NO BRAKES, Peddle goes to the floor

Master cylinder needs replacing .

brakes pads go with calipers and disc brakes,brake shoes go with drum brakes which has wheel cylinders.

Unless you have a leak in the brake system the only reason your brake fluid level master cylinder would be empty is that your brake pads are worn out. As they wear the fluid level goes down. You need to check for a leak at all 4 wheels and the complete system. If you find no leak then inspect all brake pads and replace as necessary. I would also bleed the brakes as you let the fluid get very low. More than likely a new set of brake pads will solve your problem. The only thing that is suspicious is the clunk you heard. Make sure a trusted mechanic gives your brake system a good inspection. It can be very dangerous if your brakes fail.

when you bled the lines ,Did you start from the wheel farthest from the resevoir?

Normally when the brake pedal goes almos to the floor it is an indication of low brake fluid. Low brake fluid is an indication that front and/or rear brakes are wearing. As the brake pads wear down more brake fluid will be required in the wheel cylinders or calipers. Hint, the front brakes usually wear much faster than the rear due to the fact that the fronts due a much greater braking function that the rear. Check the front pads. Don't let them get down to the metal scraping metal stage before you change them out. This causes unnessary damage to the rotors. Look at your master cylinder on the firewall under the hood in front of the steering wheel. If the fluid level is belowhte "max" mark add fluid. Low fliud should also show as a red "brake" light on your dash, but not always.

no they are inverted flare fittings no seals check all lines and calipers/wheel cylinders if all are dry remove the vacuum hose from the booster if there is brake fluid in the hose the master cylinder is bad

I just went to Brake Masters this morning and had them replace the Master Cylinder since I was experiencing the pedal very spongy and going to the floor. When they replaced the Master Cylinder and they gave me back the car, the brakes were still spongy and going to the floor. I addressed this to them and they took another look at it, but when I took it for a second time, the brakes were extremely spongy. It was almost like they gave me back my car in worst condition to when I brought it in. Can you help?

bleed the brake again. if the pedal goes to the floor with little resistance, then the master cylinder is your problem.
the shim is to depress the noise when you applied the brake. you can skip that, if the brake works without it.

Did you bench bleed the master cyl. before installing it? then when you installed the new master, did you bleed all 4 points? If yes, then check all for points for leaking caliper/s and leaking wheel cylinder/s. If the van has ABS, check the valve body for a bleeder screw and see if air bleeds out of it. If you've checked everything twice and did everything right then your new master cyl. may be defective.

change dump valve under master cylinder