Constant air when bleeding

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Red_Duster

Red_Duster

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Ok, no matter how many times I bleed the brakes I am getting air in all 4 corners. Car is a 1968 Dart, factory KH disk car. I did the 8.8 swap for rear disks and 73+ swap for BBP. All new soft lines and calipers on all 4 corners. New 15/16ths master that was bench bled. No visible leaks, no matter how much pressure I put on them. I DO HAVE pedal, but have gone through several quarts of disk brake fluid, and no matter how many times I bleed them (with the buddy) system, I’m still getting significant bubbles on the first two holds. Ideas?
 
Red_Duster said:
Ok, no matter how many times I bleed the brakes I am getting air in all 4 corners. Car is a 1968 Dart, factory KH disk car. I did the 8.8 swap for rear disks and 73+ swap for BBP. All new soft lines and calipers on all 4 corners. New 15/16ths master that was bench bled. No visible leaks, no matter how much pressure I put on them. I DO HAVE pedal, but have gone through several quarts of disk brake fluid, and no matter how many times I bleed them (with the buddy) system, I’m still getting significant bubbles on the first two holds. Ideas?
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Try shorter pedal strokes and slower pedal returns.
Heck, even try gravity bleeding.
 
Bleeders at the top ?
All Pads in solid contact with rotors ?
Very unusual.
Are you closing the bleeder before the pedal is released ?
 
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Master cylinder, not properly bench bled would be my guess.
 
Check all your new brake line conditions for a leak, could be pulling air in at a few places
 
Lift the *** end of the car so that the master is nose down... so any trapped air can get out into reservoir.
 
dadsbee said:
Lift the *** end of the car so that the master is nose down... so any trapped air can get out into reservoir.
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I’ll give this a try, and the shorter pedal strokes. Bled plenty of cars without any issues. Normally I hate changing more than 1 thing at once and this is exactly why!

Just a got it back from paint/body and threw a ton of parts at it.

Assuming I didn’t get a good bleed on the master (anything is possible) wouldn’t that just give a mush pedal and not continuously introduce air i can push out the bleeders? And a failed master introduce air without actually leaking fluid?

It’s just bizarre that I’m losing pedal and getting bubbles it on all 4 corners after sitting approx 30 min.
 
dadsbee said:
What, or who's, new master?
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No name generic 15/16s chrome unit. Maybe it’s time to pull the trigger on a Dr. Diff unit and see if it’s the master. Hate to just throw money at the problem but I’ve been trying to bleed it for a few days now and nothing is working. Lines and flares are all good. No leaks. Bleeders are all up. Grrrr!
 
As memike said. A badly flared line or loose line will suck in air yet not leak fluid.

At this point I'd check every fitting. If they seem good then I'd take the lines off the master and plug the ports. Find a firm pedal then you know it's good. Then work your way through each line and fitting. Could also be a bad distribution or proportioning valve sucking in air.
 
Master can also suck in air at the shaft seal. Slowly cycle the pedal and have someone watch for rising air bubbles into the reservoir.
 
Did you bench bleed the master cylinder?
 
dadsbee said:
As memike said. A badly flared line or loose line will suck in air yet not leak fluid.

At this point I'd check every fitting. If they seem good then I'd take the lines off the master and plug the ports. Find a firm pedal then you know it's good. Then work your way through each line and fitting. Could also be a bad distribution or proportioning valve sucking in air.
Click to expand...

RustyRatRod said:
Did you bench bleed the master cylinder?
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I bench bled it in the vice, no issues getting it bubble free. After research on here, I also cracked the lines on the master with pops holding one pump to see if I got anything at the master. The car HAS been sitting for a little over a year, other than in and out of a paint booth, but I wouldn’t think a seal would fail that fast?

I’m not a brake expert, but I’m sure someone can educate me: are the front and rear circuits seperate lines to the block and then to the front/rear? To get bubbles on all 4 corners wouldn’t it need to be the block or upstream from there? I could understand an issue at the the rear since I bent and flared all those myself-but they’ve all been replaced this week by my pops, who is much better than me. Front were just hoses- the existing lines never had an issue with the KH brakes. Would an issue in the rear put bubbles at both front calipers? Sorry if that’s an ignorant question.
 
There are no ignorant questions. What is your bleeding procedure? Should be RR, LR, RF, LF. I use a glass jar with a piece of vacuum hose stuck on the bleeder valve. I put about 1/4 of a jar of brake fluid in the bottom. Put the end of the hose in the jar and make sure it's submerged in brake fluid. Get your helper to pump the pedal until you have no bubbles. Close the valve and proceed to the next.
 
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