Hydraulic brake pull to left

Bob Johnson

Bob Johnson

Well-known member
This is one of the reasons I do not prefer hydraulic brakes. My pickup has 38-41 brakes on the wheels. It has a 1960s dual piston master cylinder. It has always pulled very slightly to the left. However recently there is a strong pull to the left. I checked the front wheel brake cylinders and neither one had fluid coming out of the rubber boots. There was no fluid on the brake shoes or lining. However upon opening up the rubber boots there was a small amount of rusty fluid (water + brake fluid). I replaced both front brake cylinders (for the forth time since I got the pickup) and it still pulls hard to the left. I have not checked the rear brake cylinders but they are located at the bottom of the backing plates and I do not see any fluid dripping from the bottom of the backing plates. I decided to see if I could find out which wheel is not braking (it should be one on the right side?). I put the pickup on jack stands and held the brake pedal down until the brakes started to hold. I could not tell any difference in the four wheels when I manually rotated the wheels. As I put more pressure on the brake pedal all four wheels required about the same amount of pressure to move the wheels. They also locked up at about the same time. I will likely check the two rear brake cylinders. But other than a skid test (it pulls real hard to the left and a skid test might be dangerous) is there any other way to find the weak wheel? I do not want to go back to mechanical brakes at this time $$$$
Bob
 
Have you adjusted the brakes?? Have you replaced the hoses?? #9-42 brake adjustment is "finicky" and must be done in sequence.
Paul in CT
 
The hoses look OK. I just adjusted the cams that move the shoes in and out. That helped a lot. Thanks Paul. It still pulls slightly to the left when I first apply the brakes. But if I back off then re-apply the brakes it stops straight. That is similar to what it was like before. Anyone have any suggestions for why it pulls left when the brakes are first applied but straightens up after backing off and re-applying the brake ?


Bob
 
Do the two cylinders at the master go to left-right or front-rear?

My only experience with hydraulic brakes on a Model A was years ago. I remember that they pulled hard to one side before I adjusted them. I think there is adjustment at the fixed ends of the shoes in addition to the cams, although I could be wrong as it was a lifetime ago.

It sounds like something is sticking and I would look first at the wheel cylinders. Can you take the drums off and watch the action at the shoes while someone else steps on the brake pedal?
 
The master cylinder has the fronts and back on separate pistons. both front and back are Ford equipment. The fronts are the later ones without the adjustment at the ends of the shoes. The rears have the end adjustment.
 
Bob : Had the same problem on a
dual M.S , the M.S did not have the
residual valves which holds 10 lbs.
pressure on brake lines.

Jim
 
Your right brake hose has swollen to near shut. Replace both of the brake hoses. The brake hose may look good from the outside but it has deteriorated on the inside. This is a common problem.
 
SSsssteamer said:
Your right brake hose has swollen to near shut. Replace both of the brake hoses. The brake hose may look good from the outside but it has deteriorated on the inside. This is a common problem.
Click to expand...

Yep! That's what I was thinking except why the rubber hoses weren't changed with the wheel clylinders ?
 
SSsssteamer said:
Your right brake hose has swollen to near shut. Replace both of the brake hoses. The brake hose may look good from the outside but it has deteriorated on the inside. This is a common problem.
Click to expand...

Ditto. It's probably a good idea to also replace the rear hose while you're at it.
 
It sounds like there may be a little dampness on the shoes??? Alsop check to see if the short shoes are at the rear, opposite of Bendix brakes. I use DOT 5 silicone fluid, it rejects moisture and the cylinders last much longer.
 
With functional hydraulics, all wheel cylinders react the same amount and at the same pressure. It's just the physics of it. Where problems usually happen is shoe to drum fit and proper adjustment of that. There can also be a problem when one drum is at max limits of wear and another is at minimum. It's hard to adjust for max wear. Lockheed type brakes work but were never as good as the Bendix design where both shoes provide effective braking.

The model A in stock form has the disadvantage of the rear suspension being in the way of the wheel cylinder on top set up. Many folks modify the backing plate to rotate the wheel cylinder forward of the spring location and some mount them upside down. I always wondered about the effects of either way of mounting as to whether one way is better than the other and my conclusion is that neither way is perfect but both can function to some degree. I would prefer the wheel cylinder closer to the top than the bottom. It has advantages in the way hydraulics work for fluid flow and return.

My conclusion with it all is that the mechanical design in good working order is the better way unless a person installs a Lincoln set up with full floating shoes.
 
Usually the first thing I do after buying a collector type car is go through the brake system,the brake hoses can and do collapse on the inside, if I am not sure of the age or condition ,change them out, lost brakes on a 39 Buick years ago shortly after purchase,so l am some what paranoid on brake systems.Did get the 39 stopped but was quite an experience.
 
SSsssteamer said:
Your right brake hose has swollen to near shut. Replace both of the brake hoses. The brake hose may look good from the outside but it has deteriorated on the inside. This is a common problem.
Click to expand...

Agree!
My Studebaker hoses looked good, but one was blocked internally.
 
Bob, I have also had a steel brake line clogged with corrosion as well. It may be a combination of both. In my situation I had to change both hard and rubber lines along with flushing the system and changing the fluid. Marc
 
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