FACTS:
The car is my '65 Satellite which I converted from single to dual circuit brakes (all drums). I installed a bench-bled remanufactured Bendix MC, the original pushrod and pedal. All the brake lines are new from InLine Tube. The three flex hoses are new. None of the brake cylinders leak, but the fronts are new & the rears were the ones I bought the car with. The brass distribution block is from a '67 Belvedere and I installed correct hydraulic nipples at the MC, spiraled the lines to the block, and double-checked the install against Ehrenberg's tech article in Mopar Action April 2004.

PROBLEM;
If the car has sat overnight and I take it for a drive, the rear driver's side wheel locks up really really easily. Scary. The rest of the brakes have little action, if any. But after about 4-5 full stops, this problem goes away and I can spend the rest of the day with completely normal braking, evenly balanced on all four wheels.

I'm cautious during those first few stops. I come to a full stop and pump the snot out of the pedal. After the first few stops, it brakes evenly without lock-up even under heavy braking.

What on earth could cause this?

Something changes or is corrected in the first 5 minutes of driving and braking?

The car can sit for hours after that first drive, and will still be fine. Some air "bleeds back" when sitting for 8-10 hours?

NOTES:
- The pedal does harden up a bit when I pump it, meaning there could be some air somewhere, but I've bled the @!#^%@ out of the MC and every line, in the correct sequence.

- After a good drive and I can feel that the rear wheel temperature is hotter than the fronts, which tells me that the rears are working more (or dragging?) than the fronts. Why? Don' the fronts "work harder" than the rears?

- The shoe-advance mechanisms seem to be working fine. But this is something I could double-check. (I had asymmetrical rear braking on my '67 which I traced to a stuck advance mechanism, but that was a permanent condition during a drive, it didn't go away after the first few minutes).

IDEAS:
1. - Check the rear shoe advance mechanisms.

2. - Check all four brake cylinders? - nothing leaks but I replaced the fronts with new. The original rears were fine, so I cleaned them up and reused them. These are one difference betw front & rears.

3. - Could air be trapped in the front brake MC circuit that goes away? I've already had the MC out once to pump and re-bench-bleed. PITA. But can air still be trapped in the MC after 400+ miles of driving, and bleeding of the brake lines?

4. - Take the car out tomorrow and, when the brakes have evened out, brake until I get a lock up and see if the rears or fronts lock first, just to get clarity how well the fronts are working. Kinda pointless, but it might reveal …something?

Thanks for reading and thanks for any insights.
- Art

They need adjustment, the drums need you to back up and hit them several time. It'll take a short time for them to adjust...if they have auto adjusters. Tim

Hey Art is this the brakes from Hell issue from last year . First I'd get ALL the air out one way or the other then spoon the linings up fairly tight/even on all 4 corners & see where you're at. EDIT If one side (dr in this case) pulls/locks up then the opposite (pass) side ain't pulling it's share of the (braking) load so concentrate on the pass side once the air is out (if there is still a problem)

that is odd that it goes away, but I too believe I would try the adjusters first.

back off the one that locks up easy and see if this is still repeatable.

I like to take them to the point where I cannot turn the wheel and then back off the adjuster till I can. I try to count the number of pulls I use to back off the adjuster so I can set each wheel to the same place. kind of ocd about that.

Make sure the brake shoes are free of oil and the parking brake lever is not partially engaged.

I would replace the unknown; rear wheel cylinders. If one had a bad hone job you could have a myriad of strange issues. DAMHIK. Same goes for master cylinders!

Make sure you have the long shoe mounted toward the rear of the car, short shoe toward front. Very simple and basic, I know, but often overlooked. Make sure you don't have two long shoes on one side and two short on the other. I have seen both, many times. Also try bleeding with a hose from the bleeder screw to a see through bottle of brake fluid.
jess

Many years in the auto service industry and I've seen this issue in several Import and Domestic models both passenger car and light trucks. Strangely enough, none have ever brought them in with that complaint wanting to have that "issue" addressed/fixed.
The most recent was in a '02 Mitsubishi Montero Sport ( drum rear ) the first few brake applications were, as you said, scary. The slightest braking would result in a severe locking up of the rear brakes, and I mean just touching the brake pedal. The cars are typically left overnight for other repairs and the locking issue would diminish by the time we pulled them into the service bay. The thought would be "I'm sure I can sell a rear brake job on this one" to our surprise that on inspection, no excessive/visible/easy to sell/ wear is ever noticed.
I say all this to let you know that it's not too rare of an issue. Most people get used to it and don't want to spend the money to fix it. That being said, my guess would be drum and shoe diameter difference exceeding specs or maybe no chamfer on the friction materials edge if you don't find anything obvious. I would be very surprised if it were a hydraulic issue.
Sorry that I can't offer a solution. I will be watching for others smarter than me to chime in with the "Fix".

Try sanding the shoess and drums a bit.Do it lightly and then hit them with some brake clean.Do both sides and see what happens.My 57 Chrysler would do pretty much the same thing even with new shoes.Its pretty much free except some time.After you do it readjust the shoes also.Rocky

Thanks so much for your input guys -

RRobert, thankfully no, the brakes from He** were on the '67 which turned out to be inoperative advance on one rear side (to be specific, the cable to the advance "blade" got hung up at the top centering post, making it too short to affect the advancer's cog wheel).

Copper Dart,

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The most recent was in a '02 Mitsubishi Montero Sport ( drum rear ) the first few brake applications were, as you said, scary. The slightest braking would result in a severe locking up of the rear brakes, and I mean just touching the brake pedal. The cars are typically left overnight for other repairs and the locking issue would diminish by the time we pulled them into the service bay… I say all this to let you know that it's not too rare of an issue.

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Thanks this is a precise description of my problem. SUPER sensitive. But just on one side. Then it goes away. I know you don't have a solution, but thanks for informing me I am not alone, LOL.

I took the car out this morning and it takes no more than 2-3 brake applications for the problem to go away.

I'll start investigating the rear passenger side (opposite the one that locks), and see if the shoe is retarded too far off the drum, if shoe sizes are oriented correctly, then maybe replace the rear brake cylinders. I'll post pics if I see something worth sharing.

Now if I can just get a babysitter for my three boys this afternoon….
- Art

Art...I'll assume you have the shoes in their correct positions primary/secondary, that the master is a dual tandem drum/drum master, and the system is properly bleed, and that all 4 wheels are properly adjusted, when you adjusted the brakes manually, did you occassional step on the brake pedal to "center" the shoes in the drum?....if not try that

I have seen conditions where the shoes are initially contacting only the outer edge of the shoes lining, because either the drums aren't cut deep enough in depth to fit the shoes, or the shoes have the friction material installed/overlapping too close to the edge...which can result in erratic pedal/braking issues.....you need to "read" what the surface/wear condition is on the shoes/drums to either isolate it to a wheel(s) before going off in to searching for other causes

Mike

Thanks guys, I'll do some thorough cleaning.

Thanks Mike,
No, I didn't center with the pedal during reassembly. I typically eye-ball the advance screw and cog wheel, and try making the shoes as equally advanced as possible before sliding the drums on.

Final manual shoe advance was done with the drums on and that's when I would get in the car and check the brake pedal felt reasonably hard.
I think I'll repeat the shoe advance adjustment process.

And thanks - I'll check for any unusual wear pattern on the pads.

A condition that could cause my symptom is if three-of-four brake cylinders were sticking every time the car sat for 10+ hours. The one "good" cylinder gets all the pressure the first time, then the other three cylinders become unstuck after the first applications of brake and they all work fine after that.

With more info yes it sure ain't air & as said find out what part is hanging up/sticking part time

Thanks Mike, got it.!
I'll get into it this week and report back.

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Art, so there's no confusion on either behalf,

With the drum off, adjust the star adjuster so the pads are out as much as possible to allow the drum to fit, attach drum/wheel assy, then pump the pedal once to center the shoes, while turning/rotating/spinning the wheel/drum (fronts with wheel off ok, rears need the wheel bolted on, or a nut(s) hold the drum in place, I prefer the wheels on) adjust the brakes with an adjuster "spoon" until you just hear a slight contact, then pump the brakes again to further center the shoes, spin the wheel/drum assy again until you hear slight contact, then repeat, pump/spin/adjust until the contact is barely heard/felt and any amount of pumping and centering the brake shoes yeilds the same results, then proceed to the next wheel...then road test, see what you get?

FYI, it's your choice, but back in the day when I worked in the shop, common practice on drum brake install was to bevel the outer edge of the shoes linings with a quick pass of a grinder so that the linings would make full contact with the drum(s) rather than the edge of the lining, which after it quickly wore would result in some of the issues you've mentioned, just thought I'd mention it so you can save the time of pulling the wheels again...

Mike

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Here's the update on this situation:

The asymmetrical rear braking problem basically disappeared by itself over the course of driving the car the past several months.
Too bad I couldn't determine a specific cause. The problem just got less and less, now it doesn't do it anymore, even after sitting 10 days or so.
The "pedal feel" could be a bit better, so tomorrow I'm re-bleeding the brakes and will hopefully just move on to enjoying the car.

Cheers,
- Art