Brake Problems

STOP. CHANGING. PARTS. UNTIL. YOU. DISCOVER. THE. REAL. PROBLEM!

All four corners? I haven’t checked, drums or disc in back? What is vacuum reading?

Brake chatter is sometimes an indication of overload... is the truck empty most of the time?

Yes truck is always empty

It all needed changing anyways but what do you mean by what is the vacuum reading?

The vacuum booster - the big roundish deal mounted with the master cyl and the reservoir. This needs vacuum to operate. This vacuum line can crack or work loose.

Are you working with a Haynes Manual, Chiltons... something like that?

I read the OP again, read lyn’s comments, and now I wonder...

Are you, dcox88, certain this is a brake problem? As stated, bearings maybe, seems it could well be transmission problem.

Brake troubles are pretty serious - if you can’t reliably slow and stop the truck, ya better park it.

It has drums in the rear.

After 28 years on the road, it could be some quirk that is rare.

There is this

the brake proportioning valve.

Symptoms of a Bad or Failing Proportioning/Combination Valve ...

Differential fluid so old it’s congealed, we don’t know if we have 4WD and what hasn’t been maintained there, different size tires...

Might be a cat jammed in the belt/pulley system.

And we have no idea the colors of the vehicle, or if it has a set of those rubber calf nuts hanging from the hitch receiver.

I do have 275/60/15 tires on there and they are wide and the wheels on them are pretty rough so could that possibly be the problem? I still have my stocks so I could put those back on and see if that' helps

It's not the transmission bc after I get done driving you can even touch the wheels without the burning your hand. That's how bad it is.

Is the truck 4WD?

Did you replace the rotors? New ones? How about the rear drums? New ones?

Please confirm the brake oil used, and confirm proper air bleed procedure has been performed, and the reservoir is at capacity.

You said new ‘brakes’. I presume this means front pads and rear shoes. Is this a misguided presumption?

You aren’t really giving us a lot to go on.

It's 2WD. I've changed everything on the front and bled everything when I did it. I have not changed anything on the back brakes. Would having bad back brakes make my front wheels heat up like that?

No.

It sounds like your pads are getting wedged in the caliper, so they don't slide back smoothly when hydraulic pressure is released, assuming the master cylinder bleed port for the front brakes is clear when your pedal is released (same as leaving your foot lightly on the brake). Make sure your brake pedal comes back normally, light touch as well as heavy. You can have someone pump the brakes while looking in the top of the master cylinder, when the pedal is released, you should see a small surge (like little fountain) from each compartment, that is the vent hole releasing the caliper pressure. The volume that returns from the pressure lines is the rubber sections of brake hoses returning to their un-pressurized inside diameter.

The fit tolerance between the metal caliper slots and the pads is important, so if sloppy after-market parts tolerances stacked up in the wrong direction, the pads can wedge up and not release.

If the caliper mounts are not reasonably square with the rotor surface, you could also wedge the pads. This would appear to be impossible without serious damage, and you'd expect the brakes to pull to one side or the other, especially on front and under hard braking. In order for front wheel bearing play to cause this, the wheel, when jacked up, should appear to be ready to fall off.

Again, if unusual circumstances, the truck should pull noticeably to one side or the other when you put on the brakes at 30-40mph, maybe hands off the wheel?

If it stops fairly evenly, then I'd suspect uniform parts tolerance, such as wrong parts from supplier, close but incorrect.

Tough one...

I don't normally challenge anyone about car problems, but your post is full of misinformation, conjecture and speculation.

Pads don't, don't slide much at all, smoothly or otherwise. The pads hardly move at all except to contact the disk when you push the brake pedal. The pads are always just clear of the disk, they do not "retract" by spring pressure like drum brake shoes do. As the pads wear, fluid is displaced from the master cylinder in to the brake lines and behind the caliper piston so that is why as your pads wear, the fluid level drops in the master cylinder.

This statement, "The volume that returns from the pressure lines is the rubber sections of brake hoses returning to their un-pressurized inside diameter" is complete nonsense!

Not sure what you are trying to say here, "fit tolerance between the metal caliper slots and the pads is important."

That's enough, but I couldn't just let it go.

If the pads are small enough to wedge in the caliper ways, they will stick. You can experience this during disassembly, I'm surprised you haven't.

The pads slide in the caliper according to the wheel bearing clearance.

The rest of your information is correct....

"The pads slide in the caliper according to the wheel bearing clearance."

Wheel bearing clearance plays only a small part in this, unless, as someone said (maybe you) the wheel is about to fall off.

Actually the caliper moves out on hardened pins bolted to the backing plate as the pads wear. If the caliper sticks on one pin you will experience very uneven wear.

Not meaning to pick nits, but..................

Wheel bearing clearance is not insignificant when you look at pad to rotor running clearances. Not to say that could be solely responsible for pad backing plate wedging in the caliper, but a combination of unfortunate stacked tolerances and some pad to caliper temperature differential could add up to trouble. My bet for this seems to have been self-diagnosed by the OP, noting there is no free-play in the pedal.

We’re not certain the rotors were removed at all, let alone machined or replaced.

OP has been asked twice about them and won’t confirm.

And now I guess the pedal is hard... not sure just what to do with that pearl of information.

Fact is, we don't know.

Speculation all around.

I'll bet $20.00 on the gray.

Sounds like you have a bad brake line, and you might have a bad tire on the front, or alignment problem....change the brakes lines and look for uneven wear on the front tires...

We still don’t know if he has a heavy-half or a one-ton, blue or red.

Maybe rust red?

You might be thinking of the ‘Chick Magnet’.

She was something; Rust Bloom Red and Primer Grey, just a hint of chrome peeking out of those rusted spokey wheels. Grimy blue-tinted windows and torn bug screens, barely a shadow of the once glamorous conversion van.

Took her to the recycle yard, got $140 bucks a ton. Brakes were workin.

I would try lubricating the slider pins first before replacing any parts.

Has the truck been lifted, possibly throwing the suspension geometry out of whack? Has the front end been aligned properly?

Yeah I took it when it first started shaking to get aligned and that didn't help

Lets look at diagnostics.

Engine off. Truck with front wheels more or less straight, back wheels blocked, raise the front end.

Give each wheel a spin. Are they both quite free? This tell you if there is a misadjusted or misinstalled part.

Report back with results, we can go from there.

They hardly spin at all.

Okay.

Some part is incorrect for the application, or some part is installed incorrectly.

At this time, only a few parts are in play. Now, we need to be certain: NEW rotors are installed, NEW bearings, NEW calipers, and NEW pads.

If all that is yes, did you POLISH the spindles, and did you grease the ever-lovin daylights out of the bearings with appropriate grease? What color was the grease?

The castle nut might be too tight. I liked to torque mine in to seat the bearings and then loosen it back a notch, drive around the block, and then re-adjust. Makes for a smooth and well aligned wheel bearing. I like to remove the caliper when doing this (put back to drive DUH), so the rotor/hub can spin free when the castle nut tension is just right.

What you describe is easily explained if you have seriously deformed (out of round) drums. The auto backlash tigtening mechanism detects baclash on drum valey and operates, and since it only moves one-way, once it moves (tightens), won't loosen up. Then heat produced from intermitent contact makes things worse and worse. It will only partially loosen up when brakes cool down and the cycle repeats. S.M.

Drum brake adjusters only advance the star wheel when stopping in reverse.

But the heat is coming from the front wheels and I only have drums on the back brakes

Disk brake pads, even when working perfectly, always drag on the rotor. Most do not have any return springs like drum brakes do.

Hot wheels in normal for disk brakes.

Yeah sure but it's not just a little warm they're so hot you can't touch them.

Sounds like classic stuck calipers. Now why your calipers stick could be just from them wearing out. Carefully look for any grooves in pistons and slide ponts. Lubricate only with grease rated for the temperatures. I would first replace the flexible hoses as SolarEagle suggested. They are so often overlooked, inexpensive and this is exactly their failure mode.

I owned a 1988 Silverado 3500, white, regular cab, long bed, 4WD, automatic trans., 350 cubic inch engine. Disc brakes in the front, Drum in the rear.

The "anti-lock" system was terrible, it was more like "always-lock".

More than once after hard breaking, the rear drums would stay locked fof a second (seemed like longer) after I released the brake pedal and the truck would start to swerve, luckily I was able to regain control.

I disconnected the "ABS" system and it was much safer.

I've disconnected the abs and it still does it.

I wonder if anything has been measured instead of just doing the simple but expensive "shotgun" replace everything you can think of approach.

Then again this is a twenty eight year old vehicle. If one averages a paltry 10,000 miles every year then this will be 280,000 miles on this truck. The entire steering and drivetrain geometry could easily be off just enough to prevent shoes or pads from properly releasing every time. That's another point, we know that this is a recurring problem but we don't know how often this happens.

Lastly, cheap rebuilt calipers are notorious for failing again. A properly diagnosed sticking caliper may be replaced by a rebuilt sticking caliper.

After reading most of the comments you should check the two flex hoses at the front wheels and the one at rear axle. In my mechanical life numerous times I found these hoses swelled up so that you could apply the brakes but they will not release and or hard to apply brakes followed by failure to release. Quite common for sure.

I have experienced the same brake dragging issue with the root cause being the flex hose(s). Make sure all components are free to move as well... pins lubricated, etc.

I've already changed the two flex hoses but I have not changed the one in the back because I didn't think that would affect the front would it?

It sounds like an air in the system problem, when you brake the air in the fluid expands and applies the brakes harder, I assume this gets worse the more you travel, give the system a good clean out, (I would do it a couple of times) then make sure you bleed the system thoroughly, another cause could be a faulty valve on the brake master cylinder vacuum chamber which could apply the brakes, you can test this by clamping the vacuum tube, or pull it out and stopper it then dive around to see if the same thing happens, I can't stress the importance of finding somewhere safe to try this as your brake efficiency will be a lot less without the vacuum.

Bazzer

I've read that the vacuum booster (brake booster) causes a hard pedal and mine is very hard almost to the point where I don't even have to press it.

..."Just like with the master cylinder not releasing causing the brake drag, a caliper not releasing and staying applied can do the same thing. ... If the caliper is not properly aligned with the rotor, a drag can occur. This is usually caused by a bent caliper mounting bracket or severely warped rotors and pads."...

https://techtalk.mpbrakes.com/how-to-series/how-to-diagnosing-and-fixing-brake-drag

Which points to a fault with the vacuum side, It's applying the brakes through a faulty valve to the booster. When you lose vacuum the pedal gets hard, If you put your foot on the brakes of a vehicle that doesn't have a problem, start the engine and your foot will go down, if you then turn off the engine the pedal goes hard again.

Bazzer

Like the master cylinder is not releasing the pressure in the lines because the booster has no free-play in the pedal linkage. There is an adjustment for this. Or the vacuum valve is leaking slightly, equivalent to you riding the brake pedal, which heats up the calipers, making the pads more likely to wedge in the ways.

Looks for the fountains returning in the master cylinder reservoir, as I mentioned earlier in this thread

Sounds a bit like the ubiquitous "death wobble". First experienced it on 75 Chevy panel truck. Same with my 99 Cherokee. Starts when you hit a pot hole, and only stops when you get below 10-15 MPH.

Check anti sway bar, front end bushings and tie rods, steering damper. Steering damper was added to the 75 Chevy. Bushings on the Cherokee.

Brake fluid should be changed every 15 yrs or so. The calipers suck up water when hot and you drive through water.

When I see the price, I think "aftermarket"

When I think reliability, I think OEM

I have seen no mention of WHAT brake fluid he used. I would bleed the brakes using FRESH brake fluid, and make sure it meets DOT-3 specifications. Brake fluid tends to absorb moisture when exposed to air so buy a new can. Never use old brake fluid!

I got a brake bleeding kit which generates a vacuum when operated (available at Harbor Freight and other). It is definitely worth the cost because you no longer need a partner to do the "PUSH-RELEASE" BS. I am happy to say that this tool really sucks!

Please keep us informed of your progress.

Bill

He was asked about brake oil in #22 - no response to that question either.

The things we don't know far outnumber the things he has confirmed.

We don't know if the truck is equipped with rubber calf nuts or not.

Make 'Merika Great Agin.

The pin/rod in the brake booster which pushes on the piston in the master cylinder is adjustable ..... it screws in and out, I have had the brakes jam on when it was screwed out too far ...... if it is loose it may have screwed out with vibration, it should not be loose.

I'm just going to replace the whole booster

Good plan.

Please advise the forum of the result.

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Why is it nobody says, "we found the fault it was down to such & such", and let everyone know what was found, so many of these forums just fade away without a conclusion, or there is a conclusion but we never hear about it.

Bazzer.

Bad manners.

Usually coconditional with ill fitting footwear, myopia, cynophobia, and being a cheap tipper.

Last week my Right Front brake locked when I came to a country signal light, Smoked got hot, but when I backed up on the road about 20 yards it became free. I got it to a garage where it was checked out, service couldn't get it to lock again. So I go my truck back Friday 6/22/18 afternoon and driving it waiting for it to lock up again. It is 2015 GMC 2500 with 16,893 original miles, I bought new, babied, stays inside, it locked up the day before the service date for the warranty expired.

And the computer didn’t throw a code?

The brakes would certainly be suspect, coming to a stop at a signal, but what about front 4WD hub, or bearing?

5K miles a year does leave some opportunity windows for corrosion, condensate in lines, etc.

I had a house in Idaho, nat gas furnace. The furnace controller crapped out 10 years and 3 days after being installed and registered- 10 year warranty!

No Code.

Two wheel drive only.

bearing like new.

This sounds like a very durable (rock?) piece of debris was jammed into your brake. By forcing the vehicle to run backwards for 20 yards the debris was removed.

I am stunned you had a locked brake for 20 yards and your mechanic could not find any scoring or other abrasion damage somewhere after a dozen turns of a locked wheel. I suspect the scoring damage was actually on the disk but under the acceptable disk damage dimensions.

That sounds like a reasonable scenario and has a fair chance of being correct.

I rather believe the designed failure sequence would be one pad being scored in lieu of your suggested scored rotor disc being evidence of the event, this not being able to be inspected unless the calipers are disassembled.

It looks like he has left the building.

dcox88

Re: Brake Problems 06/23/2018 6:42 AM

Hopefully it wasn't due to brake failure.

Try this.

Hey, that was the Chick Magnet!

Always wondered what happened to it.

My advice is to give it one shot and take it to a good mechanic. If he can't figure it out, then it may be time to buy a new - newer truck. A 28 year old Chevy will most likely have a lot of worn out parts. Everyone here has given a good guess as to why it's having issues. Nobody really knows, so give your mechanic a last try and if he can't fix it, you know what to do. The other question is this: Is it worth all of your time and effort for a truck with very little value?