1969 dual circuit Brake bleeding
I am having a bear of a time bleeding the brake system on a 1969 GTV and I am wondering if anyone can post some experience with good bleeding technique. My main problem is that I cannot get a consistent pedal feel, and I think I still have air in the system...though I can't be sure what the actual problem is for sure. With the car not running (no boost) I have to pump the pedal a few times to get good pressure, but it will almost always bleed down and pedal goes to the floor. With the engine running (boost on) it does a similar thing.
The car has had quite a bit of brake work in the past few days:
New front calipers.
Newly rebuilt master cylinder.
New Boosters (from Classic Alfa).
Originally the car had a very sticky and inconsistent brake pedal feel. It also would on occasion get a lock up of the front brakes (after releasing the pedal). New front calipers and boosters seem to have gotten rid of those two issues but then I choose to rebuild the master because it had a slight seap. I found a high quality rebuild kit which I sourced from Jon Norman and the cylinder was in pretty nice shape internally. There are no leaks in the system anymore and I've tried all bleed methods:
Power bleed at 15psi.
Vacuum bleeding at each caliper
Vacuum bleeding at the reservoir
Cracking open the lines at each booster (under pedal pressure)
Cracking open the lines at the master (under pedal pressure)
Tapping on all components
My only doubt is that I possibly still have a master cylinder issue because when I pump the brakes and build pressure, I can hear a "whishing" sound coming from inside the master.Maybe it is air returning to the reservoir? or maybe my rebuild failed?
NO luck! I am defeated. Help!
PS: I believe I have read every "1969" brake bleeding thread on here haha.
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Last edited by vespam5; 09-18-2019 at 09:12 PM.