98 Chevy Truck Brake Troubleshooting

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wolfehunter

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Feb 18, 2009
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I don't drive it much as it sometimes will sit a week but recently started having a brake issue. Due to cold weather? Caliper hanging up? Braking at higher speeds I don't notice an issue but stop and go or at stop signs the brake pedal pulses sometimes and the truck continues to coast. Scared the [censored] out of me as I almost drifted through a stop sign! Almost feels as though the ABS is kicking in. Checked fluid level and it is good. I do know my rotors could be replaced due to slight warping but not terrible. Pads replaced 7 months ago and are good. This morning on way to work I did jump on them a little harder at stop signs and worked fine except right before the truck was about to stop I could feel the brakes slip or let up. Brake pedal feels normal.....not spongy except when the ABS or slipping kicks in. Of course then they get mushy but it doesn't stop well. Any way I can self diagnose and repair?

Thanks,
Scott
 
First, determine whether it occurs at once per tire revolution or whether it is the ABS. The ABS won't feel like a "pulse", more like a chatter.

Assuming it is not the ABS, I would question the condition of your rotors. Heavy contaminant (in this case, likely rust) buildup can cause the pulsation you're describing.
 
Probably is the ABS. They had issues with the wheel speed sensors getting junk on them. They're in the wheel bearing assy (assuming it's 4wd) Pull them out and I bet you'll find them covered.
 
Ok, thanks for the suggestions. It is a 4WD so I think I will check the wheel speed sensors and replace the rotors while I'm at it. I will inspect the pads closer but is it imperative to replace the pads since only 7 months old?
 
If it's ABS it "should" disable when you apply the e-brake one click. I would yank the fuse, though, and drive around for a day to see if it improves.

But if you panic/forget, try hitting the e-brake a little.
 
Thanks for the "head's up". I will give that a try. I did panic the first time it happened. Been abiding by the "2 second rule + some" when following vehicles! Hope the brakes don't fail in an emergency situation. E-brake only locks up one rear wheel....correct?
 
My 96 had the master cylinder go, but the symptom was both front brakes were stuck, but it's definitely something to look for with your truck. Also take off the rear wheels and drums and peel back the rubber boot on the wheel cylinders and check if there is oil in them. If so replace them, it may not be leaking externally but it can definitely cause brake mushiness and issues. I just fixed an Xterra with that issue.
 
Originally Posted By: wolfehunter
E-brake only locks up one rear wheel....correct?


Believe the e-brake light is wired into the ABS system to disable it. Try it before you trust it.

On my buick century, locking the rear wheels via e-brake de facto disabled ABS for the rest of the key cycle. It thought I had dud sensors/ actuators back there. The light was on, and ABS was off.
 
Is this the vintage where rust would build under the sensor and lift it away? I recall that was a problem for somewhere in this time frame -- but I'd think that disable ABS altogether, not cause it to kick on.

E-brake works on both rear drums. May lock up one if the cables are not adjusted right, or something is frozen, or dumb luck (could be worse, might lock both up).
 
So I finally got to work on cleaning up my hub and ABS sensors yesterday. I couldn't get the 15 year old sensors out of the hub without snapping them off. I took the bolt out that holds them in place and pulled/twisted, used a pliers and screwdriver and eventually snapped them both off!! I was able to use a needle nose pliers to pull the broken part of the sensors out. I can see the hub spin so I think I got everything out. I ordered some AC Delco replacement sensors from RockAuto for $28 a piece. Cleaned up the corrosion on the hub and hit it with rustoleum so I'm ready to go when sensors and new rotors arrive.
 
Just wanted to thank those who gave me some good advice! New sensors seemed to solve my "creeping brakes" problem. Happy New Year all.
 
So here it is a little over 2 years later and problem is back. I removed the sensors on each hub and cleaned up any corrosion on the area the sensor sits on which wasn't too bad. Reinstalled and still had the creeping problem and ABS coming on while braking un der 10 mph.

So I tested each of the sensors with a meter while having my kids spin the wheels. Passenger side I got over 400 ACmV's but driver's side would only read 210 ACmV's. Checked a few times and definitely a lower reading on that side spinning wheels as equally as we could. So I got a new AC Delco wheel speed sensor and put it on the driver's side tonight. No dice! I know I need to pull the wheel again and check with meter.

My question is if I get the lower reading again with the meter is it possible something is wrong inside the hub? I understand the sensor reads rings or a magnet of some sort inside the hub. Could that be the issue? Or how do I rule out the ABS Module or Brain itself? I have heard that is an expensive fix! Any help diagnosing is appreciated.
 
Did you remove some rusty marterial from under the sensor? Maybe the sensor is sitting on the rust and too far away. Should be sitting on bare metal. Maybe the replacement is bad too? I've had new in box parts be bad.... don't be surprised if the Delco is, they're made in China now.
 
Yes, I removed all the corrosion (wasn't much accumulated since done December of 2013) and made sure all debris was gone as to not hold the sensor off. One thing I did notice when spinning the wheels by hand was the driver's side wheel definitely has more resistance/drag to it. I am thinking of replacing both wheel hub bearing assemblies since they are original and have 130K on them.

Going to swap sensors to opposite sides and see what readings I get per George's suggestion too. I kept the 2 year old sensor I replaced with the AC Delco just in case they are good.

Lots of wheel hub bearing assemblies to choose from with price range from $51 to $250 including Pronto, Centric, Moog, WJB, Dorman, Timken, Callahan etc..... Truck is not a daily driver so thinking I don't need to spend a fortune but don't want to buy junk either! Any suggestions?
 
I would just like to add that at work I will never replace a sensor inside a sealed hub. It gets the whole hub unit replaced with sensor pretty installed.
 
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