Albert, the master cylinder has a front and rear chamber. Make sure the rear chamber has brake fluid in it. It's best to pressure bleed the brake calipers instead of pumping the brakes manually which can damage the master cylinder. Start by using a turkey baster to remove old brake fluid from the master cylinder then refilling with new brake fluid. Then be sure to maintain the fluid level so as not to introduce air into the brake system.

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Fred Hoelzle