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Elated Technician
Elated Technician, ASE Advanced Master Technician
Category: Car
Satisfied Customers: 486
Experience:  16 yrs exp, Auto/Diesel Associates degree, ASE Master w/ Advanced cert, Saab Master and BMW level 4
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54 Ford: retro fit a power disc brake system..pedal..parking space

Resolved Question:

I have retro fit a power disc brake system onto my 54 Ford truck. The front are disc and the rear are drum. I lose pedal when backing or making a hard left on the wheel as you would when backing into a parking space, say at a car show with a perfect 32 deuce behind you. YIPES! I have been thru three master cylinders, and have installed the Wilwood check valves in line. Always the same result. Pedal goes to the floor when backing and making a hard left. I can actually get it to go to the floor parked if I crank the wheel hard and mash the pedal. I am baffled. I have been struggling with this for three years and my mechanic finally asked me not to bring it back. Any suggestions???
Submitted: 8 years ago.
Category: Car
Expert:  Elated Technician replied 8 years ago.

Thanks for all the good information on your concern. I have a few questions to help isolate the issue.

When you are backing up in a straight line, do you have a brake issue, or only on left turns when backing up?

What type of brake hoses do you use? Are the DOT 5 (silicone) compatable?

Are all the brake components DOT 5 compatible?

Have you noticed any fluid leaks, or do you think the fluid is bypassing the master cylinder?

Do you suspect the brake pedal is flexing at all?


Customer: replied 8 years ago.

The lines are stainless, the hoses are standard issue Autozone. But if hoses were the issue would they not fail when the vehicle was moving forward. Backin out of the driveway or backing straight never seems to be an issue. I have taken it out in a parking lot and tried to get them to fail. They will lock up and skid under hard braking in forward or reverse. She has not been topped up since I bled the brakes 3 months ago and I have not lost any fluid. It is a pleasure vehicle and I always check the floor and tires for leaks that may show up but there is never anything but a drop or two from the oil pan plug. I would not know anything about fluid bypassing the master??? or brake pedal flexing either. Remember this is a 54. The master is under the cab below the drivers seat and the pedal is not a swing type but an uncomfortable downward arc to the master below the cab. It is a pretty solid piece of iron as they built them in 54. I cannot imagine it flexing they way it is built and mounted.

Thanks Jason,


Expert:  Elated Technician replied 8 years ago.
Hey Keith,

Thanks again for the great details on your brake system. I assume you went to DOT 5 because it will not damage paint if it is spilled.

A few of the concerns with DOT 5 is that it does not have the lubricity of regular glycol based DOT 3 and 4. This may be effecting you proportioning valve under certain situations. It also does not absorb moisture as well and needs to be flushed sooner to avoid moisture build up and boiling (every 2 years for DOT 3 and 4). DOT 5 will also areate easier if it is shook. I wonder if the reservoir allows it to splash and basically pump air into the brake system under certain situations. Does the rubber cover/seal come down to meet the fluid level to avoid areation?

Also, is the master a dual circuit? I have read of some cases where the front circuit does not engage fully if the pushrod is not long enough. This can effectively reduce braking effect to the rear (?) (even though you can lock up the front brakes) .

Another idea I have is if the calipers are flexing on the mounts or the brake pads or rear shoes are compressing (if there is any corrosion it may be compressing under load) or compensating for the torque of the shoes on the backing plate. I would think this is a greater concern since one rear wheel has more torque applied in a turning situation. The brake shoes may be twisting so much that it causes more fluid flow due to the extra slave movement in the reverse direction.

I hope these ideas are helpful in resolving your concern. It sounds like a fun project to keep up with.


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Customer: replied 8 years ago.

The pushrod is adjustable, maybe I need to give it a little more length. i will try that tomorrow. I am sorry I ever started with Dot 5 do I need to replace any components or can i just flush it through with 3 or 4?