Nissan Pickup Loosing Brake Pressure

1987 NISSAN HARDBODY
4 CYL • 2WD • MANUAL
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BLUECOPPER
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My 1987 pickup has made my mechanic more confused the a rubix cube. I went to do some servicing including adjusting the hand brake and to check and service the front brakes. A leak was noticed on the left caliper so a repair kit was purchased and that corrected. Now after bleeding the 4 lines we noticed that the brakes went straight to the floor. Pumped up the brakes and it builds up pressure and after resting for maybe 15 secs and depress the brake pedal it went straight to the floor.

The mechanic changed the brake cylinder and the same thing. After doing some checks he said that the left caliper was expelling air in the oil. So he block of the brake line to the left caliper at the brake cylinder and there was brake. He block off the same line where it joins with the brake hose and there was brake. After removing the block the brake pedal went straight to the floor. He then used a vice grip to clap the hose it self and when tested there was brake. He decided to put on a new brake hose but the problem persists. So right now every thing points to the caliper as being the fault but the odd thing is the caliper isn't leaking any oil since replacing the rubbers in it.

What do you guys think of this? This thing is driving me up the wall because i really want this fix soon.
Jan 30, 2011 at 2:25 AM
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WRENCHTECH
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Go out and look at the caliper and find out if the bleeder is above the input line or below it. and let me know.
Jan 30, 2011 at 2:53 AM
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BLUECOPPER
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Its slightly below
Jan 30, 2011 at 3:06 AM
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WRENCHTECH
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OK, problem solved. When he took the calipers off, he put them back on on the wrong side of the truck. The bleeder has to be at the highest point or it will trap air that you can never get out.
Jan 30, 2011 at 3:09 AM
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BLUECOPPER
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He only took off the caliper on the left side. Maybe i'm remembering the position of the bleeder wrong. Its not here but at the mechanic, but thats how i remember it.
Jan 30, 2011 at 3:12 AM
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WRENCHTECH
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Check it and find out. If the bleeder is not the highest point, you can never get it bled. It's a common mistake
Jan 30, 2011 at 3:14 AM
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BLUECOPPER
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will do...
Jan 30, 2011 at 4:14 AM
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BLUECOPPER
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The bleeder is actually higher. It appeared lower than it is due to the elevation of the front of the truck. Can the angle of elevation be a problem for bleeding?
Jan 30, 2011 at 3:11 PM
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WRENCHTECH
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It shouldn't be. If you can get a hard pedal by pinching off that hose, then the problem can only be in that caliper or the way the pads are installed. Take it apart and check it again.
Just double check that the hose isn't ruptured internally after the point where you were crimping it and stretching out under pressure.
Jan 30, 2011 at 3:18 PM
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BLUECOPPER
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I had bought a new hose thats why i said that everything now points to the caliper. The mechanic said he had tried again this morning and he got a little brake but doesnt know what else to do. I'm going there now so am gonna see if he will remove and reseat the brake pads and see if there is any difference.
Jan 30, 2011 at 7:55 PM
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Ok the mechanic said he pulled down both calipers and cleaned them out but this time he said he did not pump the brakes to bleed them. He poured in oil and cracked the bleeder and made it bleed on its own and when it stopped bubbling he tightened the bleeder and there was a little brake. So now i got a little brake but its very low... sigh
Jan 31, 2011 at 2:38 PM
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WRENCHTECH
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I can't understand why this guy can't see the problem if you have already isolated it to the caliper by pinching it off. I beginning to question the competence of this guy.
Jan 31, 2011 at 3:14 PM
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BLUECOPPER
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Well at this point i guess whats left to do is change the caliper it self.
Jan 31, 2011 at 3:20 PM
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WRENCHTECH
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No, you shouldn't have to. That pressure is being released somewhere and if the caliper is not leaking or binding and has no air in it, then there is nothing wrong with it. The problem should be obvious. The pad may be bent or not seating securely but that pressure is being released somewhere, assuming you have a solid pedal with the line pinched off.
Jan 31, 2011 at 3:31 PM
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Ok just an update... the pickup was brought to another mechanic and the situation explained and what was already done. After there own testing the booster was found to be the problem and has been changed.
Feb 5, 2011 at 1:38 PM
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WRENCHTECH
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That would mean that your test result of everything being OK when the line was pinched off was incorrect.
Our conclusions are only good when the symptoms given are accurate.
Feb 5, 2011 at 1:43 PM
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BLUECOPPER
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Well the symptoms i explained was what happened not sure why but thats how it was. When the line to the left wheel was blocked off the pressure build up would not fall. Sounds so strange.
Feb 5, 2011 at 2:19 PM