Rear brakes dragging and locking up at low speeds

[Bessie]

1992 bronco, 5.0, auto. 150k.

Been having this issue for a while now and can't figure it out. When driving regularly and come to a stop sign and start to accelerate again it feels like the rear brakes are binding up. They also lock up prematurely at times. Yesterday I pulled the drums expecting to see worn shoes and broken springs but the brakes looked perfect and everything looked fairly new. There was no oil or brake fluid leaking from anywhere. Could this be a rear wheel bearing going bad? There are no other noises except a medium pitch squeak at less than 1 mph which happens sometimes.

What are the symptoms of a bad rear wheel bearing?

How do I check if they are bad?

Can this be a brake issue?

What should I check?

 

[miesk5]

Leaky isolation valve.

yo B,

You have the Rear Anti-lock Brake System (RABS) and have a Red Brake Warning Light & a Yellow Rear ABS Warning Light

are either or both on while driving?

both the red BRAKE and yellow REAR ABS instrument panel warning lights to alert the driver to a system malfunction. Both lights must be working properly to assist in concern diagnosis. The steps listed below must be followed prior to beginning the diagnostic procedure.

WARNING: PLACE BLOCKS BEHIND THE REAR WHEELS (1007) AND IN FRONT OF THE FRONT WHEELS TO PREVENT THE VEHICLE FROM MOVING WHILE THE SYSTEM PRE-CHECK IS BEING DONE.

For 4-wheel drive vehicles, shift into 2-wheel drive. Drive the vehicle to a level area, and place the shift lever in PARK for automatic transmissions (7003) and NEUTRAL for manual transmissions. Turn the ignition off, set the parking brake and turn on the running lamps. Place blocks behind the wheels.

Release the parking brake and continue to the System Pre-Check.

Brake Light Self Check

The red BRAKE warning light is used to indicate a low fluid level condition or parking brake applied condition. To check this light,

RABS Self Test & Diagnosis Codes; "...The possible flashout codes are listed and explained in the Flash Codes Chart. Note that Codes 1 and 16 are not used. Flashout Codes Whenever the yellow REAR ABS light comes on during normal operation, a flashout code may be obtained to aid in problem diagnosis. If the vehicle is shut off before the code is read from a RABS-I module, the code will be lost. In some cases, the code may reappear when the vehicle is restarted. In other cases, the vehicle may have to be driven to reproduce the problem and, if the problem was associated with an intermittent condition, it may be difficult to reproduce. Therefore, whenever possible, it is recommended that the code be read before the vehicle is shut off. RABS II modules have been designed with Keep Alive Memory to preserve stored codes during key-off, and are to be used to service all prior year RABS I systems, except for 1987 and 1988 Bronco II vehicles. WARNING: PLACE BLOCKS BEHIND THE REAR WHEELS AND IN FRONT OF THE FRONT WHEELS TO PREVENT THE VEHICLE FROM MOVING WHILE THE FLASHOUT CODE IS BEING TAKEN. NOTE: If the red BRAKE light is also on, due to a grounding of the fluid level circuit (perhaps low brake fluid), no flashout code will be flashed and the REAR ABS light will remain on steadily. NOTE: If there is more than one system fault only the first recognized flashout code may be obtained. Obtaining the Flashout Code A flashout code may be obtained only when the yellow REAR ABS light is on. No code will be flashed if the system is OK. There are certain faults (those associated with the fluid level switch or loss of power to the module) that will cause the system to be deactivated and the REAR ABS light to be illuminated, but will not provide a diagnostic flashout code. Before obtaining the flashout code, drive the vehicle to a level area, and place the shift lever in PARK for automatic transmissions and NEUTRAL for manual transmissions. Notice whether the red BRAKE light is on or not (for future reference) and then apply the parking brake. If a RABS(-1) module is installed, keep the ignition key in the ON position so that the code will not be lost. RABS II modules have been designed with Keep Alive Memory to preserve stored codes during key-off, and are to be used to service all prior year RABS I systems, except for 1987 and 1988 Bronco II vehicles. WARNING: PLACE BLOCKS BEHIND THE REAR WHEELS AND IN FRONT OF THE FRONT WHEELS TO PREVENT THE VEHICLE FROM MOVING WHILE THE FLASHOUT CODE IS BEING TAKEN. To obtain the flashout code, locate the RABS diagnostic connector (with the Bk/Or wire), and attach a jumper wire to it. Momentarily ground it to the chassis. When the ground is made and then broken, the REAR ABS light should begin to flash. NOTE: If the red BRAKE light was on (as noticed before the parking brake was applied), the problem may be with the low fluid level circuit and, in this case, no flashout code will be flashed and the light will remain on steadily. The code consists of a number of short flashes and ends with a long flash. Count the short flashes and include the following long flash in the count to obtain the code number. For example, three short flashes followed by one long flash indicates Flashout Code Four. The code will continue to repeat itself until the key is turned off. It is recommended that the code be verified by reading it several times. In addition, the first code flashed may be too short because it may have been started in the middle. It should be ignored..."
Source: by Steve

 On-Board Diagnostics

Diagnostic Trouble Codes, Retrieving

RABS Self Test; except 93-96; "...The 90 service manual gives a routine to pull RABS codes. When the light comes on, don't turn the truck off before reading the codes. Put it in park, chock both front & rear of the wheels, note whether the red brake light is lit also, then momentarily ground the test connector. The test connector comes out of a large loom under the dash, coming through the firewall, near the parking brake. On mine there are 2 similar connectors in that area, the correct one has only 1 black wire with an orange tracer running to it, & was hidden on top of the loom. The correct one is hanging down on the bottom right of the pic below. After you've grounded & ungrounded the wire, the yellow abs light starts to flash. Count the flashes. It said to not count the 1st series, because it may start in the middle. The last flash of the series is a long flash. Then it repeats over & over, until you turn the key off. Count all of the short flashes & the long one together (So 4 short & 1 long is code #5). If I remember right, it should be a number between 2 & 15 or so. If you follow Steve83's sig link, & then go to his Brakes & Hubs album, he has the code definitions for RABS.." READ MUCH MORE

Source: by ElKabong (Ken, El Kabong)

One or Both Rear Wheels Lock Up:

Brake related concern:

Damp or contaminated rear brake shoe linings.Stuck/leaking rear wheel cylinder.Rear brake adjusted too tight

Hung-up parking brake

Hubs engaged although shift lever is in 4x2 position

Faulty 4x4 indicator switch or short to 12v in 4x4

Stoplamp input to anti-lock electronic control module not present

 Stoplamps inoperative 

or

RABS sensor/sensor ring assembly does not produce sufficient output

Damaged RABS valve reset switch