal and hold, open the bleeder while pressure is held and close when the pedal is down. This moves fluid through the system fast but is at risk for aerating the fluid if pumped too fast. It CAN draw in fluid as the pedal returns if the wheel cylinder or MC cups are old and hard or worn. Not the best for many late model ABS systems. This is best done after gravity bleeding.

Pressure by a tool of sorts
This is simple if you have the tools. Just fill the MC and attach the pressure bleeder and open the bleeders to bleed. Moves fluid well without aerating fluid.

Reverse bleeding.
This is pumping brake fluid in the system at the bleeder screws. This is a last resort but works well as air rises easier than it goes down, so pushing the fluid up into the MC will purge air better. Works well with most ABS systems.

In general I like to get most of the air out before I start the "real" bleeding. That means that if I replaced one caliper, I will gravity bleed that wheel first to get most of the air out. If all I want is a good pedal and not concerned with flushing I call it good at that point. This will almost always do it.

I avoid pumping the brake pedal if at all possible. Years of use will wear the first part of the bore and pressing the pedal pass 1/2 way is inviting a MC failure. The old MC cups are hard but have expanded to accommodate the wear. Pushing the MC piston into the unworn part of the bore compresses the old hard MC cups and they often do not return to their previous state and will now bypass fluid resulting in a low pedal.
Old 03-09-2012, 03:02 PM   #8
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Re: Can't get air out of brake lines after hours of bleeding...

Yes, the caliper is the right one for the side... and not laughing, as much research as i've been doing that seems to be a big cause of these problems...

my issue now is figuring out how to bleed to the ABS system, i can't find any information on what system my truck has and the methods to bleed said system... all i've found so far is that i need some sort of special tool for bleeding an abs system... i'm hoping that when my helper arrives that one more thorough bleed of the system will do the trick
Old 08-11-2013, 12:43 PM   #9
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Re: Can't get air out of brake lines after hours of bleeding...

Thanks for posting this info AWD.
My 88 s 15 has been giving me grief with a brake problem that has me kinda puzzled.
I have been using the "pump 3 times and hold with someone opens and closes the bleeder" method for years with success but maybe it is time to change my ways. A while back, a line broke so of course the MS went to the floor. the brakes never seemed great after fixing the broken line so I suspected the MS was pooched. I replaced it but I still have same problem which is brake seems hard not running but travels almost to the floor when running and poor brakes. No stopping on a dime for sure. Also replaced other worn parts like shoes and pads, inspected for leaks, seized components ,etc.
I noticed that when I put on the brakes, it revs higher for a second then goes back to normal but I don`t recal it doing this before so I am thinging booster now. Couldn`t find any leaks in lines and booster seems to hold a vacuum so I am just guessing without understanding the problem .
I have been doing the body over for awhile and now that it is done, I am back to this problem. While it was sitting for a long time in one spot,(with the nose up high so the MS was level) I did try a gravity bleed and didn`t notice any leaks.
Two questions: If the MS has a cup stuck, etc,how will you be able to tell? I am guessing when you bench bleed it , you will only get fluid out of one port.
The other is any suggestions for my sitiuation. BTW, I initially vac bled my system as I didn`t have an assitant, but I did the 3 pump thing later when I wasn`t having any luck.
Old 08-11-2013, 02:31 PM   #10
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Re: Can't get air out of brake lines after hours of bleeding...

Couple of tricks I have. I work at a shop so its easy for me since I have multiple tools to push it out. Doesnt help at home. I have 2 tricks that will most likely apply to you. One costs money.

1st trick, you might have air in the ABS line. Since you have no scanner to command the pump to run, you need to do it manually. If the truck can drive without crashing into something, find some gravel. You need to make the ABS come on by slamming on the brakes and allowing the system to pump and purge. This will move more fluid out into the lines and hopefully air is in there somewhere.

2nd, Harbor frieght vacuum pump. Usually on sale for 15-20$ and they can be a life saver. I have used both just the regular pump, and the one that might be more expensive, but its for specifically bleeding brakes. Both do about the same but the regular pump can be a slight hassle to put a few lines together to go small enough to clamp onto the bleeder screw.
Usually the pump method requires 2 people. You can have one person holding the brake pedal down (usually not enough power for it to be up) and one will pump for a few seconds doing the same rotation sequence. Just make sure you check your fluid every time yyou switch tires.

You can pump as much fluid out as you would like which I usually pump out alot. This is basically doing a brake fluid flush as well so you wont have to worry about it later. Once you see cleaner fluid you should be good to go. If you still have a problem, its your master.

I have seen masters go out multiple times just randomly doing a quick and easy pad slap. You can mess up some worn seals by pushing the piston back into the caliper.

With this information, you should be able to get it. Its going to require some work, but this should eliminate any air in the system, or any other problems the trucks braking system has.

-Mark
Old 08-11-2013, 07:53 PM   #11
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Re: Can't get air out of brake lines after hours of bleeding...

FWIW, I never push the old fluid back into the system. I just did the front pads last night, and I cracked the bleeder screw while I compressed the piston. I see no point in forcing that dirty fluid into the master cylinder, plus since it's been kept topped off it would overfill.
Old 07-25-2014, 04:06 AM   #12
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Re: Can't get air out of brake lines after hours of bleeding...

Hello
do you finf excatly what was wrong ?
frend in France have the same problèm and nobody find what it is
he change the MC, the rear caliper and after 2 weeks home and mecanic it is exactly same problem
now mecanic say it could be ABS ....
thanks if you have new idea
Old 07-25-2014, 05:51 AM   #13
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Re: Can't get air out of brake lines after hours of bleeding...

Tell him to bleed the master first, then re-attach the brake lines to the master and bleed at each wheel. this will work regardless of the ABS or no ABS.
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