You replace the wheel cylinders ?
Loosen the threads at each junction Starting at the MC
And have someone mash the pedal and see if it squirts out 
If it does, move on to the next one 
That way you can isolate where the blockage is 
The rubber lines swell up inside 
Or there may be rust or some thing blocking a line 
You just have to me methodical and logical in finding it 
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