air in brake system

[rm6p]

I cannot bleed the air out of the brake system after a caliper change. 1970 Roadrunner with power disc/drum brakes. The car was originally a manual drum brake car. I added a factory booster,master cylinder,metering valve, combination distribution/proportioning valve and calipers. Brakes worked great since the install and pedal bleeding 500+ miles ago. Noticed a leak on the passenger side caliper and found the piston seal was leaking. Replaced the caliper and cannot remove the air out of the system. All connections are tight and dry. Pulled MC from booster and no leaks out of the MC piston. The MC gets a little wet but not from the lines. Fluid seems to push past the lid gasket. I might just have too much fluid in the bowl. I can gravity bleed all the air out then try to pedal bleed and air starts again. The pedal bleed pattern is; very small foamy bubbles followed by a couple larger 1/4" ones. This repeats,repeats,repeats and never stops/ I have run through more than 48 ounce of the same Valvoline DOT3 as I used originally. Gravity bled again and have a very mushy pedal. Rebuilt MC Summit (A1) and calipers (Autozone). Has anyone run across this and have any ideas?

 

[wedge69]

Did you Bench Bleed the master ?
If Not you are going to have alot of air in the system till you do.

 

[Dako]

Since I don't see it mentioned in your post, I gotta ask...You are re-bleeding ALL wheels again, not just the caliper you replaced, correct?

 

[Photon440]

Have you tried a vacuum brake bleeder? Works the fastest for me.
http://www.princessauto.com/pal/en/...n/Vacuum-Pump-And-Brake-Bleeder-Kit/8050832.p

 

[rm6p]

Yes, master was bench bled and has worked great for 500+ miles. That is what has thrown me.

 

[rm6p]

No, Just the replaced caliper. Pulled hard line at the hose connection and capped immediately with minimum fluid loss. Reverse on install. Hose and caliper were mounted before hardline. Hardline was uncapped and installed again with minimum fluid loss. I would estimate fluid loss at most,a couple inches of hardline, total, removal and installation. I have pedal bled much more air than could ever have been in the hardline. I gravity bleed and after a while the bubbles stop, I pedal bleed and the bubbles start.That is the puzzle. I agree that a soft pedal would require all 4 corners to be bled but, there is not an end to the air bubbles at the problem caliper. It is like I am manufacturing air somehow, somewhere without the telltale sign of a fluid leak. The brakes worked great when I pulled the car into the garage. No sign whatsoever there was a problem while driving. The drip on the caliper was my clue to investigate, not the drivability. That said, I will probably vacuum bleed all 4 tomorrow.

- - - Updated - - -

I will try vacuum bleeding all 4 in the morning. Thanks

 

[mopar12372]

the hydraulic line from the frame to the caliper could be leakin at the caliper copper seals . try tightning or replacing them

 

[rm6p]

Dako, You were absolutely correct about bleeding All wheels. By looking at the amount of fluid that was lost disconnecting/reconnecting the brake line I was floored when bubbles came out of every wheel cylinder and caliper. This old car stops like a Viper now. I will not make that mistake again. Thank you very much for the simple eloquent statement above. That will be my mantra any time the brake system is opened regardless of the fluid loss. BLEED ALL WHEELS, BLEED ALL WHEELS..........Thank you again

 

[Dako]

rm6p,

As fluid leaves an open line, that little bit of air gets displaced along the top (above the remaining fluid). Because the lines are so small, that air can cover great distance. I'm glad you were able to get everything right.

 

[rm6p]

Dako, Thank you again..What a relief to have brakes..