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Old 05-20-2009, 12:04 PM
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Lost pedal pressure

When I quit bleeding the brakes some time ago I had good pedal pressure. Now I have none. I started the bleeding process over again. I borrowed a small hand held bleeder pump and put the hose on the bleeder screw. I get streams of bubbles like blowing through a straw but it draws fluid. Is the pump drawing air around the bleeder? I get the same result at every wheel so I can't think there is that big of a leak anywhere. Front and back are different systems. No puddles under the hot rod, no sign of dripping at joints...no pedal pressure. I can't seem to get this bled. I'm going nuts.
I should add this is a corvette style MC, manual 4 wheel discs with a proportioning valve.
So what do I do????

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Old 05-20-2009, 12:24 PM
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Hi try clicking on the link here its an article i contributed , it may help .http://www.crankshaftcoalition.com/w...ome_basic_tips
I hope it appears ok if not why not do a search . best of luck .
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Old 05-20-2009, 05:28 PM
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Try a gravity bleed on the beast, as long as the MC is higher then the wheel cylinders it will work, I got the bubble thing once when I tried the new and improved way, if I can not gravity bleed I use the old reliable wife's foot and leg motion...
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Old 05-20-2009, 06:27 PM
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Quote:
Originally Posted by 46highboypu
When I quit bleeding the brakes some time ago I had good pedal pressure. Now I have none. I started the bleeding process over again. I borrowed a small hand held bleeder pump and put the hose on the bleeder screw. I get streams of bubbles like blowing through a straw but it draws fluid. Is the pump drawing air around the bleeder?
Yes. I wrap a couple of wraps of teflon tape around the bleeder if I'm vacuum bleeding to get rid of the air bubbles.
Be aware that sometimes vacuum bleeding can draw air past the cup seals in the master cylinder or a wheel cylinder. Disc brakes are no problem with a vacuum bleeder, the seals are 2 way seals.



Quote:
I get the same result at every wheel so I can't think there is that big of a leak anywhere. Front and back are different systems. No puddles under the hot rod, no sign of dripping at joints...no pedal pressure. I can't seem to get this bled. I'm going nuts.
I should add this is a corvette style MC, manual 4 wheel discs with a proportioning valve.
So what do I do????
My suggestion is to re-bench bleed the master cylinder, as you will not get all the air out by vacuum bleeding a wet system, then either gravity bleed the system, pressure bleed it or do the pump /hold/bleed method.

When you bleed the master, make sure you restrict the ends of the tubes that go from the ports into the reservoirs, the pressure helps the cup seals work as they should. The bench bleeding kit you got has a plastic clamp that is supposed to pinch the hose... Also let the piston retract s l o w l y...if you let the piston out too fast, it will draw air past the cup seals. I turn the master so the end is uphill a little when bench bleeding. This helps all the air go towards the port end. Make sure there is no air coming up through the supply port in the reservoir, (the big hole), it can take a while to get every air bubble out. Then leave the bleeder hoses connected while you install the master, only disconnect them just before you hook up the lines.

Which rear brake calipers do you have? The GM calipers with e brake suck to adjust to get a pedal. Also, if you got a set of GM metric calipers for the front that are the low drag type, those can suck up a bunch of pedal travel...

later, mikey
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Old 05-21-2009, 08:14 AM
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Thanks Guys,
Yesterday, while I had the rod up on jack stands to do the rear calipers I rolled the wheel as I pushed the brake (it's a short wheelbase) and the brakes would stop the wheel. I have been working on this project forever it seems and the rotors are rusty so I can see where the pads have cleaned them off. The brakes are working a little. The fronts haven't cleaned. I let it down and tried again to back up, the brakes held at idle, stopped after a foot or so of roll but would not hold on the down incline against the engine pull.

I was advised to put plugs in the outlets on the MC to test the pedal/MC and it was hard, stopped dead after only an inch of travel. The first time I bled the system I used the gravity way so I may try that again. I still don't understand why the loss. It had sat for several weeks while other stuff was done and of course the brakes were not used, shouldn't it have held?
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Old 05-21-2009, 08:45 AM
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Hi . im just wondering if you have tried what i suggested that is carefully clamping all the flexible brake hoses and then releasing one at a time that way you will identify where the problem is .Its worked for me this past 30 + years . tom.
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Old 05-21-2009, 12:20 PM
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Tom,
I don't have any "soft" lines, they are all braid covered. Thank tho. Just talked to friend and he has volunteered to stop by and look the situation over and help bleed it if we can. I'l let you know how we do. Thanks all again!
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Old 05-22-2009, 07:02 AM
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Latest update...
My friend came by and we bled the brakes again, checked everything over and bled them again. Still not much pedal. We looked into adjustment on the pedal travel and discovered that the push rod probably is not long enough. As all the parts on my rod are new or not stock I had no push rod for the MC purchased from the parts store and a guy I know modified one of his spares. This is par for my project that I get or make stuff for it and then don't get to actually use for a long time. He was guessing the length based on my discrition of the pedal bracket. Anyway, now it's time to make a new one. I'll let you know how it works.
Thanks again for all the helpful ideas!!
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Old 05-25-2009, 01:58 PM
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Last update... I think the longer push rod is going to do the job. It rained out my farm flunky job today so I could put it all back together again. Lots of pedal now, may have to adjust for shorter (?!?). I would back out and try the system but it's still raining. I sure this is going to work, I may be able to make GoodGuys Indy yet.
Thanks again to everyone who offered help!
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