2001 Silverado - Brakes Locking Up

[99redsilverado]

my abs pump was going bad, didnt throw a light.....i was just throwing out a suggestion, but yes your probly right it might be the master cylinder...dont have to jump on me like that

[gremlin96]

Originally Posted by Saltymut

I replaced the entire front brake assembly... mounting bolts, brackets, pads (everything) but still had the same problem with the brakes sticking. We pretty much ruled out that scenario.



Where are those located? If they are on the caliper, then nevermind, they got replaced also.



I've pretty much decided to put a new master cylinder in, but am still hoping for a more $financially$ sound idea. We'll give the look-over for leaks, but I don't ever recall seeing any drips in the driveway.

Thanks,
Bryan

no mater how hard you look you will not find a vacume leak driping on the floor.


fast way to check for a vacume leak is to get a ball valve and a section of hose. hook up the valve to the hose and connect the other end to the vacume line going into your brake buster. turn on the truck for a few seconds to get the vacume up. then close the valve. disconnct the side going to the trucks motor wate a min or two put finger over the open end of the valve and then open the valve if it trys to suck your finger into the end, then you dont have a leak.

or find some one with a vacume tester.

[rsad74]

Directional valve???????

[Saltymut]

Here's an update...

I ended up replacing the master cylinder, and totally purging (bleeding) all the old brake fluid (boy it was ugly looking). All seems to be working ok... for now. The true test will be my trip to work (35 Miles).

Thanks to everyone for their help and suggestions.

[gremlin96]

hope the problem is fixed.

i had to call chevy and complain. my truck is still under wornty and still not fixed right. every time i take it in thay say no codes cant find the problem. or no codes yes you have a big problem but we cant find it.

come back in six months and we will try to see if there is a up date for your computer.

i still blow thru stop signs, abs kicking in at low speeds. you just got to love not stoping in stop and go trafic, and parking lots.

so far the only fix is to ride the motor cycle in the rain and the truck in dry weather. chevy is no help.

[BlenderWizard]

Originally Posted by Saltymut

Where are those located? If they are on the caliper, then nevermind, they got replaced also.

Yeah, they're on the caliper; it's the round center part that engages the pad to the rotor.

[mjgjr72]

Originally Posted by Saltymut

Here's an update...

I ended up replacing the master cylinder, and totally purging (bleeding) all the old brake fluid (boy it was ugly looking). All seems to be working ok... for now. The true test will be my trip to work (35 Miles).

Thanks to everyone for their help and suggestions.

fingers are crossed

[mjgjr72]

Originally Posted by gremlin96

hope the problem is fixed.

i had to call chevy and complain. my truck is still under wornty and still not fixed right. every time i take it in thay say no codes cant find the problem. or no codes yes you have a big problem but we cant find it.

come back in six months and we will try to see if there is a up date for your computer.

i still blow thru stop signs, abs kicking in at low speeds. you just got to love not stoping in stop and go trafic, and parking lots.

so far the only fix is to ride the motor cycle in the rain and the truck in dry weather. chevy is no help.

from another thread hope it helps, also you can always try another dealer

Originally Posted by GMMerlin

Sorry I havent been cruising the boards here lately, but from the looks of it, you are on the right path.
Here is a copy of a GM bulletin that applies to you concerns of low speed ABS activation.
Someone else mentioned the problem of the ABS pump running all the time...that is a separate issue caused by an internal failure of the ABS module....there are NO RECALLS on these issues at this time.
On the subject of the ABS pump run on, there is a gentleman on these boards..I believe his name is Ken Spragg of circuit solutions that had a fix for this...If someone can get in touch with him and have him contact me, it would be greatly appriciated.



here is the bulletin

Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface) #03-05-25-007 - (09/29/2003)
Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface)
2002-2004 Cadillac Escalade, Escalade EXT

2003-2004 Cadillac Escalade ESV

1999-2004 Chevrolet Silverado

2001-2004 Chevrolet Suburban, Tahoe

2002-2004 Chevrolet Avalanche

2003-2004 Chevrolet Express

1999-2004 GMC Sierra

2001-2004 GMC Yukon, Yukon XL

2003-2004 GMC Savana

2003-2004 HUMMER H2

Condition
Some customers may comment on ABS activation at low speeds, usually below 8 km/h (5 mph). Upon investigation, the technician will find no DTCs set.

Cause
The cause of this condition may be an increased air gap between the wheel speed sensor and the hub reluctor ring due to rust and debris built up on the sensor mounting surface.

Correction
Measure AC voltage and clean the wheel speed sensor mounting surfaces.

Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in the General Information sub-section of the Service Manual (SI Document ID #899664).
Disconnect both the front wheel speed sensor (WSS) connectors at the frame and harness.
Place a Digital Volt Meter (DVM) across the terminals of each WSS connector.
Rotate the wheel clockwise approximately one revolution per second. The minimum reading should be at least 350 ACmV's. If the reading is less than 350 ACmV's, remove the wheel speed sensor. Refer to the applicable Wheel Speed Sensor Replacement procedure in the ABS sub-section of the Service Manual. Plug the WSS bore in order to prevent debris from falling into the hub during service.
Clean the WSS mounting surface on the hub to remove any rust or corrosion using a wire brush, or equivalent.

Important
Make sure that the sensor sits flat on the hub. Check the sensor flange against a straight edge to ensure flatness. If the sensor flange is distorted, replace the sensor.


Apply a thin layer of bearing grease to the hub surface and sensor O-ring prior to sensor installation. Use ONLY Wheel Bearing Lubricant, P/N 01051344 (Canadian P/N 993037).
Install either the original sensor or a new one in the hub. Ensure that the sensor is seated flush against the hub. Refer to the applicable Wheel Speed Sensor Replacement procedure in the ABS sub-section of the Service Manual.
Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel. The voltage should now read at least 350 ACmV's.