Master Brake Cylinder For 46-66 Jeep & Willys
Brake Service: Check List
- Check fluid levels in the Master Brake Cylinder: Fluid should be to a level 1/2″ below the top of the fill hole. Use only heavy-duty brake fluid that conforms to the specification SAE-70-R3.
- Check brake pedal adjustment: There should be at least a 1/2″ free pedal travel before the push rod engages the master cylinder piston. Adjust the brake pedal by shortening or lengthening the brake master cylinder eye bolt.
- Check brake pedal play: If the pedal travels more than halfway to the floorboard, the brakes may need adjusting. First check to see that the brake pedal has 1/2″ free travel. Lift up the wheels to clear the floor. Rotate the brake shoe eccentric. Use a wrench to loosen the lock nut for the forward brake shoe, hold the lock nut and with brake wrench turn the eccentric towards the front of the vehicle until the brake shoes strike the drum, then while turning the wheel with one hand release the eccentric until the wheel turns freely. Hold the eccentric in position and fasten the lock nut. Repeat these instructions to adjust the reverse shoe, only turn the eccentric towards the back of the vehicle. Check the fluid level on the master cylinder after all four brakes are done.
- Check tire pressure after adjusting if the brakes pull to one side: Tire pressure should be 26 psi for the front and 28 psi for the rear. Correct tire pressure ensures even braking. If the brakes still pull to one side check the brake lining for foreign material and clean if possible. If cleaning does not correct this issue replace the linings. Check front wheel alignment and balance if side pull persists.
- Check brake system for leaks: Apply steady pressure on the brake pedal to see if it falls away which would indicate a leak. If the pedal fall away check for the leaking wheel cylinder. This is done by removing the wheels and drums and carefully checking each cylinder. Also check all lines and fittings. If the leak has allowed brake fluid to get on the linings, the linings will have to be replaced.
- Check pressure of hydraulic system: If “spongy” this can be corrected by bleeding the brakes. If the fuel line has been disconnected or air has gotten into the lines the brakes must be bled. The system must be free from air at all times. Begin bleeding by starting at the wheel with the longest line from the master cylinder, the next longest second, etc. Keep the hydraulic brake fluid level of the master cylinder at least 3/4 full during the bleeding. Carefully clean all dirt from around the master cylinder filler plug. Remove the filler plug and fill the master cylinder to the lower edge of the filler neck. Clean all bleeder connections of all four wheel cylinders. Attach the bleeder hose and fixture to the right rear wheel cylinder bleeder screw and place end of the tube in a glass jar, and submerged in brake fluid. Open the bleeder valve 1/2 to 3/4 of a turn. Depress the foot pedal, letting it to return very slowly. Continue this pumping action to force the fluid through the line and out of the bleeder hose which carries with it any air in the system. When bubbles cease to appear at the end of the bleeder hose, close the bleeder valve and remove the hose. Repeat this at each wheel cylinder and after that has been completed, fill the master cylinder reservoir and replace the filler plug. Dispose of all used brake fluids, the fluids cannot be reused due to air bubbles and dirt.
- If brakes are locked and the vehicle cannot be moved, open the bleeder screw on any of the wheel cylinders this should release the brakes. This may be caused by a defective master cylinder or the use of low grade brake fluid which has expanded because of heat.
This comprehensive Build Your Willys YouTube video shows the steps on how to remove your worn out sloppy master brake cylinder.
In order to remove your old worn out master cylinder first, be sure to disconnect all brake lines from the master cylinder. Inside the frame of the willys jeep, remove the cotter pin from the pedal shaft next to the brake pedal arm. To disconnect the master cylinder tie bar, loosen the master cylinder then free the Tie bar from the cross shaft. Remove the cotter pin, master cylinder eye bolt and washer from the brake pedal. Slide the brake pedal arm off of the pedal cross shaft. Next, remove the bolts from the frame. Remove the Brake master cylinder assembly.
Comes complete with boot. For early frame mounted vehicles. Both mounting holes are unthreaded.
Call Mike @Kaiserwillys.com for details at TOLL FREE 1-888-648-4923 (Mon-Fri, 9AM-5PM EST).
New Master Brake Cylinder – Part#: 805223
Q: Is there a hole in the floor board to get to the master cylinder to put fluid in?
- A: Some models have a access hole. Some don’t. We do carry a cover part number#: 7697522 that you can install.
Q: Rebuilding an M38A1 1954. Original master cylinder is sloppy. Are kits dependable or should I replace?
- A: The master cylinder repair kits are a good option but the bore on your old master cylinder needs to be smooth. I always try to steer people towards this new master cylinder. It’s just a lot easier and new.
To watch other videos on the disassembly of your Willys Jeep Vehicle refer to The Build Your Willys series on YouTube. Order the Service Manual For The Universal Jeep Vehicles, includes complete vehicle disassembly, assembly, and blowup diagrams.
*EMAIL or call Mike Toll Free (1-888-648-4923) Mon-Fri, 9am-5pm EST if you have any questions about this part or restoring your Willys.