1966 Mustang Coupe, 1988 5.0 HO, T5z, EFI, MAF, 4 wheel disc w/ booster

How should the brake pedal feel after a bleeding w/ a brake booster installed?  My pedal still feels soft. I can definitely drop it to the floor w/ ease.  And I know that's not supposed to happen.  Car isn't running yet so I can't test the brake booster as there isn't a vacuum on it.  I'm trying to narrow down the problems.  I checked all the connections and didn't see any leaks.  I even did a reverse brake bleeding to get all the air out of the line.  I know the most likely culprit of soft pedal is air in the line or leaks... I'll triple check everything but does anyone know how or if the break booster could play a part?  I have a proportioning valve installed from when the rear brakes were still drums.  Could that be a factor?

Update - 11/21/2018

Still chasing air in the line.  Really getting frustrated.
-Car has not been driven in 7 years.  Long term restoration project.
-2 years ago I did a front disc converstion w/ SSBC kit.
-Did the rear brake converstion w/ Summit racing kit last month. 
-2 chamber fluid brake fluid resevoir.
-Don't see any fluid leaks.

* tried to bleed all 4 wheels in correct order, still have soft pedal.
* Never got air out of the front brake lines
* Bleed master cylinder through front left caliper.  still soft pedal but stiffer
* Went back to rear wheels and bleed again.  a little stiffer pedal
* Went back to front wheels and pedal went soft again and still air in the line.
* Pulled master cylinder and did a bench bleed. Some air in MC, not a lot.
* Bleed wheels again, Pedal still soft, still got air in front brake lines.
* Pulled front wheels and checked fittings, Driverside brake line fitting to hose cracked so I replaced it.  Tightened up everything and bleed front brakes again. STILL have air in the line but pedal seems stiffer, doesn't bottom out.  (progress?)

Will pull rear wheels today and re-re-re check all fittings to rear brakes.  Car hasn't been driven so MC has only seen work by way of bleeding interaction.  It was new from the SSBC Kit and seemed fine when I did the bench bleed.  Possible MC is faulty but I doubt it.  Don't want to pay $80 but check if MC is the problem.   I'm running out of ideas.  Where the heck could this air be coming from?  NO WAY this much air was in the line after bleeding all 4 wheels and doing a bench bleed.  I've also tried gravety bleeding, and reverse injection bleeding.

I have this crazy idea of drilling a small hole in the MC over and mounting a air pressure barb.  Then use some zip ties to make sure the cap forms a good seal on the master cylinder.  Next I can put ~25lbs of air pressure in the master cylinder resevoir and that would force fluid out at the leak point.  This seems drastic.  Any of you old timers think of a better way to track down  leak in the system?


Update - 12/3/2018

Good news: I have wheel locking brakes!  The car isn't running so I can't truly test them yet but with the pedal depresessed I couldn't turn any of the wheels w/ all my weight trying to rotate them.  E-brake is adjusted to the point of the rear wheels locking as well.  No air in any of the brake lines when bleeding.  Brake pedal is firm.  Seems like my problem was the rear e-brake wasn't adjusted correctly causing their to be too much travel in the rear calipers leading to the spongy feeling.

The bad news: I feel like I have too much pedal travel.  I have to press the pedal all the way down to get a hard stop.  I'm not sure how wrong this is because my only point of reference is modern cars.  Also, w/ the car not running and no vaccumm I can't check the impact of power brakes.  I'm looking into what pedal adjustment options I have if any.


thanks

Last edited by TremendousWand (12/03/2018 8:12 AM)