Bleeding brakes, air, air and more air

I've had my son do hundreds of pedal strokes, but the air keeps coming seemingly forever.

I can see no leaks.

I have a new brake mc, feed lines, one new caliper, two new bleed valves, and one new hose.

The braking system is really simple, so I fear that the only explanation is that the new mc somehow is pushing fresh air into the lines.

Sigh. I was hoping to do some driving soon.


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Brakes

Try putting grease around the bleed screw, or teflon tape

That is how it feels...

Since you replaced the MC all the lines have lots of air in them... the line you replaced(assume you mean the flex line and caliper if different then the new line) would be able to drain almost completely if both ends were open at the same time. Just keep reservoir as full as you can. Work one line at a time and make sure your son only pumps when the system has all bleed screws shut. Once it is pumped up have him hold the pedal to the floor as you crack the bleed screw while you hold your finger over the opening, you are making it act like a check valve when you do this. If you want to have him pump the pedal while you hold a finger over the opening you should feel lots of bubbles till it starts to run solid(you will feel it change) then have son hold pedal to floor and close screw, never taking finger off open screw. Keep close eye on reservoir so it can't suck air. Helps to have car on jack stands so you can work all four calipers one after the other. I had to go around the car twice but by the second round the system actually pumped up and my helper then did not pump until instructed. When you open the screw the pedal will fall to the floor and you need it to stay there until you shut the screw. You can wear rubber gloves and good idea to have goggles as it will spray with a little force when it is free of air. Good luck! Seems like it will never get right but this way has delivered for me every time!
Regards

Thanks, I'll try this.

But the volume of air that I have let out of the system so far, exceeds the total volume of the system by multiples. This puzzles me.




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It has been a while...

But I have been where you are! If the fluid drained from both supply lines while MC was out and you filled res with left side of car up you could have pumped the entire system from MC full of air just getting supply lines full, yes? Might want to set jack stands higher on right so the res is the highest point of system. If the supplies are plugged in with new seals and frimly and the hard brake lines are set and sealed you should not get any new air or if you do you would/should have fluid dripping on your feet as well. Forgot about the supply line detail. They make pump that attaches to the res with a tank and you just pump the whole system full but I am not certain the supply line seals would hold to pump fluid past seals in MC... A vacuum test kit can be used to "suck" the fluid through each line... I say "suck because the fluid is really pushed...ahh! Make sure cap remains off the entire time you are bleeding line. I do not know the entire system volume but my boneheaded understanding is this... lines (supply and hard, and calipers are a good bit of space) MC has two circuits (front and back) each pump moves a tiny bit of fluid out to four empty lines. If you were not blocking air from going back through screw air was just hanging in lines at highest point. How much air or pumping is not important how many times you fill res is and when you get things moving the level will go down! If it took the volume of the res to fill each line and you have not topped off four times then you would not even be close to having air out! This will be really fun after you get one line clear because the feedback on the pedal will encourage and the line that nearly free of air will grab a rotor! Once you get the hang of being the check valve you can pump each line quickly and this will be behind you. My dad is 85 and has no idea how to bleed hydraulic systems... he does lots of wrenching and until I surpassed his abilities he did all my work! Happy to still be here!!! Good luck hope this helps
Regards

Thanks again for the kind advice! I have flushed almost one liter of fluid through the system.

Rear right took forever, but finally came around. Rear left went smoothly. Front right never stopped pushing air, so I moved to front left. This one also seemed to be fine after a while. So I moved back to FR. And the air never stops coming.

I'll try again, and maybe move the car around a little to see if that helps.


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Was that the line you replaced?

That bleed after all that work is really tough! Unfortunately the air and fluid do not know how to behave in a queue so the air can be very stubborn. Sometimes I will have helper pump up hold then I crack screw and sort of sling shot the fluid out. Glad you made progress! Almost there!
Regards

I had the same problem... in the end I filled a bottle full of fluid, attached it with a hose to the nipple and squeezed - essentially forcing the fluid through the system backwards and letting it bubble up in the reservoir (make sure you don't overflow it). It seemed to be the only thing that finally worked

Nope. Something has to be totally wrong. Bled both rear and front left. Had reasonably hard pedal. Tried in vain to bleed front right. Now the MC is full of air again, and no pedal.

Something is wrong. How can the mc get full of air like this??? I have run a total of 1.5l of fluid through the system, and I'm back at square one.


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Arrrggghh!

So sorry to hear that! Do not know exactly where all you may have touched but guessing from the work you have done I would make certain you did not stress or crack one of the nipples to the MC. Been so long since I have done this job but if memory serves you have two supply lines, front and rear so if the supply to either is the culprit then the other is still OK... I would look at the front since it would not bleed on the one side. Being a bit hard to see up there you might try putting a little air in the res but that would make a mess if you do have a cracked supply. Never went so far back as to ask why you replaced the MC but if you did not replace the supply lines they may have been the problem all along. Hope not but if so, having a new MC is not such a bad thing. I recently replaced my entire fuel system including dropping the tank and cleaning it out only to find out my distributor was the problem... never give up! Good luck
Regards

Thanks

The old mc started squirting fluid on my feet, while the pedal started feeling dodgy. I replaced both supply lines, and the short hard lines at the pedal assembly. And the mc. Also one of the rear calipers due to a broken bleed nipple.

I would expect to get an honest leak if something had cracked...

Both fronts have the same supply, but the problem seems isolated to FL.

My only idea at the moment is to try to push fluid in through the nipple on the caliper and see what happens. Just for debugging purposes I guess.


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It's possible that it's an internally faulty master cylinder (either faulty from new, or damaged with all the excessive manual bleeding - it happened to me years ago).

For the sake of your sanity, replace the master again. At least this time, there will be some fluid in the lines, so bleeding should be quicker.

I have found that slow, gentle strokes without pushing the pedal to the floor is the least likely to damage internal seals. You should be able to get a firm pedal within 45 mins. Having car on stands so you can keep going around all four corners is good.

Good luck. These things are sent to try us.

Regards,

Mickey

I'm starting to fear that the new MC is broken. Luckily I have the spares to rebuild it. But I loathe dealing with all the messy disassembly again.

Being tested I am


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I'll be damned! Whaddya know! I just came home after taking the x for a spin in a rare warm summer night Oh what fun it is to ride in a 85 horse open sleigh

I got brakes! Rodgher is the winner. What finally worked was forcing fluid the wrong way.

I mocked up a system using pieces from a vacuum kit, using pressurized air to push the fluid up. Front left got this treatment.

Finished it off by vacuum bleeding the other three.

The pedal is somewhat low, but no problem locking up the wheels. So I'm good for now.


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Fantastic!

Welcome to the right side of things! Best part about these cars is that as frustrating as they can be at times, the payoff exceeds the trouble every time. Glad you got it sorted out!
Regards