I have just noticed lately that my brakes release slowly after I apply them. It is almost as if the power brakes are pulling the pedal down. The problem seems to happen more when I apply the brakes at highway speeds. Once the car slows down enough or I start to accelerate again, the pedal returns to its normal height.

Some background information:
* new calipers on both sides
* brakes recently bled but pedal doesn't seem as firm as I would expect it should be
* checked both rear brakes last night and all hardware seems to be in good working order
* mechanic informed me that my drums are getting thin from rusting away on the outside. Although the insides are still within spec, he noticed the drum was flexing when the brakes were applied
* right rear brake sometimes locks up when braking hard on dry pavement

Any suggestions?

Frank: Power brakes or unboosted?

Dan,
I wondered that too, until I re-read his post.
Frank,
Surely this can't be good Jerry

_________________
There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.

...you checked the back brakes, so you're sure the shooz are not contaminated, right?

D/W

_________________

If it ain't broke, fix it!

When I checked the back brakes, I did not see any contamination on the shoes. The friction material on both sides has a normal appearance and there is no leakage from the wheel cylinders.

As this car is regularly driven in the winter, there is rust on the drums and everywhere else. I have my doubts about the mechanics comment about thin drums. I have seen drums that are being applied move around slightly due to the expanding shoes because the wheels aren't holding them tightly in place. I was, however, thinking about replacing the drums later on when the shoes wear out.

Power brakes + slow release = suspect booster.

I was thinking it might be booster-related but it is fairly new. I had a problem with it a few years ago and replaced it. I am really disappointed in the replacement parts industry as parts nowadays seem to only last a little longer than the warranty. I will have to take it apart sometime and see for myself what could be the problem.

Does anyone have a idea of what in the booster could cause this?

On my aspen, it was simply that the brake pedal needed some oil...

Yeah, "remanufactured" parts from the parts store are a real no-no. They're worse than worthless, regardless of how fancy the warranty is ("Lifetime Warranty!" means you get to spend your "lifetime" replacing cräppy parts under "warranty". Patronize the remaining craftsmen! Booster Dewey has been rebuilding brake boosters for years, and his rates are very reasonable.
Usually in the valving—if the booster's forward section doesn't vent immediatly upon release of the brake pedal, you'll get slow return.

Having said that: Why run a booster at all? Unboosted disc brakes work great on A-bodies, and are much easier to modulate, especially in slippery conditions.

I'm sure this question has been answered before but it takes me forever to search the forum with my dialup connection. Is converting to unboosted brakes simply a matter of removing the booster from my brake setup?

Conceptually, pretty much. You have to take care with the hardlines that run from the master down to the metering block, 'cause they're a little longer with the boosted setup. You can add another half-coil to the coiled section and this is usually enough to take up the extra length. You'll need a nonpower-brake master cylinder pushrod and the rubber bushing that holds it into the recess in the rear face of the rear piston. Also, some years use different-bore master cylinders for power vs. nonpower.

The fluid could be leaking slowly past the seals in the master cylinder when you press the brake. My ''74 Dart and my '73 B100 had this same problem until I replaced the master cylinder.

With the arrival of warmer weather, my brakes do not seem to be slow to release anymore and seem to be working just fine now.

Coincidentally, while I was trying to check things out, I slightly rotated the vacuum check valve on the booster. This is the small black plastic part that the vacuum hose from the engine is connected to. It seemed to me that the brakes released slightly faster afterwards. After having another look at this valve, there is nothing obvious in it that would indicate a change in position would have any effect on the rate of release.

jl737: My master cylinder is also new and there is nothing to indicate that there is any leakage in the seals. I earlier replaced the master cylinder because the pedal would slowly sink to floor while I was holding my foot on it.

Almost as though the rubber disc in the check valve is getting old and gets harder than it should in cold weather. Throw in a new check valve.