'92 rear brakes too tight
 

I'm working on my mom's 1992 Camry.

It's rear brakes lock up easily, especially in gravel. The rears have been coming on too hard, and I believe this is causing the brake howling she's complaining about. (They get hot because they're doing the majority of the braking) I need to solve this issue quickly, as winter is coming & I don't have much confidence in my mom's driving ability and I know that it will be dangerous in snow if the rear brakes lock up so easily.

I've driven the car before and remember how the pedal used to feel before, .. and I can tell that now, it takes less foot pressure than before. I don't think the problem is caused by the front brakes not working properly. If that was the case, it would take more than normal amount of pedal pressure to stop the car. It currently takes LESS pedal pressure. They're actually kind of touchy.

I found no foreign objects when I took the drums off, just the normal black dust, and not an excessive amount. So I'm thinking either the self-adjusters malfunctioned & were too tight, (both of them at the same time?) or something's up with the proportioning valve. The wheels spun freely by hand when I jacked them up.

Since the right rear wheel rattles when you kick the tire, I'm also replacing the hub/bearing assembly.

The shoes are about 50% so I won't be changing those.

The hand brake is functioning correctly, ... at least it WAS before I backed off the self-adjusters.

Has anybody had this problem with the rear drum brakes coming on too hard? I have never heard of a proportioning valve failing on any vehicle.

I have no idea if the car has ABS brakes or not, BTW.

How much travel (number of clicks) in the hand brake before it becomes solid?

Inspect the parking brake cables and mechanism to make sure the shoes are completely releasing when the brake is off.

Do both rear brakes lock up? The cars braking system is divided up into two individual units each having a front and opposite side rear brake.

Do the front brakes work OK, no frozen caliper pistons?

How is the brake pedal operation when the engine is off (no brake booster operation)?

Any severe warping of the rear drums?

Wear shoes can cause grabbing. Since you are taking one side apart might replace the shoes, then clean and grease the metal contact points of the brake mechanism and shoes.

If the car has ABS there will be an icon on the dash that illuminates when the ign key is turned on showing the letters ABS or something like this. Each axle will have an electrical cable going to the ABS wheel sensor.

Before I screwed with it, the rears would lock up on pavement if I hit them much harder than I would for "normal" braking. The pedal was near the top of it's stroke when they'd start grabbing. But the wheels rotated freely when I was spinning them by hand, after putting the rear end of the car up on jackstands.

The hand brake would lock up the rear wheels on gravel only if I yanked it all the way up.

I replaced the hub/bearing assembly & brake drum on the right side, cleaned the black dust off the brake shoes on both sides, and loosened the self-adjusters about 1/3rd of a turn.

I took it out, and the first thing I noticed was it seems the rear wheels were still doing most of the braking because I had to hit the brake kind of hard to stop at the end of the gravel driveway. But then I realized that was probably just because the engine was cold and was idling fast, and fighting against the front brakes. I wasn't braking very hard, I was just going from 15 mph to zero over a distance of about 50 feet, just slowing down to check for traffic before pulling out on the road. After the engine warmed up, I didn't get that sensation of the rears working harder than the fronts again.

I ran it up to various speeds & hit the brakes to a full stop and it seemed to be working the same as they always have, before this rear brake issue happened. After a few quick stops, and after the engine was warmed up, I ran it up to 75 mph and stopped as quickly as I could without being stupid about it, and the car stopped a lot quicker than I expected. Then I repeated it from 80 mph & hit the brakes even harder than before, and it stopped quickly, much quicker than I expected, and there was no left-right pulling, and none of the wheels locked up, .. although I wasn't trying to make them lock up. I was actually just trying to get them hot so I could tell if they would squeak.

Since I backed off the self-adjusters, the parking brake barely works. It won't lock them up in gravel, but I'm not really concerned with the parking brake function because it's my mom's car & she never uses it. In fact I had to move a stupid little plastic "cup holder" thing in order to even get my hand around the parking brake handle.

I know the self adjusters, if working properly, will eventually tighten back up. Once they adjust themselves, if they're coming on harder than the fronts, I guess I'll be looking into the proportioning valve.

There's no way possible the car could have been braking that hard & fast if the front brakes were not functioning properly though. My guess is the car was stopping from 80 mph to zero in less than 200 feet.