When I first test drove this truck, I rolled down the dealer's driveway and stopped at the road. I pushed the brake pedal down, further, further, and then the truck almost locked up. It never did it again during the test drive. Now, I notice that if the truck sits for a while without being driven, when I back out of my driveway, it does the same thing for the first stop, but by the end of my street, it is fine. Is this a diesel thing?

If you're talking about the brakes locking up, yeah it's a typical GM thing I think. May be caused by leaking seals, but I've never verified it myself. My truck only does it after it's been driven in the rain and allowed to sit for a while. The next time I take off in it, I better go easy on the brakes the first time or two I use them or else they slam pretty hard.

I believe he thinking on the pedal traveling further than he likes. Might want to check the Master Cylinder for that and as far as locking up, I notice that more when the axle seals or wheel cylinders are leaking and the brakes covered with grease.

[QUOTE=bowtie]I believe he thinking on the pedal traveling further than he likes.QUOTE]

Not really, just that when I press the pedal the first time after it sits a long time, the brakes practically lock up...then it is fine. Sorry, I described it poorly. :)

[QUOTE=bowtie]I believe he thinking on the pedal traveling further than he likes.QUOTE]

Not really, just that when I press the pedal the first time after it sits a long time, the brakes practically lock up...then it is fine. Sorry, I described it poorly. :)check the rear axle seals for leakage and the brake shoes for contamination from read end lube.

This vintage GM truck has effectively no rear brakes even on the best of days.
What I would check is the slide surfaces on the front calipers and the caliper pistons. What it may be is the front system is sticking over time and as you apply the brakes all pressure is feed to the rear which are not going to work anyway. Once the rear brakes bottom out that would cause the front to brake loose and than have a suddent application of the system that does work thus acting like a lockup.
If you ever get rear brakes let us me know because I have been chasing that goast for 6 years.

HUM I always have rear brakes on my trucks at least the ones I drove starting in 1984. Now I agree they don't do much work when empty and work better when loaded, They do tend to show their ugly side when used in rain and snow or ice. Even my current truck has acted the same way and when they tend to lock up under light braking apps. I have always found either a rear seal blown or improper adjustments or something else wrong back there. I haven't had lock up problems when nothing was wrong or my big foot wasn't to blame. Just my .02 cents and a good thing to make sure is correct before looking else where.
NOW if all 4 are locking up then other things should be looked into and if, as he described, that the pedal goes to the floor after sitting for awhile then i would look hard at the master cylinder for bypassing internally.
There thats about .04 cents worth together

Perhaps the hyrolic fluid is cold in the powersteering pump.

[QUOTE=kl8tonNot really, just that when I press the pedal the first time after it sits a long time, the brakes practically lock up...then it is fine. Sorry, I described it poorly. :)[/QUOTE]
I had a 99 F-150 that did that from new. The dealership put two sets of shoes on the rear that did not help. Their 'official' word was the non-asbestos linings used would absorb water and expand. After a stop or two the heat would run out the moisture and all was fine. Later '99 and since the went to rear disks to solve the problem.

There's a carving on the front wheels (wheel bearing?) around the side of the piece where the wheel bolts stick out. The metal plate of the brake pads is running within the carving so that it doesn't grind into the piece with the wheels bolts.

If brake pads have been installed that do no exactly fit, they can grind into the metal they sit around. I don't know what happens when the pads are worn so much that their metal plates would go further to the brake disk than the carving allows them to. It looks that they would start to grind at the inner side of the carving long before the metal nozzle which should make a squeaking noise to indicate worn pads comes to touch the disk.

How should one know when the pads are worn?

Maybe your brake pads are worn, or the pads don't fit.

That carving is rotor wear. Buy a new set and you'll see it has no carving.

my truck does the same thing. most mornings it is fine, but somedays it will bout throw you threw the windshield the first time you hit the brakes.

QM, which part exactly is the rotor? I'm in lack of knowledge and terms on the brake parts, and it's difficult to describe the part I mean.

The part I have in mind is the part where the wheel bolts stick out through. When the wheel is attached/mounted, the rim sits on the outside of that part and the wheel nuts press it against the outer front side/dish of that part. On the other side of the part is the brake disk. I think the part must be looking like a bowl if you take it off. The brake pads are curved, and they curve around the outer side of the part, about where the carving is, and from there, they go further to the brake disks.

The carving looks as if it was maschined into the part when it was manufactured. The sides of the carving are even, and it is of the same depth all around. To make such a carving, you would have to cut it into the metal on a lathe.

There seems to be nothing at the brake pads that could make such a carving. The pads move alongside the part I'm failing to describe, they do not move sideways into the part (unless something goes serioulsy wrong) to make a carving like that.

The carving is rusted like the rest of the part, so it doesn't seem to get carved deeper. But if you cut it deep enough, the part (bowl) will fall apart which would probably lead to very bad results ...

Are you sure that is normal wear?


PS:

Something like this one, there's also kind of a carving where the break pad goes, but very close to the disk --- looks intentional to me, not like wear. But the brake bad is so thin that it fully fits into the carving, not only the metal plate:

http://www.agnes-maurer.de/Content/ritmo/f138/br_ha5.jpg

Olee
It is highly unlikely that pads that did not fit could ever be install on disc brakes. The pads are closely fitted to the mounts at the top and bottom of the pads, usely have to be pushed in by hand to bottom out in the mounting frame.

As for notification over ware, the original and any good quality replacement will have what is called a squeeler, a thin strip of metal supended at the lower ned ot the pad, that when the pads ware down to a point of replacement will sound a squeel every time you apply the brakes. Don't panic you still have a couple hundred miles of safe travel before you have worn the pads down to the point of doing damage to the rotors.

As for the grove you mentioned I am not sure what you are discribing. The surface of the rotors that come in contact witht the pads should be marble smooth. If there are groves in this contact surface the pads have damaged the rotors sometime in the past. Any groving outside the contact area is most likely an original machining cut.

Howie, someone managed to install brake pads on mine that didn't fit, before I got the truck. The metal plates of those pads were a bit too large. I was lucky that it was noticed and corrected early enough by grinding the oversized metal of the pads away, almost a year ago. Just two weeks ago I got new pads because the old ones were worn. The old, not fitting ones were even a bit longer than the new ones, and they lasted more than 80kkm with enough of the pad left to do no damage to the rotors ... Braking power has much improved since then.

The new pads have squeelers. But I'm not sure if the pads will, when worn, go down onto the rotors far enough to make the squeelers touch the rotors because the metal plates of the pads are sitting where the carvings are. The carvings give room for the metal plates not to touch the 'bowl'. After searching for a better picture, now I think the 'bowl' and the rotor is one single part, i. e. the brake disk.

The rotors have many small grooves in them that usually come from normal wear. The carving is not in the rotors but in the 'bowl', and it looks as if it has been cut intentionally to give way for the metal plates of the brake pads, at least at the time when new pads are installed. The pads might settle over time so that they never touch the 'bowl'.

Maybe the people here with 'sticky' brakes have brake pads installed that do not exactly fit. They could sometimes touch the 'bowl' or so, somethimes not. Taking off the wheels and inspecting the 'bowl' and the pads could show if the pads touch something they should not.

Ollee

Can you get a picture of what you are discribing and e mail it to me or post it here if you know how so we can see whats up. My address is in my signature.

Here's a slightly rusted but other wise new rotor for a k3500. The center bearing(hub) attaches to it via the eight lug nut stems. Knock them out and it's free.

A bad ball joint helped shake the lug nuts loose and the soft aluminum wheel on the '96 lasted seconds before detaching at 65 mph and destroying this two week old rotor. o'riellys was kind enough to sell me the replacement pieces at half price to lesson the blow of repairing all that.

That was really bad luck, QM :/ I hope the damage wasn't all too much and nobody got hurt! Thanks for the picture, though!

Howie, to take a picture I'd probably have to take a wheel off. Maybe I can peer through the spaces of the rim --- if I can, I'll make a picture.

The rotor on mine looks a bit different from the one on QMs picture, but it also has the center bearing hub like his. The carving I mean runs around the center bearing hub --- QMs rotor isn't carved.

Olee

If you are saying that there has been a groove cut into the vertical wall between the rotor and the stud mounting face and that groove is of any depth I would consider replacing the rotor to prevent it cracking off during heavy braking and realy causing a problem.

Pads that are the right size should never move enough to have come in contact with that part of the rotor.

Still a picture would insure we are all talking about the same thing.

Sounds to like you might want to investagate a little more. That groove could be a problem.

Howie, I think that's what I was trying to say :) I'll try to take the picture tomorrow --- it always gets dark too quickly these days ...

Hm, new rotors would be $$$ :/

Well, I tried to make some pictures today, but we were having one of those foggy days that don't get bright all the time. The outcome is unusable: