2001 Silverado - Brakes Locking Up

Brakes Locking Up

Vehicle Specs:
2001 Silverado - V8 4.8L - Extended Cab - 103,000 miles

Well, not really locking up, but tend to keep a lot of pressure on them when I release the peddle.

I first noticed this occurence one day about 10 miles from my house. I was at a stop light and when the light turned green and I released my brake peddle, my truck did not move forward as fast as it normally does. Once I began to accelerate onto the freeway, I noticed that my steering wheel began to vibrate (as if my wheels were unbalanced). I also noticed that my automatic transmission was shifting into a lower gear to maintain a speed of 65mph. After 1/4 mile of this everything returned to normal. The rest of the trip (approximately 30 miles) was fine... no problems.

The next day (on my way to work) I had the same problem happen again. I was about 12 miles from home, when the steering wheel began to shake and the tranny had to shift to a lower gear to keep a speed of 65mph. This time I immediately got off at the next exit and had to stop at a red light before getting to a gas station. As soon as I stopped, I noticed smoke coming from my front left wheel. Not good !!!

I "carefully" touched the front right rim... VERY HOT. I jacked up and removed the front right wheel to assess the situation. I had to wear a pair of work gloves to touch the lugs nuts after removing them. This took about 5 minutes. After I got the wheel off, I spit on the rotor to see if it was still hot...hiss !!!

At this point I called a automotive tech friend of mine (neighbor) to see if he had any ideas. He said to go ahead and loosen the bleed valve to release the pressure in the caliper and to push the pads back to release their grip on the rotor. As soon as I did that, my truck (being on a slight slope) rolled back about 2 inches. Luckily, I had chucked the rear wheels. I found it odd that the rear wheels were locked also. I did not think to touch, or spit, on the other 3 rotors.

We immediately thought that my front calipers need to be replaced. I bought new calipers/pads and had the rotors turned. I then took my neighbors out to dinner (in my truck) in gratitude for his assistance with helping me replace my front brakes. The trip was about 20 miles. Brakes worked fine.

The next day (on my way to work), it happed again... at the same place. Shaking steering wheel and shifting tranny. I pulled over to see smoke coming from my left front wheel again. This time I felt all of the rims... VERY HOT !!! I removed the front left wheel, release the pressure and sat for 30 minutes to let them cool. I then eased home (applying very little pressure to my brakes). Once I got home, I felt the rims... not hot.

My neighbor pulled up some information on alldata.com and said the he had a sneaky suspicion that it might have something to do with the ABS. We disconnected the two connectors from the EBCM and he let me borrow his temperature gun. I made a test run. Everything seem to be working properly (except for the ABS light being on now, of course). I stopped around the same place I problems before, and tested the temps of the rotors:

Front Rotors: 135-150 degrees
Rear Rotors: 200-200 degrees

I then used the brakes (a bit more heavily) for about 5-6 miles and retested the temps:

Front: 195-200 degrees
Rear: 230-240 degrees

I made my way to work today with no issues. Once I got to work I retested the temps:

Front: 165-170 degrees
Rear (right): 250 degrees
Rear (left): 170 degrees

We decided to give it a couple of days and see what happens. If all goes well for a couple of days, I'm going to reconnect my ABS and test it again. If it fails, then I beleive we have found my problem.

I guess this FINALLY leads to a few questions for the masses.

1) Can the EBCM be faulty and NOT trigger the ABS lamp to come on?

2) If the problem DOES persist (with the ABS disconnected) what would be next thing to test?

Sorry for the long read, but I wanted to give as much info into my problem as possible.

Thanks,
Bryan

The same thing happened to me a couple years ago........ my mechanic immediately diagnosed the problem....... a worn out brake hose. Seems the rubber hose on my brake line had become a little soft. After I would apply the brakes then release, the hose was sucking itself shut and not releasing the pressure. It would take 10 to 15 minutes for the pressure to release.
Replaced the hose and I've had no problems since. Good luck!!

The same thing happened to me a couple years ago........ my mechanic immediately diagnosed the problem....... a worn out brake hose. Seems the rubber hose on my brake line had become a little soft. After I would apply the brakes then release, the hose was sucking itself shut and not releasing the pressure. It would take 10 to 15 minutes for the pressure to release.
Replaced the hose and I've had no problems since. Good luck!!

Was it one of the hoses that lead into just one of the calipers?

If it was, then (pardon my ignorance) would that cause "all" of the calipers to lock up?

Yes it was just one of the hoses leading to front passenger side. Just the one caliper was affected. I don't think that would cause all the calipers to remain locked. By the way..... after removing the old hose, I couldn't tell where the soft spot was. It all still felt pretty good to me and my mechanic said sometimes it's just a little section of the rubber that weakens.

i'd suspect the master is hanging up, possiblely contaminated fluid cause the seals to swell

i'd suspect the master is hanging up, possiblely contaminated fluid cause the seals to swell

I believe you might be right.

On my way home today, the brakes began to do the same thing (locking). Fortunately, I had the temperature gun and took a reading of the rotors:

Front: 385 Degrees
Rear: 185 Degrees

This was after traveling approximately 2 miles at about 25-30 mph.

We (actually my automotive tech neighbor) tested the brake fluid for contamination of copper with a litmus-type paper strip with a chemical. It showed to be ok. Unfortuantely, he won't back in town until Friday (It's Tuesday now). Is there any other way to test the reliability of my master cylinder?

I've only made one call to price out a new one at O'Reily's. They want $115 for a rebuilt ($20 Core). Is this about right?

if your going to keep the truck i would go with a new, i have always had crappy luck with rebuilds.
the only was to really test it is to put pressure gauges on the fittings of the master.
you can try jacking up the front and and try turning the tire while someone crack loose the fittings on the master, if the tire spins easyer its the master.
make sure you flush out the old fluid from the lines.

How can I tell if my master cylinder is equipped with a "hydra booster"?

When calling for pricing, they asked me this question.

How can I tell if my master cylinder is equipped with a "hydra booster"?

When calling for pricing, they asked me this question.

hydra booster uses the power steering to assist in breaking
look at the booster right behind the master if it has high pressure hoses going to it its hydra, if it just has a big vacuum line its a regular

Can you tell from this photo that I just took?

http://www.medicompinc.net/3rb/DSCN5738.jpg

its a regular vacum booster

could be an ABS pump goin bad...any grinding noises???pedal vibration???

could be an ABS pump goin bad...any grinding noises???pedal vibration???

Please don't take this offensively, but did you read my previous posts? My ABS light has never come on (except when I disconnected the cables that lead to it). If it was the ABS pump going out, then shouldn't I get the infamous "ABS light always on" problem, right?

I also posted, in a previous reply, that we disconnected the EBCM Module (ABS controller) altogether, and still have the same problem (locking up).

I believe I'm going to persue the idea that mjgjr72 mentioned. The master cylinder seems to be my culprit.

remove both front calapers and check the mounting bolts for rust. the calapers should float on the bolts. if thay get a ton of grit thay will drag and heat up. this will lead to the locking. also check the pistons ends to see if thay are rusty. same thing will happen.

do a vacume leak check on the brake buster. if it has a pin hole in it it will couse the front brakes to drag. took a long time to find one once. yes i know that one well. had a old ford that the front brake draged realy bad, then the back started draging. replaced every thing till we got to the buster. then it took 3 bad replacements to finly get a fresh rebuild. it was the first one a hole bunch of mechs ever seen.

remove both front calapers and check the mounting bolts for rust. the calapers should float on the bolts. if thay get a ton of grit thay will drag and heat up. this will lead to the locking.

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.

also check the pistons ends to see if thay are rusty. same thing will happen.

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

do a vacume leak check on the brake buster. if it has a pin hole in it it will couse the front brakes to drag. took a long time to find one once. yes i know that one well. had a old ford that the front brake draged realy bad, then the back started draging. replaced every thing till we got to the buster. then it took 3 bad replacements to finly get a fresh rebuild. it was the first one a hole bunch of mechs ever seen.

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

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

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.

Directional valve???????

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.

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.

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.

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

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

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.