Rear brakes getting hot, front cold.

[Jack Shultz]

Hi all, new to FBBO. I like the site and it is very informative. I have a 71 Road Runner with factory 11x3/11x2.5 manual drum brakes. My rear brakes get very hot after a short drive. Been this way ever since I had the car on the road. I backed off on the rear adjustment and this helps some what. The e-brake adjustment is very loose and the function is good. My system only has a distribution block with warning light terminal. All parts are new on this car except this block. I am wondering if maybe the valve in the block might be stuck and is blocking fluid to the front brakes. The fronts do work if I jack the front up and spin the wheel. But I can't tell how much I am getting under load. Overall, the car does not have a lot of braking power. Is there a way I can tell if my valve is off center? (the light on the dash is not lit) included are pics from when I built the car.

 

[Rusty knuckles]

Sounds like it. I'd change it. Assuming brake lines are new too? Slave cylinders and brake shoes all match? Possible to have a blockage as well.

I have a manual drum brake charger and while it won't win any stopping contests it doesn't feel like I'm short braking power. But I do have to push hard.

 

[64BEL]

I would check the fronts for adjustment. They may need to be adjusted tighter. Stopping with the wheels off the ground doesn't tell you much, as you said. How's your pedal? Does it push down far under braking? If so, I'd say the fronts aren't adjusted tight enough. And if the rears are getting hot, I'd suspect they're still too tight. Do the rears spin freely when the wheels are off the ground? Also, are you sure the shoes are installed correctly - large shoe in the back?

 

[CoronetDarter]

Had the same thing on my Coronet after getting back on the road. The rear brakes would get so hot I couldn't touch the lug nuts.
Turns out when I replaced the master cylinder and brake booster I adjusted the m/c rod incorrectly and it was bottoming out in the power booster, slightly engaging the brakes full time. Readjusted the brake rod and it's been all good since.

 

[mtbase]

Just "spit balling" here:
Has anyone messed with the lines going to the MC? Is it possible that the lines are reversed?

 

[AR67GTX]

Did you also change out the rubber hose feeding the line splitter block on the differential?

 

[dadsbee]

'tis what my (booster) Bee use to do before restoration if I didn't lift the brake pedal up with my toe after a stop. With you having manual brakes however that adjustment clearance isn't an option, but your pedal could be binding. Try lifting the pedal after stopping. It is NOT your distribution block...

 

[Jack Shultz]

Had the same thing on my Coronet after getting back on the road. The rear brakes would get so hot I couldn't touch the lug nuts.
Turns out when I replaced the master cylinder and brake booster I adjusted the m/c rod incorrectly and it was bottoming out in the power booster, slightly engaging the brakes full time. Readjusted the brake rod and it's been all good since.

Yes, that happens a lot on

Sounds like it. I'd change it. Assuming brake lines are new too? Slave cylinders and brake shoes all match? Possible to have a blockage as well.

I have a manual drum brake charger and while it won't win any stopping contests it doesn't feel like I'm short braking power. But I do have to push hard.

'tis what my (booster) Bee use to do before restoration if I didn't lift the brake pedal up with my toe after a stop. With you having manual brakes however that adjustment clearance isn't an option, but your pedal could be binding. Try lifting the pedal after stopping. It is NOT your distribution block...

'tis what my (booster) Bee use to do before restoration if I didn't lift the brake pedal up with my toe after a stop. With you having manual brakes however that adjustment clearance isn't an option, but your pedal could be binding. Try lifting the pedal after stopping. It is NOT your distribution block...

Actually, I put a bungee cord on the pedal to test that theroy. No change.

 

[Jack Shultz]

Sounds like it. I'd change it. Assuming brake lines are new too? Slave cylinders and brake shoes all match? Possible to have a blockage as well.

I have a manual drum brake charger and while it won't win any stopping contests it doesn't feel like I'm short braking power. But I do have to push hard.

All new except the distribution block.

 

[Jack Shultz]

Just "spit balling" here:
Has anyone messed with the lines going to the MC? Is it possible that the lines are reversed?

Anything is possable, but I am starting to think I might have a disc/drum master cyl. Both resvoirs should be the same size. Mine are not.

 

[Jack Shultz]

'tis what my (booster) Bee use to do before restoration if I didn't lift the brake pedal up with my toe after a stop. With you having manual brakes however that adjustment clearance isn't an option, but your pedal could be binding. Try lifting the pedal after stopping. It is NOT your distribution block...

I tried a bungee cord on it just to make sure. no change.

 

[Jack Shultz]

Sounds like it. I'd change it. Assuming brake lines are new too? Slave cylinders and brake shoes all match? Possible to have a blockage as well.

I have a manual drum brake charger and while it won't win any stopping contests it doesn't feel like I'm short braking power. But I do have to push hard.

The brakes are always free. I think I may have a wrong master cyl. Doing research.

 

[Jack Shultz]

I would check the fronts for adjustment. They may need to be adjusted tighter. Stopping with the wheels off the ground doesn't tell you much, as you said. How's your pedal? Does it push down far under braking? If so, I'd say the fronts aren't adjusted tight enough. And if the rears are getting hot, I'd suspect they're still too tight. Do the rears spin freely when the wheels are off the ground? Also, are you sure the shoes are installed correctly - large shoe in the back?

Adjustment is good on the front. slight drag. Shoes are on correctly, adjusters are on the right sides. Rears spin real free. I am researching master cyl. I may have one for disc drum.

 

[Jack Shultz]

Did you also change out the rubber hose feeding the line splitter block on the differential?

 

[Jack Shultz]

Brand new, and checked it too before I installed.

 

[Jack Shultz]

Did you also change out the rubber hose feeding the line splitter block on the differential?

yes

 

[Jack Shultz]

Had a long conversation with a mopar restoration friend. He asked me a ton of questions. He looked at the car and he thinks I have the incorrect master cyl. He thinks the one I need has both resivoirs the same size. Mine has one big one for the front and a small one for the back. Anyone out there have a Manual Drum Drum that can take a picture of your master cyl?

 

[Jack Shultz]

According to this article, I do have an incorrect master cylinder on my car. I have the correct one coming. I will post results once it is installed. https://therammaninc.com/files/cate...uide_to_Mopar_Master_Cylinders_1967-19746.pdf

 

[Jack Shultz]

Well, here is where I am at with the hot rear brakes. After 10 miles of driving, rear brakes are hot, front are cold. Again, non power brakes, 11x3 front drum, 11x2.5 rear drum. I have changed to the correct master cyl according to all info in the FSM. (Bore size and equal size pots) I have replaced the factory proportioning valve with a new one from Inline Tube. (I know it is not a proportion valve, the FSM calls it that though) I have cleaned out all the lines by removing the bleeders and pushing clean fluid through all, No flow problems to front or rear. I also hooked my mighty vac to the lines at the master cyl and pulled fluid the from each wheel with hose on the bleeder onto a bottle of brake fluid. No flow problems. I put a gauge on the one front brake cyl and have 1200 psi. (I do not have an adapter small enough to check a rear brake pressure) The e-brake is free and the spreader bar is loose without pressure. The shoes are retracting all the way to the top pin without problem. After driving, I jack the back of the car up and wheels spin freely. I have the adjusters backed off pretty far at the rear and adjusted up pretty tight at the front. All the shoes and springs are installed properly according to the FSM. The adjusters are on the proper sides and work properly. As of right now the passenger rear is about 120 degrees hotter than the driver rear. (260 vs 140 using a laser thermometer) Also, somewhere in this mix, I have replaced the rear wheel bearings following the FSM to the letter. Now, to boot, My brother is having almost the same issue with his 67 Chrysler Newport. It is just his passenger rear wheel though. All he did was replace the shoes.

 

[oldbee]

There’s only a couple more possibilities. Out of round drums, different friction coefficient on the shoes themselves?( I don’t really believe in QC anymore)