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I give up...brakes go to the floor !!!

Mike Miller

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I have a 74 charger and just replaced all of the wheel cylinders, calipers ,and master cylinder.. the old system was contaminated after years of sitting unused. Having done this many times back in the 70s and 80s this is not my first. Bench bled the master, had to make a new feed line for the front going into the proportioning valve. Bled system over and over ..pedal went to the floor. Thinking new m/c was faulty i pulled it and replaced yet again with a new one.. same results. No air coming from all 4 bleeders, used vacuum pump, old school 2 person method.. same thing. Short fast pumps will build pressure, than right to floor again. No fluid leaking anywhere.. cant build pressure to bleed correctly.. bled fronts at hose connections, no air.. any suggestions ?? Thanks..
Mike
 
wow thats weird...did you replace the outboard rubber lines too?
do you have a booster?..i would assume you do on a 74?
and is it holding pressure?
 
Hmmm, have you tried to bleed the proportioning valve, distribution valve, etc. to ensure that there is fluid going there? I have had this happen a time or two and it always came down to a significant amount of air in the system someplace. The last one I did i bench bled the MC, then each valve below that, I think I used a vacuum pump to draw fluid back to the rear brakes.

Since then I have invested in a wide variety of bleeding devices to include a Motive brake pressurization tank which works pretty well as it forces fluid through the system. Last summer I got a Phoenix "pusher" system which does work in most situations.
 
Check all the rubber lines for ballooning while someone
pumps the Master = they are often a problem when car sits
awhile!
 
One thing to be aware of is that the P valve has a sliding valve inside it under the brake light switch which if it is stuck to one side will not allow bleeding on that side or at least make it very difficult
 
70chall440 & GTX John both have very good ideas. I'm going with TWO bad master cylinders as my odds-on favorite....but I REALLY like 70chall440's idea of just start burping air out of each connection, maybe 1 brake at a time and try to burp out air. I mean, if it's all new then nothing should be rusted stuck...not a bad thing to try if you've tried everything else. MUST be air or bad master cylinder (as you already know)
 
Just had basically the same thing, fixed on the first new master cylinder. The original master cylinder would bench bleed great.
 
You do have the calipers on the correct side? The bleeder needs to be the highest point.
 
Had that on the Bird after having the front lines apart. Crank the rear shoes tight to the drum and try pedal pump bleeding again. You need the pressure on the rears to pop the front proportioning valve open before they'll bleed correctly.
 
Had that on the Bird after having the front lines apart. Crank the rear shoes tight to the drum and try pedal pump bleeding again. You need the pressure on the rears to pop the front proportioning valve open before they'll bleed correctly.
70 service manual says gravity bleed the front disc brakes, so as not to damage the proportioning valve. Ask me how I know.
 
old school 2 person method.. same thing. Short fast pumps will build pressure, than right to floor again.
Mike

So when your able to pump up the pedal, and keep it under pressure while the second person opens the bleeder you get no air, just solid stream of fluid?? starting at passenger rear, moving to drivers rear then to passenger front then lastly driver front. I would perform this 4-6 times on each cylinder. it may take three shots on each line before you see the trapped air shoot out . don't run MC dry or you gotta start over. Always has worked for me.
 
Just for safety sake if the car has sat for "years" I would replace All lines both flexible and rigids. They corrode from the inside out. You can't see inside a blocked line. Only external hernias'. Are you using "new" master cylinders or "rebuilt?" Avoid rebuilt's at all costs.
At this point all new lines would only be a couple hundred dollars. Also avoid s/s solid lines. Very hard to get the fittings to seal.
The bleeding procedure is pretty basic and sounds like you are doing it.
Always go back to the beginning when you are stumped on something and recheck everything. It also doesn't hurt to have another set of eyes helping you.
If you set the parking brake when you bleed the fronts, the rear shoes will be locked to the drums so there will be no free play.
 
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Had that on the Bird after having the front lines apart. Crank the rear shoes tight to the drum and try pedal pump bleeding again. You need the pressure on the rears to pop the front proportioning valve open before they'll bleed correctly.
Agreed. :thumbsup:

You must start with the basics;
Adjust the rear shoes until they are touching the drums, otherwise you are expending all that pedal travel on moving the shoes without creating any pressure in the hydraulic system.

Yes, also follow the advice above for the proportioning valve.

And it also helps that the drums are skimmed flat, and front calipers have shoes in great condition.

The less the mechanical travel when bleeding, the better and faster the results.
 
You didn't swap calipers from side to side by accident? If not, clamp all 3 rubber lines with Vice grips. I know I'll take heat for this but I've done it many times with no failures. What does the pedal feel like now? If its good, remove one clamp at a time until the pedal sinks. Then chase that circuit.
Doug
 
Cheap Oil can from HF. Bought one a big one and some flex line that fit the bleeder on the wheel cylinder. Pump from the longest line in the back. Keep checking you brake hopper for air and keep it about half full. Some times better to have a second set of eyes on the master cylinder reservoir. This seems to work well for me.
 
Just curious but did you confirm that the bore is the correct diameter?
 
Wow!! Thanks all for the input.. the rubber lines are also new.. and i flushed where they meet at the rubber hose to be sure prop valve was open..no problem with flow. i always start with r/r wheel amd move to next longest lines when bleeding. .the idea of the drums being tight to the shoes is one i will try next.. the m/c and wheel cylinders are new, the calipers are rebuilds.. front brakes are snug against rotors as they should be, the rears bleed with very little pressure so i am going to look there next.. thanks all for your replies, will post again when i find the problem.. and i have no power brakes.. no booster.
 
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