What am I doing wrong? (Brake Question)

The vehicle has drums on all four corners? If so, was the shoes friction material for each ground to the exact circumference of the drum? In other words, does the entire shoe face contact the drum? Reading up on drums brakes from back in the day it is best the shoes entire face contact the entire drum surface for good stopping and good pedal feel.

We went through this with a 52 Buick. Bench bled until the cows came home. Bled the cylinders umpteen times. Poor stopping and pedal. Not until the shoes settling in making good contact with the drums did the pedal become firm and stopping ability as it should.

 

Did you try swapping the lines at the master cylinder front to back? I seem to remember some MC had a built-in timing issue to make sure the brakes applied in the proper order (front first?). This was done through a combination of where the seal surfaces were on the pistons and where the outlet ports were in the casting. But everything I can remember says that the rear port should go to the front brakes on master cylinder like that.

 

^^^^^^^^^^^^
That's how I am planning to plumb mine Shaun....sorry I should've wrote that in you build thread.

 

Might have to look into a larger MC then..

It is a new MC, I can't remember for sure, but it's most likely something imported.. The cap has the "accordian" style rubber in it, and that seems to be working (when we bleed the brakes, the little rubber cup will be pulled down).

 

The original master cylinder had a vented cap...if your new MC has no breather that's why you loose pedal after bleeding. The fluid must be able to get back into the master cylinder after bleeding!

 

I agree that the only thing line size will affect is velocity, plus fluid volume on initial fill. All the rest is BS on line size.
The shoes not being ground to fit drums could have an effect to a small degree on sponginess when pedal is pushed really hard, hard enough to actually flex the shoes or other parts. What it will affect is actual braking power of the brake drum/shoe assembly in question. Careful driving and frequent brake application, being careful to not overheat, will soon seat them in. In years long gone by I worked in a full sevice parts house and radius ground lots of shoes to fit the drums. For rivetted linings we also had a composite shim stock to place between the shoe and lining to compensate for larger drum ID from turning drum. I have asbestosis today from what I suspect is all the dust from grinding linings. We also had bulk woven lining that came in rolls where you selected the proper width, cut to length, drilled and counterbored for rivets and rivetted to shoe, and various molded lining minus holes to drill & counterbore to fit.
What hasn't been mentioned is reverse bleeding, where fluid is pumped in thru the bleeder valve at the cylinder to force the air out back at the master cylinder, which in your case is the highest point in the system, and the natural escape route for air. Didn't work too well on my under floor master cylinder when I tried it, and my best results were/are with speed bleeder valves which allow the air out at the wheel cylinders just like normal bleeding, but easier to do alone.

 

Try adjusting the brakes on all four wheels until they are TIGHT (drum won't turn) the bleed the brakes using standard procedure. If there are no problems with the master cylinder and all wheel cylinders you should get a solid pedal. Then back off all wheel adjusters until you get the proper drag. verify the master is properly vented.

 

I type slow, pretty close to post #37..A few brake posts ago Dick S brought up that the adjusters [42-48] should be out locking the wheels for bleeding, takes up any slack in the old/new parts..Once bleed and there is pedal you then back off the adjusters to the slight drag at each wheel..The 1" Bore MC should be fine as it actually moves more fluid than a single MC at same amount of stroke... Gravity bleeding works suprisingly well; pump the pedal a few times then crack a bleeder and give the pedal a little stab to get things started and be sure to not let the MC run out and leave cover off, just cover to keep dirt out..

 

willys 1>>>You can block (fab some plugs) off the master cylinder where the lines attach, and, with no air in the cylinder the pedal should be rock hard and high.>>>

El Rat>>>As above...block off the MC to prove or disprove the Integrity of the unit. When you completely block off the MC it will be rock hard, >>>

I'm still waiting for the results of these suggestions. I think the NAPA description suggests a core with all new innards, pistons, springs, etc. Doesn't necessarily mean the bore of the core was honed properly. Could be leaking past the primary cup. Do these simple tests to eliminate this possibility if you haven't already. Report back.

Thanks

Jack E/NJ

 

I have the accordian style MC gasket... Should there be a hole in the gasket as well?

I just registered the car today, so hopefully I can try to run it a little more to try and wear them in... There are several roads near the shop with little traffic and few houses, so I can test it pretty safely. Will also have to look into reverse bleeding... Had thought that might be a good way to try it

I'll give this a try as well and see what I come up with...

 

If your MC does not have residual pressure valves build in, add them in the lines (10 pound RPVs for drum brakes).

If your MC does happen have them and you add others in the lines, it won't hurt anything.

 

The 52 Buick I spoke about, a few post back, was driven and had the same complaint. No pedal and stopping sucked. Keep your distance when driving. What happened for him after some drive time(100 miles) the pedal became firm and braking much more pronounced. His pedal was originally just off the floor. Once he shoes settled in and the entire face was making contact to the drum did the pedal become normal. He spent hours replacing, studying bore size, tried new MC, rebuild MC, new lines, new hoses, checked width of the shoes 100 times and bleeding the entire system like mad. Shoes just needed to get happy with the drums.

 

I have 39 Ford brakes on my Model A with a 1" Mustang drum-drum manual master cylinder. I had the rear port closest to the pedal rod going to rear brakes.
If I adjusted the brakes to just drag,the rears would lock and the fronts would be loose. I adjusted the rears loose and it worked ok.

I read on an early mustang forum that the rear port was the primary port and the first to get pressure. I hooked the fronts to the rear port and have had good brakes for several years.

Switching ports might help.

John

 

Do you meant to say that Q =AV and P=F/A still hold true ?? !!

 

showoff!!!!!!!!!!!!!!

 

Alright, found the plugs that came with the master cylinder tonight and tested the MC.

Plugged both ports, and the pedal was rock solid- that eliminates the MC being junk I guess...

While the lines were off the MC, I also reversed them just to rule that out. The rear port (closest to pedal) now goes to the front brakes, and front port goes to rear brakes.

Bled the lines again, and saw no real improvement from before...

This afternoon I drove the car around 10 miles (before I tested the MC, and swapped the lines around).. I was able to stop, but it did require a few pumps for it to work- not really ideal..

Perhaps I just need to wait for the shoes to wear in though?? Sounds like the car 54Buick worked on had really similar issues... Only thing is that my pedal will still actually go all the way to the floor

 

I forgot to ask, how do I check to see if the MC has RPV's built into it??

 

Well they would be sitting behind the seats in the MC ports. I don't think you'd be able to see them. A way you could check although it's not fool proof is depress the brakes, then crack a wheel cylinder open. If some fluid comes out then there's some residual pressure in there.

 

isnt the rear port in a dual master cylinder for the Front brakes?, but on a Drum/Drum setup it probably dosent matter?

 

I switched my lines around, and that is how I have them now.

 

I
Adjusting '39-'42 Brakes: This is from a collection of tips sent to me from "rumble seat"
I used to hate these brakes because of the adjustable double anchor when I was a mechanic in the mid fifties. Then a fellow mechanic showed me a Ford Service bulletin. Ever since then, I have preferred these to the '46-'48 units since I can get a better adjustment.
These are Lockheed brakes which use eccentric washers in conjunction with non-eccentric anchor pins to position the shoes. The top of the shoe is controlled by an eccentric cam (usually 11/16") located near the top of the shoe. The anchor pins, located at the bottom of the backing plate, control the shoe position by turning the eccentric washers at the bottom of the shoe. These anchor pins have locating on the elongated 1/4" adjuster. The locating marks may be a dot or an arrow, I'm assuming everything is in good condition and not rusty or frozen.
Step 1: Loosen the anchor pin large lock nuts (usually 3/4") on both shoes of one wheel just barley enough to permit turning the 1/4" anchor pin adjusters. Now, turn both of the 1/4" adjusters so the locator marks face directly towards each other. This next point is important .... All further adjustments are made by turning the anchor pins (1/4") and eccentric (11/16") downwards.
Step 2: Back off the upper eccentric cam adjusters on both shoes until the wheel rotates freely.
Step 3: Now turn one of the upper eccentric (11/16") until the wheel cannot be turned.
Step 4: Now turn it's 1/4" anchor pin adjuster downward until the wheel just turns freely. This lowers the shoe and moves the toe of the shoe away from the drum and results in fuller shoe contact.
Step 5: Now go back to Step 3 and do it and step 4 again to the same shoe. Repeat as necessary until turning the 1/4" anchor pin adjuster will no longer free up the wheel. Back off both anchor pin adjuster and upper eccentric just enough so the wheel has a slight drag. Tighten the anchor pin lock nut (3/4") without letting the anchor pin adjuster move. Now do the other shoe the same way.



If you've worn the shoes badly at the top, it'll take some time to wear the heel enough so you get full brake shoe contact.
When adjusting brakes, always turn the wheel in the same direction the wheel would turn when the car travels forward.
PS: The 1/4" anchor adjustment bolts require an offset open end wrench about 8 1/2" in length to get enough leverage to turn, I think it's a special Ford tool and hard to find. BillB


Further information from Richard (EV8G) 0:17AM 09/11/2007
I wrote about this "awhile back" but the way time flies, it could have been this year, or last, or??? You can read the link shown in the post above, and you can read the Ford Service Bulletin.
Adjusting the upper hex bolts to set shoe clearance is the easy part. The confusing part is the lower anchors on 39-42's. The Service Bulletin sends you through a procedure to follow, but does not explain why or what needs to be achieved.
The purpose of the lower anchors, which are eccentrics, is to properly position/center the linings in the drums, so that full lining contact can occur. OF FIRST IMPORTANCE is to have the new linings arc ground to fit the arc of the drums, which may be different on each drum, depending on the oversize of the drum. If this is not done, you are rolling the dice on whether the lining is too large of an arc (and will only contact the drum at the ends) or too small (and will only contact the drum at the center of the lining)- in either case, full contact cannot occur regardless of the anchor adjustment. Note also that the lower anchor adjustment is only required when installing new linings.
Once the anchor studs are set and the lock nuts are tightened, the shoes will not move out of center with the drums, and thereafter only the upper adjustment need be performed to compensate for lining wear.
In a nutshell, assemble the anchors with the dots facing each other as a starting point. Make sure that the drum turns freely, then adjust the uppers until they don't, then back them off until they do.
Have a helper apply about 30lbs of pressure to the brake pedal while (with the lock nut loosened) turning the flat on the anchor stud in each direction to cause the lining to impact the drum in both directions, then set the anchor in about the middle of that travel, hold the stud while tightening the lock nut. This essentially centers the lining up/down in the drum, allowing it to make full contact
when the brakes are applied. This operation is done to each anchor/shoe/lining separately. When all have been done, again adjust the upper (clearance) hex heads until the shoes are just barely off of the drums.
Road test and readjust as necessary to make it stop good and straight.
It is also important to have at least 1/16" of free travel of the Mcyl pushrod before it starts moving the Mcyl piston; otherwise, the brakes will not fully release, will get hot and will lock up.
The above is not exactly the same procedure as provided elsewhere, but it is what I do and it seems to work well. If you keep in mind what you are trying to accomplish, it makes sense.


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Since the master cylinder held solid with the plugs in I would suggest leaving in the plug to the front brake port. Now hook up the rear brake line and bleed the rears. If you can maintain pedal with the front plugged the problem should be in the front half. Hook the fronts back up and if the pedal is gone then you know the problem is between the master and front drums and every thing else is good.

 

If you have two adjusters (or 4) for each wheel you must have a proper brake adjustment or you will never effect a proper bleeding procedure. The brake shoe need to make equal contact all around the drum. If you are adjusting the minor adjuster to get drag, even if you can't turn the wheel you may have a situation where the heal of one shoe ad the toe of another are contactig the drum and preventing it from turning but when you then apply pressure by the pedal, you are still not really forcing the shoes into full contact with the drums. then when you think you are done, and retract the adjusters you are causing a situation where the travel is greater that when you were doing the bleeding and the pedal gets spongy or has to travel further durig brakig than during the bleeding process.

Also re check your hard ware, make sure the rods between the wheel cylinders and the brake shoes are the same length as the ones that you replaced. and or the internal pistons are the same length as the ones you took off. Go to the Graham Paige club website. In their tech or repair section is a tool you can make to assure both brake shoes are centered and concentric to the drums and adjusted to have full contact along their friction surface.

If you are good with a caliper you can take an interior measurement of the brake drum, figure the recommended clearance, set the tool to that measurement and effect a proper concentric adjustment before you put the drums on.

Also an old timer once showed me a trick for stubborn bleeding problems. With the shoes off, place a suitable clamp (bodyman's vice grips work) clamp the wheel cylinder so it can not push the actuating rods and bleed that line, then reinstall the shoes springs, do the process above, put the drum on and than bleed it again. Long way to go but you really need a good proper adjustment prior to a bleedig session.

 

Alright, I tried this today and I think I've found the problem...

I adjust all the shoes all the way out so the drum was tight- the wheel would not spin at all.

Climbed in the car, and had a solid pedal! Must be from shoe adjustment being off, if it was air it would have still been spungy....

I'll back the shoes off just a little and drive it like that to try and wear them into the drums some more, I think that should take care of my problem.

 

Yes sir, these old drum brakes love to have the entire shoe touching the surface of the drum. They will improve as the shoe arch matches the drum circumference.

 

Told ya so! Glad it worked for you. When the shoes wear and are in need of another adjustment, the pedal will let you know.

 

Yup, kudos to you guys (and the other that helped)!

I've made a couple trips, adjusting the brakes each time when I come back, to where they're dragging somewhat on the drums. Each time the brakes seems to be getting a littttle bit better- an improvement over yesterday for sure.

 

Just a note:my 37 coupe had always seemed a little spongy--ever after 30 years of driving and a few brake repairs. I helped a friend do a bke repair not long ago, and he bought some of those"speed bleeders". We installed them--and damn! They worked great! I ordered some for mine--couldn't hurt,I figured. Put them in--what a difference! In 10 minutes, the pedal felt much better---so I'm sure that air trapped in the system has been a problem--it doesn't take much air to cause a problem--just my .02!