Front Brake Locks

[vandie12]

69 Charger drum brakes, new brakes, drums, master cylinder, booster. Brakes have all been bled air seems to be out, adjusted brakes all the way around. Everytime I step on the brakes I have the front passenger side brake lock  up before the other brakes. Need some advice on what the problem could be. 

[Chryco Psycho]

is there any grease or oil residue on the shoes , are the shoes new or old ?

[vandie12]

All new, no grease or residue.

[bull]

Probably a bad RF wheel cylinder.

[vandie12]

Bull, I've thought the same thing but wasnt sure what could go bad with it that would cause the lock up. As soon as I hit the brakes going 5 mph the right front locks up and skids the tire, let the pedal up and its ok. Could there be an issue with springs? I took the wheel apart and checked everything out and it all looks good, I even backed that brake off but no difference.

[FLG]

Could be a bad drum, friend of mine had an issue with a brand new drum that was out of round. Try swapping to the other side and seeing if it still locks up.

[vandie12]

I checked it by spinning it and seeing if rubbed on the shoes and it didnt rub at all spun nice and free...

[bull]

If the plungers weren't retracting as far as they should (due to a weak spring, corroded cylinder walls, whatever), and you bled the system with that cylinder stuck open, just tapping the brakes would make that wheel lock up. As far as backing them off all the way? I don't if you can back them off enough to keep this from happening if the wheel cylinder plungers are stuck. Not saying you can't, just saying I don't know. At any rate I am willing to gamble your $12 that it's the wheel cylinder.

[vandie12]

Well Bull you owe me 12 bucks, put a new wheel cylinder on and still locks up.........

[FLG]

His spun freely too...try it on the other side and see if it locks up.

[vandie12]

I will tommarow, tried everything else on the side that skids maybe there is an issue of not enough fluid going to the other side that does not skid......... Any ideas from anyone will help......

[bull]

Well Bull you owe me 12 bucks, put a new wheel cylinder on and still locks up.........

  How about a beer?

[vandie12]

Switch drums.......... same issue........  Need more than 1 beer........

[bull]

So what was it doing before you replaced all this stuff? Was it working fine then? Did you mess around with the proportioning valve?

[vandie12]

The brakes, drums and it looks like the wheel cylinders were all replaced before we got the car a year and a half ago. Everything was taken off when we did the complete resto job. Put it back all together only difference was we added a power brake boster and new MC, didnt take the wheel cyl apart. Kept the drum brakes all the way around so we didnt need to replace prop valve or so i thought.  Thinking back we drove the car around a little before resto job and it mite have already been pulling to the right. The right wheel cyl that I took off and pulled apart a couple of days looked like it had been put on new but over the years of sitting had quite a bit of junk inside. I'm wondering if the other wheel is the same and and will pull that off also and take apart.  Didnt do anything with the prop valve.

[charger Downunder]

69 Charger drum brakes, new brakes, drums, master cylinder, booster. Brakes have all been bled air seems to be out, adjusted brakes all the way around. Everytime I step on the brakes I have the front passenger side brake lock  up before the other brakes. Need some advice on what the problem could be. 

Can you back off the adjuster or adjust it a bit on the one that locks up first.

[maxwellwedge]

Do you have a drum brake master? Are the front and rear halves the same size (drums) or is the rear of the master a different size than the front (disc)?

[Musicman]

I would swap all of your front brake components (everything but the mounting plate itself) from left to right and vice versa. If the problem remains on the right side, then you'll know you have a plumbing issue. If the problem moves to the left side you have a component issue, which can be narrowed down by swapping left to right again one piece at a time.

By the way, the proportioning valve has nothing to do with front brake operation.

[1BAD68]

I had a 70 years ago with that problem but on the drivers front.
turned out to be the rubber brake line wasn't installed correctly, had too tight of a bend in it.
I replaced the line and lock up went away.

[vandie12]

   Thanks everyone for your input, I think I have in narrowed down, will change out the front brake cyl. on the driver side also. Took it off and found a lot of junk, lesson learned just because it looks good on the out side doesnt mean its good on the inside. Will keep all updated as soon as I get the new one installed.  "Bull", I owe you 2 beers.

[bull]

Sweet! I'll take 'em.

[bull]

By the way, the proportioning valve has nothing to do with front brake operation.

It does if you've got next to nothing going to the back, which is possible with an adjustable one. Were you thinking dsitribution valve?

[Musicman]

It does if you've got next to nothing going to the back, which is possible with an adjustable one. Were you thinking dsitribution valve?

Bull

Contrary to popular belief, Proportioning valves are not In-Line Restrictors, or Fixed Pressure Regulators. They are a pressure sensitive reactionary device designed to adjust braking force under abnormal braking conditions.

Under normal braking conditions, a poppet piston is held in a relaxed position by a large pressure spring. The poppet valve is held against a retainer by a light return spring, and fluid passes freely through the valve to the rear brakes.

In heavy braking, master cylinder pressure can reach a valve’s crack-point. The pressure applied to the 2 different areas of the poppet piston creates unequal forces. That moves the poppet piston against the large pressure spring. This action holds the conical section of the valve against the seat, which limits the pressure increase to the rear brakes.

As greater pedal force increases pressure in the master cylinder, fluid pressure rises on the smaller end of the piston. This combines with the force of the pressure spring to overcome the lower pressure now on the larger end. This forces the piston back, clear of the poppet valve.

The increased pressure now acts on the larger end of the poppet piston and again forces the piston forward to contact the valve.

When the pedal is released, the pressure of the rear brake fluid unseats the poppet valve, letting fluid return to the master cylinder. The pressure spring now returns the poppet piston to its relaxed position.


Found this for you... It's a bit of a read but good information on the subject of all these mysterious brake system components, and how they work. Much better than my quicky explanation, and it has pic's too!:
http://www.studebaker-info.org/tech/brakes/bf50014.html

[bull]

 

[Paul G]

Brake hoses have been known to come apart on the inside when they get old. Could actually create a blockage. If they are old I would consider replacing them. The left front could be blocking fluid flow. Try having some one lightly apply the brake with the drums off and make sure you see the wheel cylinder pistons move out. Other thing is, are all the springs installed in the correct places?