JBugs Video Series

Bleeding Brakes after Disc Brake Conversion:

Video Overview:

We're finally ready to bleed the four disc brake conversion on our 1963 Resto Custom Beetle. Bleeding the brake system completely of air is the most important step to ensuring safe stops. We use a vacuum bleeder first and follow with the old fashion pump and hold method to evacuate the air from the hydraulic system. Note that when bleeding disc brake calipers it may be required to rotate the calipers so that the brake bleeder valves are at the top. If you do not feel comfortable bleeding your brakes or can not get a consistent and firm brake pedal we recommend taking your VW to a qualified professional.

Video Tips:

Tools you will need:

Vacuum Brake Bleeder
8mm Wrench
13mm Wrench
Side Cutters

Chemicals used:

DOT 3 Brake Fluid
Brake Cleaner

Video Transcript:

Hello there, I'm Sam with JBugs.com. We're finally finishing up our four wheel disc brake conversion for our 1963 Resto Custom Beetle. We are going to be bleeding our brake system which is nearly all new.


Getting all of the air out of the master cylinder, lines, hoses, brake calipers, and wheel cylinders is crucial to ensure safe stops. More often than not, any problem after installing new brake components are attributed to not completely bleeding the brake system. If you cannot get a consistent and firm pedal, we recommend taking your car into a mechanic.


We have our beetle up on jack stands at the front and the rear and all four wheels are off so that we can access the calipers and bleeder valves. To start, because we have installed a new master cylinder, we need to adjust the length of the brake pedal push rod. We use a wrench to unlock the brake pedal push rod and adjust the length of the push rod so that there is less than an inch of free play in the before the push rod engages the master cylinder.


Most books recommend five to seven millimeters of play but I prefer a little bit more. Regardless, make sure that there is some play in the pedal. If there isn't any free play, the brakes will have pressure applied all the time, keeping the brake lights on and applying brake pressure to the pads or shoes. With the adjustment set, the push rod is held and the lock nut is threaded down and tightened against the pedal boss to prevent the rod from loosening.


Next, we fill up the brake fluid reservoir with fresh DOT3 brake fluid. We use the upper reservoir to fill the lower reservoir. Our gas tank is out, so we can see when the fluid has reached the top of the lower reservoir. If your tank is in place, an assistant can be handy to let you know when the fluid in the lower reservoir has reached the top. Because the lower reservoir has a vented cap, it is important not to overfill it. The upper reservoir is more or less a permanently mounted funnel. It is used to fill the lower reservoir only, not to hold any additional fluid.


Inside the car, press the brake pedal a few times to begin feeding fluid to the master cylinder. After making sure the brake fluid reservoir is full, we start the bleeding process at the right rear brake caliper which is the farthest from the master cylinder. We use a vacuum pump to suck the fluid through the line. It's a much easier method of getting most of the air removed from the lines, especially when starting with a new brake system.


At the right rear, the bleeder cap is popped off the bleeder valve and a closed end wrench is slid onto the valve. The bleeder adapter from the vacuum pump is pressed onto the valve and held in place with light pressure to ensure a tight seal. A dab of grease can help to make sure the adapter has an airtight seal. The pump is squeezed to put about fifteen inches of vacuum on the gauge. As long as the needle does not move, we have an air tight seal and can proceed. The bleeder valve is opened about a quarter turn and the pump is squeezed to keep a vacuum on the line. It will take some time for the brake fluid to get pulled through as the master cylinder and brake lines are empty. Eventually though, a steady stream of fluid will come through the line and start to fill the cup.


Position the bleeder adapter vertically and keep pumping the vacuum until no air bubbles appear in the line.

Check the brake fluid reservoir and fill it up if necessary.

The same process is repeated at the left rear caliper.

The brake fluid level is checked and filled if needed.

The front right caliper is bled with the pump.

Again, check the brake fluid.


Finally, the left front caliper is bled with the pump. Once all four calipers have been initially bled, an assistant is needed to finish up the bleeding process as we bleed the system manually with the calipers rotated to ensure the bleeders are at the top of the pistons.


At the right rear, the upper caliper bolt is loosened; the lower bolt is removed along with any spacers if used. The caliper is rotated up and we use a wrench in between the brake pads to hold the caliper up and ensure that the pads aren't pressed out when the pedal is pushed. A wrench is slid onto the valve again. We use the brake bleeder adapter, hose, and tank from the vacuum pump and press it onto the valve vertically and hold it in place to prevent any leaks.


Inside, our assistant pumps the pedal a few times to build pressure, then holds firm pressure on the pedal while the brake bleeder valve is opened a quarter turn then closed when the fluid stops flowing.


This process is repeated a few times until no air bubbles appear when the valve is open. The brake caliper is bolted back in place; making sure to put the spacer or spacers in place if they were used. The brake fluid level is checked and topped off if needed. The same process of rotating the caliper up and bleeding it manually is done at the left rear until no air bubbles appear.

The caliper is bolted back in place.

The brake fluid level is checked again.


The front right caliper is unbolted from the spindle and rotated up on the brake rotor until the brake bleeder valve is at the top of the piston. Again, the manual bleeding process is done until no air bubbles appear.

The caliper is bolted back to the spindle.

The brake fluid is topped off again if needed.

The left caliper is unbolted, rotated up, and bled using the same process.

With all the air bled from the front left caliper, [it's] bolted back to the spindle and the bleeding process is complete.


The brake pedal should have a positive feel and should operate with the same feel every time the pedal is pressed. Check the brake fluid level one last time. Make sure the bleeder valve caps are popped in place at all four calipers.


Clean all the brake rotors, calipers, and pads with brake cleaner. Check all the hose and brake line fittings for any signs of fluid leaking. Tighten the lines or if need be, repair or replace them. If there was a leak, you may have to bleed the brakes again. If you replaced the line, you will have to bleed the brake system again.


Finally, check the brake pedal feel. It should feel the same as it did earlier. If the pedal seems to have dropped or requires pumping to get a firm pedal feel, there is still air in the system. The manual bleeding process will have to be done again.


We're done with our system and have completely changed the look of the car, with the lowered front and rear suspension. Most importantly, we've vastly improved the stopping power and safety with the disc brakes. We hope you've enjoyed this portion of our Resto Custom Beetle rebuilding process. Stay tuned as we will be showing more of the restoration soon. Thanks for watching and be sure to click on JBugs.com for all your vintage Volkswagen brake and suspension parts and accessories.