Car Brake lines have no pressure?

First inspect if there is brake fluid or not.If the fluid is low,then add brake fluid.
But if after adding brake fluid,still brake lines have no pressure,then more troubleshooting is required.
When the master cylinder [just below the plastic reservoir where you added the fluid] goes empty, air gets in it. Since air can be compressed [unlike liquids] the system does not generate any pressure. You may have to bleed the entire brake system to get the air out. Before you go to all that trouble, there is a short cut you can try. Have someone watch the fluid reservoir [with cap removed] for air bubbles while you gently press the brake pedal about 1/2 way down and release it. This will allow the air trapped in the master cylinder to escape upwards. Repeat until no bubbles are seen in the reservoir and you have a firm pedal. This trick may require up to 50 pumps of the pedal. The truck must be on level ground or with the front of the truck slightly above the rear.
Did you find any brake fluid on the ground? If so, you must fix that leak. If no fluid was found on the ground, then the leak is the rear seal of the master cylinder. The fluid gets sucked into the power brake booster [big, black metal can behind the master cylinder], then into the engine and out the exhaust. If this is the case, you need to replace the master cylinder to fix the leak. Follow the instructions which will come with the replacement master cylinder to "bench" bleed it prior to installation.
This details will help.Thanks.----------------------


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