I Would Try to BLEED the Master cylinder First!
Try Pumping the Brake Pedal 4/5 times Hold Pedal down Bleed the R/R First! Then L/R Then R/F Then L/f

Hopes this helps ..Or try to locate a Vac Bleeder that Sucks the Brake fluid through the System or A Power Bleeded..Thats What I Used When I Had My Shop!

good luck