1969 RR 4 wheel drum brakes. New master and booster. I know I do not make enough vacuum to have a reliable booster. My issue is that everything is new. Drums cylinders shoes hardware hoses. Now when cold the car stops as it should. Has maybe a little extra pedal travel. Now once it gets hot when I barely touch the brakes the front right completly locks up. I was going about 10 mph in my drive way and checked this visually. I dont understand why my front right is locking up when hot. Please help as I want to drive it this summer and it is not safe right now.

since it is only the RF it would have to be downstream from the T in the line out to the front brakes. we'll assume the hose ain't collapsing with it being new so I would open up the drum & check things out & check wheel bearing torque. I would also check booster rod clearance for the excessive pedal travel along with shoes to drum clearances. EDIT long(er) shot, a shoe hanging up on the 6 backing plate contact pads, you want em fairly smooth with no deep grooves. I'd adj the pushrod (want ~.020")/adj the shoes, all of em/check wheel bearing torque & good visual inside the drum on the RF that is locking up.

Check the shoe adjustment. If that wheel is adjusted up tighter than the others it will lock up first.

Also check for contamination on the shoes themselves. If they somehow got grease or oil on them they will grab.

When you say "hot" are you referring to the engine or the brakes themselves?

If it's the engine, once it's warmed up it probably makes a little more vacuum so your booster has a little more to work with.

If it's a new/reman booster it might also have a calibration problem itself. There is a valve inside them that allows them to be progressive. I've had a booster that as soon as you touched the pedal it went to full boost and put your face in the windshield. If you have uneven shoe adjustment it would lock up one wheel before the others.

Kevin

When you take off the drum, look at everything for any clues. Uneven contact, drum slightly out of round, any sign of where it's grabbing.

There's some good brake tech from Chrysler in the MTSC pamphlets.
The Imperial Club has almost all of them on line.
go to www.imperialclub.org -> Literature -> Master Technicians Conference
Scroll down to the 1960s and 70s for drum brakes closest to your year.
1969 is the first year for the new revised self-adjuster hardware and shoes.

I had this happen with my Coronet. I did a complete 4 wheel brake job one summer all the way down to new brake lines. The car drove great all summer but when I took it out of storage the next summer the car would dive to the right. I took the drums off and noticed the right front shoes were dis-colored. I replaced the shoes and haven't had a problem since. It's been 9 years now. I'm not sure what got on the shoes, maybe something on my hands when I installed them? Maybe they were contaminated when I bought them? But I never found any hydraulic leaks.

Is wheel barring adjusted right?... It can do it, I had it happen to me but most of the time after you go up road in back after it warms up.. a out of round drum may can do it also!

Remember,,,BIG to the back!

Long shoe in back and short one in front? Possible bad or crushed brake line or hoses.
Also is the self adjuster installed the correct way?

Contamination is a possibility, pull drum and check shoes, wipe with brake kleen.

post what it ends up being.

Is the Adjuster in right ??/

Thanks for all the input. This seems way more logical than master cylinder or vacuum issues. I am going to check it out on Tuesday i will post what I find.

I chased brake problems for a solid year on my blue Hornet. When I went through the brakes the first time, everything was dry, so I figured I'd save a buck and not do wheel cylinders. Bad move. That bit me in the ass. A year later and a leaky cylinder was contaminating my right front causing exactly what you describe.

I also had a two-fold issue where the previous owner had put on a new master cylinder. Assuming they'd done it right, I never bothered to check but boy did the pedal feel light until right near the bottom and then it was brakes FULL ON.

Turned out, they didn't know enough to remove the brake rod retainer from the master cylinder. The car had power brakes, but either they got a manual brake master or all masters now come with that rod retainer. Regardless, you're supposed to remove that retainer if using on a power brake car.

Otherwise, if you don't, the rod in your power booster gets jammed into the back of the master and won't return to where it's supposed to.

So, it may not be a bad idea to double check that and while you have the master separated from the booster, if it's adjustable, be sure you don't have any pre-load on the master cylinder.

The master should be able to slip onto the booster without any force. If you have to push on it, or cinch it down with the bolts, the rod is too long.

Good luck!

Atlast I am in the shop. Looks like the adjuster is flipped. Would this be my issue as it is getting tighter as I stop? Im looking in the original mopar service manual and it is opposite.

can not be the adjuster, because when it is cold, it cant undo itself..it would be tight all the time..i would lift the front end up when hot and spin the wheels and see if the drums are binding like its out of round drums when the heat expands them

can not be the adjuster, because when it is cold, it cant undo itself..it would be tight all the time..i would lift the front end up when hot and spin the wheels and see if the drums are binding like its out of round drums when the heat expands them

AFAIK, a '69 RR with drums are not self adjusting.

How old are the brake flex hoses?
A hose can get a rupture in a way that will act like a check valve and not let the shoes retract fully.
Jack up the bad wheel, pump the brakes till the brake locks up, crack the bleed screw to see if it releases.

Wheel bearing was mentioned. Make sure the cotter pin is locking the castle nut adjustment. A right side unlocked castle nut will tighten bearing adjustment, a left side will loosen.

Not quite sure what you mean by flipped.
Carefully compare with the illustrations in your '69 Plymouth Shop manual noting which direction the foward arrow is.

The new (in '69) up brake hardware uses self adjusters that look like the ones on this page.
p7 1969 Drum Brake Service Highlights.

The adjustment thread is reverse of the earlier hardware.
See 1969 Servicing Highlights

I also discovered my new wheel cylinder is leaking. Since I am now going to bleed the system for the 4th time... what adapter do i need to eleminate the booster and use the 4 stud master cylinder or is it the same bolt pattern. Im goi g to eleiminate the rest of the things im questioning. Thr bearings are good and torqued. With cotter pin . Nothing is standing out.

for mc, see last page
http://www.imperialclub.org/Repair/Lit/Master/260/Page13.htm

filmstrip here has more pictures
http://www.imperialclub.org/Repair/Lit/Films/260/index.html

same MTSC booklets and filmstrips for '69 in different format also at
http://www.hamtramck-historical.com/MTSC/1969/ServiceConferenceMenu.shtml

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Without descriptions and/or pictures of what you have found, its hard to do more than point toward good resources for solving brake problems.
If the right front drum is hot, that would suggest dragging.

Are the brake lines new? And if so who did you buy them from? I wouldn't eliminate the booster until you find out what the real problem is.