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Discussion Starter #1
So I'm trying to bleed my brakes after replacing my master cylinder. I got a 65 6 cylinder with four wheel drums. I've gone around the car 5 times trying to get the brakes bled. I'm doing it with my wife doing the press, open, close, release method and got out all the big bubbles I could see, still the pedal goes to the floor with minimal resistance. The last time I fashioned up a hose and bottle that could be held above the wheel cylinder and did the press and release and still not see anymore air being released. I know this is a very common problem with our cars but come on....

This is actually the second M/C I've tried. The first I could not get any resistance in the pedal and when observing the fluid in the M/C I could not see any fluid jetting from the ports at the problem. I assumed it was bad right out of the box. The current M/C does show fluid movement when pressing the pedal but never gets to a hard pedal.

It's a dual bowl so at this point I would think I have at least one of the circuits would be bled out and I should have some pedal hardness. But the pedal still goes to the floor with minimal resistance..

Yes, both M/Cs were bench bled before installation and I have been very careful about watching the fluid in the M/C to prevent drawing it all out. I am so frustrated with this. I also just completed a suspension refresh with the Arning drop and I so want to get behind the wheel a drive this thing. Could this master be bad?

Gregg
 

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Couldn't care less about the bench bleeding. Doesn't do a thing for you actually.
There's a few different techniques to bleed them. You've been using the most common technique.
You may want to pump it up a few strokes and then open the bleeder. That's another version.
There's also a staccato version that helps dislodge bubbles. I had to use that technique a few years
back on a rear bleed. Took me about 3/4 hour to do that 5 minute job..... and I've done PLENTY over
the last 30 years. Pissed me off actually as I had to put the wife on the bleeder fittings to get the pumping
done.

It is possible to have more than one master (in a row) come up bad, right outta the box. Ask me how
I know. Depends upon where they're coming from and what lot it is if they're coming from the same source.

You might want to try some Russell Speed Bleeders at the corners. Just a suggestion. (I don't care
for the Earl's Solo-Bleeds though.... not the same quality)

ex-Global West GM
1991-1995
 

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One of my friends is having the same issue today and it appears there is a problem with the rear flex line at the axle.
To be continued...
 

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Discussion Starter #5
Tomorrow morning I'm going to get up early, warm it up then drive it slowly around the neighborhood. Maybe the vibration will help move the bubbles along.
 

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Harbor freight has a good system for 35 bucks. It does work with one person and a compressor.
 
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I use a Motive Pressure Bleeder, buy the adapter that fits your master cylinder and it's a one man operation. No more pumping the brake pedal, just pump up the reservoir and start with the right side rear

 
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I've been having the same problem, through several master cylinders, and have tried just about all the bleeding methods and tools. These include the Motive pressure bleeder (my favorite), traditional pumping the pedal, and vacuum bleeders, both the hand pump models and those that work with an air compressor. Learned really quickly to turn the air pressure really low on the latter; drained the m/c in a heartbeat.

I've also not had good luck with vacuum methods on my Wilwood brakes. I've not been able to get a good seal on their tiny bleeders, even with 1/8" tubing that is really difficult to get on the bleeders. Seeing air bubbles when pumping with the bleeder closed isn't a good sign.

I just installed some of the Russell bleeders, but maybe I should note that vacuum bleeders won't work with them.

The note about the rear end flex connection did start me thinking. It is the highest point in the lines other than the m/c.

But not sure what the "staccato" method is.
 

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So I'm trying to bleed my brakes after replacing my master cylinder. I got a 65 6 cylinder with four wheel drums. I've gone around the car 5 times trying to get the brakes bled. I'm doing it with my wife doing the press, open, close, release method and got out all the big bubbles I could see, still the pedal goes to the floor with minimal resistance. The last time I fashioned up a hose and bottle that could be held above the wheel cylinder and did the press and release and still not see anymore air being released. I know this is a very common problem with our cars but come on....

This is actually the second M/C I've tried. The first I could not get any resistance in the pedal and when observing the fluid in the M/C I could not see any fluid jetting from the ports at the problem. I assumed it was bad right out of the box. The current M/C does show fluid movement when pressing the pedal but never gets to a hard pedal.

It's a dual bowl so at this point I would think I have at least one of the circuits would be bled out and I should have some pedal hardness. But the pedal still goes to the floor with minimal resistance..

Yes, both M/Cs were bench bled before installation and I have been very careful about watching the fluid in the M/C to prevent drawing it all out. I am so frustrated with this. I also just completed a suspension refresh with the Arning drop and I so want to get behind the wheel a drive this thing. Could this master be bad?

Gregg
Feeling your pain. I’ve been fussing with poor pedal feel for months now. AT LEAST 1 1/2 gallons of fluid and I still can’t get it right. I try something and go through the entire bleed process and find no improvement It is frustrating but lucky for me I can just walk away from it for a few days at a time. At my age with poor close up vision and hands that hurt all the time just adds to it. My latest thought is that the car needs to sit more level. I’ve had it on jack stands so that I can easily get u see it, maybe being level will let some trapped air out.
Like I said feeling your pain. Drive on!
 

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Sometimes if a master isn't bench bled correctly it can hold air and seem like it will never develop a decent pedal. Sometimes. I have personally seen a guy just bolt on a replacement master straight out of the box, bleed at the wheels, and it worked just fine. My luck isn't that good.

Anyway, if you have doubts about there being air in the master cylinder, you can "com port" it. Inside it is a "compensator port". It allows a tiny bit of fluid to bypass internally momentarily. Skip the hows and whys. When you barely depress the pedal this port allows a tiny bubble of air to escape from being trapped in the valve. So if you "pat" the pedal like a hundred times all those tiny bubbles add up. And if your issue is having air in there, it's fixed. The technique also helps on hydraulic clutches and difficult motorcycle brakes.

Last I did this was on my '67. No idea why my super-experienced know-it-all master cylinder brake bleeding technique flunked, but it did. All I knew for sure at first was after bleeding I still had a very soft pedal. I hooked up my $12 USB camera to my phone and suspended it over the open master cylinder. Then I sat in the car and tapped the brake pedal. Sure enough, tiny bubbles. I patted until they finally stopped, about 10 minutes or so, and then the job was finally done.

Seems like we just went through all this with Kelly_H a couple of months ago. Did we?
 
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Discussion Starter #11
Yeah, I did a search on this issue and know that this is a very common problem. Two things I haven't seen mentioned before is the high point above the rear axle and your "com port" suggestion, so they are my goals for today. I guess I just have to be patient and outlast them.

Gregg
 

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Did you modify your brake lines? I mention it because on my previous mustang I bent some new lines, but for whatever reason I thought it would be a good idea to run one of the lines above the level of the MC....that was a huge mistake and the system was impossible to bleed until I re-routed that line and kept it under that level....any high point in the system is likely to have similar issues.
 

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But not sure what the "staccato" method is.
See post #10 below....

Anyway, if you have doubts about there being air in the master cylinder, you can "com port" it. Inside it is a "compensator port". It allows a tiny bit of fluid to bypass internally momentarily. Skip the hows and whys. When you barely depress the pedal this port allows a tiny bubble of air to escape from being trapped in the valve. So if you "pat" the pedal like a hundred times all those tiny bubbles add up. And if your issue is having air in there, it's fixed. The technique also helps on hydraulic clutches and difficult motorcycle brakes.

Last I did this was on my '67. No idea why my super-experienced know-it-all master cylinder brake bleeding technique flunked, but it did. All I knew for sure at first was after bleeding I still had a very soft pedal. I hooked up my $12 USB camera to my phone and suspended it over the open master cylinder. Then I sat in the car and tapped the brake pedal. Sure enough, tiny bubbles. I patted until they finally stopped, about 10 minutes or so, and then the job was finally done.
 

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As an option you could gravity bleed. I did my 70 this way, did the regular pump and bleed then I opened one bleed at a time for several hours with a full reservoir and let fluid drip out c/w trapped air. Seem to work and cant hurt anything.
 

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You say that you only replaced the MC - but I'm assuming that you replaced it because you thought it was bad, because you had bad pedal quality or something? You don't really say why you changed it out. That could be a key part of the problem. What were your symptoms before deciding to mess with this? It's possible that the MC isn't the culprit at all.

I just went through this as well - for years I have had issues with my braking system and my pedal not feeling nearly as hard as it should. Just always kind of squishy brakes, and I could NEVER get the rears to bleed correctly as they would always have a couple bubbles coming out. At the time it kind of seemed that it might be the bleeder screws not sealing right.

I recently completely solved by problem by overhauling the system. I installed stainless steel braided lines in place of all of my flex hoses, which were 10 years old anyways - because people say that they swell and balloon (giving you bad pedal feel) or can even swell shut (giving you no brakes). The SS braided lines are PTFE so they will never go bad unless I crush them somehow. Seemed like a good investment to me.

I also swapped out my master cylinder for a Raybestos unit, because I know them to make quality parts. No idea what brand was on there before but the top seal always leaked anyways and a new MC costs like 18 dollars so whatever. I spent FOREVER bench bleeding this sucker because I continually got tiny bubbles of air coming out of the rear port, no matter what I did. Someone said that maybe I was over-bleeding it and over-extending the piston, causing a bit of air to get sucked in and later expelled, who knows. I just bled that sucker until it quit spitting out anything but the tiniest bubble. It took me a good 45 minutes but I was not about to let it go.

The final thing that I did was put on rear discs. I did not like my rear drums for a number of reasons, but the parts quality available for them (I have a rare 11x2 size) was really terrible and I was continually going through wheel cylinders. I also encountered a number of incorrectly machined bleeder screws that would never seal right - although I later realized that it was likely the wheel cylinder that was incorrectly machined, because aftermarket speed bleeders wept fluid as well. When I did succeed in getting most of the air out of the system with a pair of good wheel cylinders with good bleeders, the pedal was still kind of questionable.

Now I don't know if maybe the flex line was the culprit here or if it really was the drums or what. All I know is that with some combination of those parts (new MC bled within an inch of its life, SS braided flex lines, new better quality rear brakes) the problem was solved and my pedal is now awesome.
 

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Discussion Starter #17
Well I was out there again today and I am still frustrated. I tried the staccato "com port" method and it seemed to have a slight positive effect but I did several hundred short strokes - about 2 inches - and not tiny taps so I guess this may still be a viable solution.

Kelly, I replaced the entire brake system about 7 years ago and at that time I converted to a dual bowl mc. The pedal always felt a little spongy but it would stop the car and not go to the floor if I stomped on it. This Spring as I was test driving some new upgrades the brake pedal went to the floor with no resistance and no amount of pumping would get it back. I got a replacement but couldn't get any pedal with it and I could not see any fluid squirting from the ports at the bottom when observing the the mc bowls so I gave up on it. Maybe I gave up too soon but I still have it so it could go back in. The current mc is made by Centrex.

When I refurbished the brakes years ago I got new SS lines, wheel cylinders, mc, hoses and the rest. Everything was purchased out of catalog chosen for price, fit and expediency. The suggestion that my hoses may be the problem resonates for me as I'm sure they are a cheap quality. I just did a little search for braided SS hoses and see bewildering amount of choices, can anyone point me towards something that would work for my original configured system.

Thanks everyone who has taken time to offer help and suggestions.

Gregg
 

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I've had similar bleeding problems lately and I think I figured out why. The last few brand name replacement master cylinders I've bought have been completely lacking residual pressure valves. These are the valves that sit behind the tube seat inserts in the ports. I guess parts suppliers figured out they can save a cent per unit by leaving them out, and difficult bleeding and poor pedal feel isn't their problem. Plus then they get to sell the same part for disk and drum applications. Welcome to the future.
 

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Verify that your shoes are adjusted correctly.
 

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Are you doing this by yourself? My way of doing it like others is to start in the rear passenger and get it bled the best I can. Then I call upon my assistant, wife, to put pressure on the pedal and open the bleeders till the pedal starts to go down. Repeat this three or four times for each wheel.
 
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