Brake issues

[72HCODE]

it is really hard to balance the drums.

If the car brakes hard to one side then the opposite side is suspect.

so if the car is turning right when braking then the issue is with the left side.

most balance issues are caused from the rear brakes.

my car tends to go left when heavy braking. i kept playing with the rear right drum and one mechanic told me to leave it alone for a while and see if the shoe breaks in, you know the car isn't going straight but sometimes it needs to be driven for a while to wear in the shoe...

the issue i have is i have a traction lock rear diff, the traction lock makes it impossible to balance the rear brakes left to right because i cannot feel how much drag each drum has. usually you can jack the car up put it in neutral and then with an open diff you can spin each tire and feel or hear the drum shoe drag on the cover. i kept-ed messing around with the adjusters and i might of been chasing my tail. so I'm driving the car carefully hoping to see if the stronger rear brake will wear in if i leave things alone. each time i take the car out i drive in reverse at about 10mph and slam the brakes that is suppose to automatically increment the sprocket adjusters in the drums.

Another thing to check that people get mixed up is putting the automatic adjusters on the wrong side of the car.

if that happens then each time the brakes re-adjust the drums loosen not tighten and eventually you loose rear brakes completely.

one last thing that can throw off brakes is a bent frame, or bad alignment on the front end. caster angle can be out of balance left to right and cause stopping issues.

 

[Manu Mach1]

Thanks guys for all of your informations, for today I give up, only for today, I will be more fresh tomorrow.

I will check first the soft ones, then step by step as you mentionned above.

Thanks again.

 

[MeZapU]

I had a problem with my car locking up the rear wheels even under light braking. I went through a similar amount of troubleshooting such as you are doing. All new rubber hoses. Inspected every inch of the hard line to ensure there were no kinks or smashed sections. I installed a Willwood adjustable proportioning valve with no improvement. I finally figured out that my axle shafts were bent causing the wheels to wobble and the brake drums along with them. I purchased and installed some used but straight axle shafts and it cured my problem.


And also ensure on the drum brakes that the primary and secondary brake shoes are in their proper orientation. I've seen them reversed and even having each types of shoe(both primary or secondary) on the same side of the car.

 

[rocket366]

Good Call!

I guess we take it for granted knowing that the tall shoes to the rear!

 

[72HCODE]

another thing that occurred to me as far as brake balance with rear drums:

how worn out is the drum backing plate, there are 6 pads on each backing plate that can wear out and groove many people forget you must grease these pads for proper operation.

now as an example: this is NOT a 71-73 mustang backing plate however the grease pads are in the same spots.

these pads wear out, groove and cause rear brakes to make noise, grab and even lockup.

I don't think the backing plates are reproduced and getting them repaired can be a big deal because they have to be welded on then the spots ground flat again.

 

[Omie01]

I had to do this to mine, I welded the pads up and ground them flush and smooth. If anybody wants me to do this for them, just PM me and we can discuss it.

 

[mrmach1]

There are two things on a car I don't fool with and I want working perfectly one is Tires and two are the brakes. I would take it to a professional and not skimp to save a few bucks. Just my opinion for what it's worth. I value my life and the life of others to much to do otherwise.

I totally agree with you, but here to find a professional to work on this old car is not easy, only garage where they connect the computer to tell you that you have to change this or that, and most of the time the prblem is coming from something else, but still you have to pay for what you didn't need.

If I knew a guy who would spend time to analyse where is my brake issue, I wasn't here to share with you guys.

Sorry about that I forget your not here in the States we still have a lot of old school wrench turns who will work on these old cars and in fact they prefer too. I hope you get some help from the forum for this problem. Much luck.

 

[72HCODE]

i would say with everything if you do suspect the prop valve then replace it with one of the reproduction ones, this way you would have an unmolested part to compare things to. if you install it and the problem stops then mystery solved.

if the problem keeps going then you know you must look elsewhere.

some people end up with cars that were originally front drum or manual brakes and they get converted to power disc/drum in the process things get overlooked. incorrect booster or master cylinder, incorrect push rod length, original manual brake pedal assembly, wrong prop valve. on the 60s models you could of even gotten the wrong spindles installed which led to handling issues.

point is even the top mechanic might never be able to sort out what the problem is and just call a car possessed because they never put together enough information about what is going wrong.

it is very possible that in the past somebody messed around with the prop valve, either to rebuild it or to clean it out and didn't know all the details about reassembly. any time i questioned a part i replaced it just to be safe or to have a comparison. i'm still learning all the time since the devil is in the details.

now with the prop valve the way it works is the front disc brakes get full pressure all the time. the top half of the prop valve has no restriction basically the master line come through the top and the 2 side feeds front goes to the drivers side and back goes to the passenger side around the back of the engine on the firewall.

the brake light switch sits between the disc and drum system and if there is a leak on one side then the piston inside moves and triggers off the sensor which lights the dash telling you the system is out of balance.

on the bottom end of the prop valve is a pressure valve with heavy spring. this assembly has a large amount of adjustment built in.

that valve controls the amount of pressure going to the rear drums and how fast they engage.

now normally when a prop valve fails the fluid gets cut off the rear drums and you can see it when you try and bleed the rear wheel cylinders as nothing comes out or very little.

when people rebuild the prop valve they take apart the spring valve and change the seals, then they put it together, and possibly they assemble it wrong.

in that case it turns into an adjustable prop valve because it is either engaging the drums early or later. you have no real way of measuring the pressure because the adjustment is internal to the prop valve, so that would mean, taking the prop apart popping the bottom nut over and over, using a screw driver to adjust the spring valve then assembling the prop valve and rebleeding the entire system over and over until you get it right, forget it you know that won't happen. at that point either replace the prop valve with a known good one or go with an adjustable valve with external adjustment that you can mess around with and get just right as you drive the car.

 

[Manu Mach1]

Yesterday I bleed of the entire system, fluid was coming out very easy.

After flushed the right rear then the left rear, I did the front right. While doing this I was always keeping the contact as I could see if the brake light was on.

And then I could hear the prop valve moving then the brake light was on, only when I was bleeding of the front right. Then I finished with the front left, try the car and still have the same problem.

Here are pics about the rear brakes, if you see anything wrong...





But why do I have more pressure in the right brakes than in the left?

Next step is to unscrew the rear brake sprocket adjuster and see what happen.

Also I checked the 6 pads on each backing plate and they are ok and greased.

 

[RacerX]

In the top picture of your left side, the wheel cylinder cup looks wet with brake fluid, indicating a leak. Might be a stuck piston and not applying, there by applying no brakes on left side and all brakes on right.

 

[Manu Mach1]

Looks wet but was just me who removed the dust with finger.

My problem is still not solved, waiting for the copper grommets that wasn't delivered with a set of new soft hoses.

Coming soon.

 

[Don C]

Have you checked the runout on the rotors and the roundness of the brake drums? Also the runout of all 4 wheels?

Another outside possibility is alignment on both the front wheels and rear end of the car. Are the front bearings adjusted properly, any loose steering system components?

 

[Manu Mach1]

"are the adjusters set too tight, if you back them off a couple of clicks it would reduce the rear brakes engaging early"? from 72Hcode.

Well, I did it, and I have more brakes in the front. In the meantime I received some new soft hoses for the front, even if they were correct, not bad to change them.

So I can say that my problem is solved, thank you again to share and give advice.