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  #1  
Old 03-18-2002, 03:48 PM
arter's Avatar
arter arter is offline
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Location: audubon, nj
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Can't seem to get the brakes up. Have 79 axles with rotors/drums on new 86GW style master cylinder. New rotors, calipers, braided steel lines, hardline to rear brakes, and wheel cylinders. Bench bled new master, had hard pedal with the plugs in, before attaching brake lines. Been bleeding for almost a month now, get pedal with engine off, goes to floor with engine on and booster working. Since the 79 had the older style cast master cylinder could this be my problem? Runs good, just can't stop!
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Old 03-18-2002, 04:05 PM
jeepbob jeepbob is offline
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That should not be a problem as the parts on the axles should be the same. I suspect either air trapped in the M/C or proportioning valve. I do not know the procedure on bleeding the porp valve for the later rigs but on the 79 you had to push in the button on the valve.
BTW check to make sure that the rear shoes are adjusted up as this will also cause a low pedal, if you can pump them once or twice and the pedal gets hard then this would be your problem.
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Old 03-18-2002, 04:23 PM
O.P. O.P. is offline
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Another possible way to check where air is at is to clamp off the flexible hoses and see how that makes the pedal feel. Clamp off rear hose, if feel better then there's air in rear or rear are way out of adjustment. Clamp off fronts, if better then there's air trapped in calipers. If none of this makes it any different then the air is in system before it get to hoses. Namely Mstr cyl or proportioning valve. You said the pedal was good before attaching lines to mstr cyl so it's probably not there.

I've had no personal experience with the stainless braided brake lines, but it came up in a conversation with a friend who races and he told me that a system with the braided lines will have a more spongy pedal than with standard lines. Don't know for sure about this, there are bound to be others with more experience that can help in that area.

There's a tool that slips on the end of the proportioning valve that keeps it from tripping when you bleed the system. Your local parts store should have one of them and the brake hose clamps.

Hope this helps out.

O.P.
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Old 03-18-2002, 11:24 PM
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it's just my opinion but it sounds like you may have sucked air back into your master cylinder you may want to bench bleed it again and when you hook up the brake lines gravity bleed it for a while to move the air bubbles down the line far enough so when you pump your brake for the bleed off you don't suck air back into the master cylinder. i let mine go for about an hour or so till clear fluid was coming out had no probs. as far s useing the newer mastercylinder you should be ok i personaly choose an older model becauseit is cast and half the price of the alluminum model
and i am hopeing the cast model will last longer than the alluminum any way just my thoughts not yours Ryan
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Old 03-19-2002, 01:50 AM
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Guess I'll disconnect the lines, plug the m/c, and see what the pedal feels like. Any doubts, take off and bench bleed again (not level in wag). Put back in and gravity bleed. Question: since this system was practically dry before all this, what should I be doing with the proportioning valve? If I remember correctly, when I gravity bled before, the front brakes didn't bleed with the pin in. BTW - friend of a friend said that brake fluid is really whale oil, anyone else ever hear this?
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Old 03-19-2002, 04:36 AM
jeepbob jeepbob is offline
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It is actually Ethylene Glycol based, unless it is DOT 4 which is silicone based and not compatable with the Glycol based DOT 3.
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  #7  
Old 03-19-2002, 05:50 AM
J20fan J20fan is offline
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arter, I just went through this recently. I had replaced my brakes etc. and after checking all (except the master) was secure, started to bleed the brakes. Well the brake fluid was everywhere but in the master cylinder, there was only air in there now. So I disconnected the lines at the master and screwed in 2 pieces of brake line I cut off my parts rig and attached hose to them. I put the ends of the hose in the master cylinder each to its correct reservoir and had my friend work the pedal by hand slowly about a 1" stroke untill the cylinder was purged. I saved a bit of time and it worked well after I gravity bled the system.

[ March 19, 2002: Message edited by: J20fan ]</p>
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  #8  
Old 03-19-2002, 10:28 AM
rigger rigger is offline
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j20fan that is exactly how i bench bleed mine all the time right on the truck i have two plastic fittings and two clear plastic hoeses submerge them into there respective resiviours and presto pump the brakes slow hold for like a min at the botom of stroke repeet until no air in the clear lines.
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yaya looks nice,but does she GO!?<br /><br />1981 cherokee lerado 360/727/208/d44/amc20 Wt<br />posi fnt & bck<br />.030\" overbore <br />crank shaved .010\" and line bored<br />balanced blueprinted<br />crane cam ,lifters<br />edelbrock preformer intake<br />edelbrock 650cfm four barrel carb<br />Tfi upgrade<br />3\" dynomax ultra flo exaust<br />custom lift springs <br />31\" bfg at\'s<br />CBR929 firblade<br />68 roadrunner 383 12.2 1/4 mile<br />original #\'s car
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