concerning my 1998:

I thought this was only a problem on damp mornings at the very first application of the brakes, but now I think something is wrong.

The rear brakes will lock up at low speeds if I am not real careful about pressing in the brake pedal. I was told that the rear axle seals may be leaking, so I pulled the drums and checked. Everything looked nice and dusty. There was only a little wetness around back of the axle hub. (not to be confused with the brake drum). But it didnt seem like enough wetness to be concerned with. THe pads were totally dry. Since I had the truck jacked up, I spun the wheels, and could hear the brakes dragging ever so slightly. This was with the truck in nuetral, and the parking brake off. So, from what I have been told, this is kosher. Also, the master cylinder is dirty. It looks like "oil soaked dirt". I guess I should taste it, and see what kind of fluid attracted the dirt.........lol...jk

I think that there is something wrong with the ABS system. Could it be that this truck needs a brake system flush? Its got 115k miles onthe original fluid, and the resivoir has plenty in it.

This is not a terrible problem, it just affects me when Im not payng attention, and give a little too much pressure when easing out of my driveway......gives a little whiplash.


any ideas?
Thanks,
Phillip

 

1. Any brake fluid with 115K miles needs flushing. But this is most likely not your problem.

2. Do your rear brakes lock up only when backing or also when moving forward? When moving forward, do you have enough brake power to activate your ABS?

 

My wife's rig is like that. At times it is a touchy, lockin up, SOB. When she first told me about it, then she had just ran through some water, something like that you know. I drove it a while sometime after that. I locked them up going maybe 10mph when I first got it in. Very touchy compared to mine, so I figured it was just me used to a harder pedal. Anyhow hers is touchy like that. I would be very interested in others' dealings with this problem? I pulled her drums to look at her shoes and they were fine, just like yours. No seals leaking, fluid level fine, etc.

 

The dark color of your brake fluid is caused from moisture in your system and causing the internals to rust and deteriorate. Definitely flush it until fresh fluid comes out all bleeders. The abs may be sticky from the contaminated fluid so after the flush go for a ride and work the brakes hard and make the abs work several times. Wait for the brakes to cool down and go for a normal run to check the brake operation.
Also the dark contaminated fluid has a lower boiling point and will boil in the calipers and produce air which will make the brake pedal spongy and the abs malfunction.
Another cause for grabby brakes is the material will either glaze or absorb moisture. If the fronts glaze the rears have to work harder before the fronts work. Moisture will cause a grabby brake. Some linings are too soft and grab too much compared to the other axle.
The best proceedure to follow is do 4-6 heavy brake applications from arround 50 (don't smoke them) and after cooldown check if the problem goes away. If it keeps comming back, just replace the linings.

 

Did you mean wheel cylinder here by chance? A leaky wheel cylinder will cause the rear brakes to do lockup on a whim just like a leaky axle may. If you haven't upgraded to the Cheby cylinders, consider this your invitation. Napa #4637337 - GM 1 ton wheel cylinders

 

Any "wetness" around the wheel cylinder is bad. Could be the cause of all of the problems, but like I said, regardless, the leaky cylinders should be replaced, fluid flushed (DON'T PUMP THE PEDAL ALL THE WAY TO THE FLOOR WHEN BLEEDING BRAKES). And all brake componets and drums/rotors cleaned.

The gm wheel cylinders are the way to go. Time for a little work Kevin

 

No, the wheel cylinders look fine. I was talking about the brake master cylinder under the hood.

Is flushing the brake system something I can do at home? or should I take to someplace like "brakecheck"?

I am beginning to think that HemiCat is right. The rear brakes are probly glazed over, and the fluid needs flushing. The rear brake pads looked good, but that doesnt mean anything. Im gonna do a flush, and change the linings.

THanks!!
Phillip

 

I adjusted mine up and that seemed to help alot. Mine were only touchy in AM for the first couple of soft stops. This reminds me that I need to flush my brake fluid also. Yet another thing on the list.

 

Changing the fluid isn't a very big deal, just don't let the brake pedal go all the way to the floor. Or if you're lazy like me, I just use a mityvac on the bleeder screw.

 

mine just started to lock up too
i thought it was the auto-adjuster
i have to keep adjusting it so it'll stop locking up
im going to change mine out

 

Mine lock up as well. I have the big mud tires you see in my photo gallery, so was wondering if that had anything to do with it. I have not tried hammering the brakes to see if the ABS does indeed work. Don't know when the last time the lines were flushed, either as I've only had the truck a short while. Probably worth flushing the lines and seeing if that does anything...
Dave

 

My truck did that from new, first touch was grabby at the back then ok after I thought it had something to do with the vacume or lack of (I seldom idle longer than 15-20 secs before throwing it in gear and idleing away) Anyway the Chebby wheel cyl trick seemed to make it go away? Go figure but I'm not goona complain cause I dont want it back

 

So you only changed the cylinder, not the linings too?

 

Yep, stock linings are still in

 

When you flush your brake fluid, use a suction gun or a turkey baster to empty your master cyl reservoir and make sure the bottom is clean. Refill the res with fresh fluid and start bleeding the brakes until the fluid comes out clean.
Good luck