Stuck and Hesitating Acceleration

Re: If I leave off the brake, pause, then accelerate it doesn't do it.

I'll start with a question--what is your normal practice--do you do anything like use the left foot for the brake (and the right foot for the accelerator)?

If not, do you typically move your right foot from the brake to the accelerator very quickly, and then accelerate hard?

Did you replace the brake hardware, too? Like the return springs for the shoes? Pads are for disks. Shoes are for drums.

Pads don't have return springs. Shoes do.

try dis-connectting. the emergency cables where the connect to the brakes. it sounds like something is sticky and needs a few seconds to fully release. clean off the rust and grime on all the moving brake parts, then put on a light coat of high temperatuire grease. only use a silicon spray rubber parts

I don't think it's a good idea to use grease or silicone spray anywhere around the brakes. All it would take is a little on the drums, and stopping would become the problem.

Clean brake parts...........YES

Lubricate brake parts.......NO

For the parts that move, the brake fluid is the lubrication.

To the OP. I have an older GMC truck. Do your rear brakes have the self adjusting star wheel? If so, the internal threads would be the one thing that you would want to put a very light coat of grease on.............No grease outside the cylinder.

If they do still use the star wheel, this may be the explanation, they are designed to self adjust until light pressure is on the drum.

they do make lubricating products designed for brakes, including grease and silicon spray.

I worked in the automotie field for over 25 years. It was not common but I did replace between 15 and 20 brake hoses, (front and back) that resolved the exact problem you have describe.

Good answer Smoothy

GA! The first time I ran into this I thought the guy telling me was ready for one of those funny jackets, but now that I've experienced it on 2 vehicles, I believe it.

For those who have not experienced it, there are no return springs on disc brakes, so the slightest restriction prevents the pads from retracting. Disc brakes also require more hydraulic pressure, so the restriction in the hoses is not noticeable when you apply the brake, just when you release it. Try getting up to speed on a clear road. Step hard on the brake, then release and see if the brakes still seem to be on. be careful, one hose having a problem on the front may cause the car to veer off to the left or right when you release the peddle pressure. -- JHF

More than likely the shoes are sticking and are not releasing on their on and are sticking and when you let off it allows the drum to back off just the slightest amount which is allowing them to release. I would take the rear drums back off and clean all of the parts on the backing plate very throughly and put a new hardware kit on the rear brakes. Could you have put the shoes on in the wrong position with the front shoe on the rear as the friction pads are different lengths and if they are backwards them the shoes will hold on the drum as they will not release correctly. If you put new drums on the rear did you throughly clean the friction surface as the anti corrsion coating will turn gummy when it gets hot as it would when you apply the brakes. Hope this helps.

Usually, whenever I have done rear brakes, I apply high temp grease (made for this application) between the sliding surfaces of the backplate and edge of the shoes.

I also do the same thing with caliper pads. The sliding areas need to be lubricated or they might stick.

You do not want to get any kind of lubricant on the pads & rotors, or the shoes and the drums. Use a non-oil based cleaner (made for this) to clean them.

I have never had a problem with brakes.

As said before, a sticking emergency brake cable could be an issue as this has happened to me before.

The joy of coming late to a discussion is that I get to see what others are thinking. My two cents would be a combination of checking the self adjustors (the star wheels) to make sure that they work freely and that the mechanism is installed correctly. This job is first up simply because it is the easiest to do, esecially if you have had the drums off to replace the brake shoes already.

Once that is done my second item to check is the emergency brake cables and if they need replacement you have a head start on the job by having the wheels and brake drums off. Here in our harsh operating conditions, e brake cables are considerd fast moving parts. Every GM truck I have ever owned has had one or both cables corrode, seize or break, regardless of how often the e brake is applied. And, yes the warning is that it drags a bit when released.

My only other comment would be that you should use a good pair of mechanics gloves when doing this work. Brake dust and other corrsion can be tough to get off you hands and they will ensure that you do not leave any of your hands on the brake parts!!

Does any similar hesitation happen while driving, just after releasing brake? It's hard to notice if you don't intentionally try. If yes possibly a sticky cut-off switch (just over brake pedal near brake lights switch) S.M.

Pepperdan,

Your problem is either the e-brake self adjuster or perhaps a sticky wheel cylinder. both are fairly easy to fix. I would also clean all brake parts.

Rear discs, or drums? What has changed since the last time that the brakes were correct?

Weather you have discs, or drums, it is important to have proper clearance between friction material, and rotating parts. On drums, too much clearance can allow the shoes to self energise to the point that the shoes will return to the "at rest" position. On disc brakes, there is no return of the pads when the brakes are released. The only thing that changes is the pressure applied to the brake pads. If the brake caliper is not free to slide as the brakes are wearing, and then reapplied, the caliper may be twisting on the frozen slide, and sliding on the other one. This will wear only part of one of the pads. And because the caliper is twisting to make the pad grip the rotor, when the brake is released, the caliper will have to untwist to release the pad from the disc. This also will cause a slow release of the brakes.

There is a way that you can check for these as well as the bad rubber hose problem. Try this. Place good wheel chocks in front and back of both rear wheels. Make sure you are on level ground, and have a reliable helper.

With the parking brake released, remove the cover from the master cylinder. Have the engine running, in park. Have the assistant push the brake pedal down SOFTLY. Then watch the surface of the brake fluid in the master cylinder as you have e the assistant release the brakes. Be careful, the fluid is going to be pushed back from the wheels to the master cylinder. If the assistant was pushing too hard, the fluid will have some force behind it. This fluid will remove paint if it lands on painted surfaces. As you watch the fluid returning, compare it to the time that it took for your brakes to stop dragging. The longer it takes for the fluid to stop returning to the master cylinder, the more the wheel cylinders or caliper pistons are traveling each time you step on the brake. If you have a bad brake hose, the return of fluid will be very slow, and continue for as long as it takes for the dragging to go away.

If pushing softly does not make fluid fly out, you can push a little harder at each time, until the fluid is just manageable. Adding fluid to the highest acceptable level will also minimize the fluid splashing. If fluid comes out of the master cylinder, you can rinse it away with plain water. Just do not let water get into the master cylinder. If that happens, you must remove all of the brake fluid, and replace it with new DOT 3 or DOT 4 brake fluid. Good luck.

Sounds like a hydraulic issue, as it was noted in previuos post replace your flexible line in the rear as it is failing internally. The pause allows the the trapped fluid under pressure to leak by the failed area allowing the rear drum springs to pull the shoes away from the drums until the next stop

.

Thank you all for your input, I really appreciate it. I use my right foot on gas and brake. I also accelerate hard, kind of have a lead foot. when I bought the drums the NAPA fella suggested the hardware kit, which I picked up and have, but didn't put on. When I replaced the drums (shoes already replaced) it seemed to work well for a short period, so for simplicity sake, I am putting the new hardware on this weekend. I'll try the suggestion from Bob to measure the rate of backfill to the master cylinder. I never use the parking brake, not sure if that makes any difference or not, but I can't remember the last time I've applied it. I'll let you know how it turns out, thanks again.

if you've never used the parking brake, then i would guess that the rubber flex hoses should be change as others have already suggested.

Try the parking brake. The self adjusting mechanism will not adjust as well when the brakes get thinner. If you apply the parking brake, and it is very low, it is time to remove the rear drums and inspect the linings.

This is not your concern now, but it is a good practice to use just as a tool to monitor the rear drum brakes. Good luck.

This may sound obvious but be sure the shoes are on correctly...that is to say looking at the drum from the side, there's a correct one that goes towards the front and a correct one that goes towards the back.

Hi guys, I do not post often unless I feel I can help. Not Knowing The poster excuse me If I may insult your knowledge. My 2 cents. Sounds like every brake broblem has been addressed except the vacuum valve on the booster or a very soft hose to it. Or The booster/ckeck valve/ hose leaking vacuum or something causing fuel pressure reg to get such a late vacuum signal (or it's bad) that when accelerating there is high vacuum already there it just keeps dumping fuel pressure and does not close to insrease fuel preasure (to go.) Just a suggestion. We all know the fuel pressure regulator is not controlled my the computer, Just by high and low vacuum it gets it signal from the manifold. High Vacuum low Fuel Pressure, Low Vac. High Fuel Pressure but look for something simple. Old crached hoses, soft hoses ect. A fuel pressure gauge, if avaiable will tell a lot. Even with vice grips, crimp the return line. I hope I'am not being reduntdant or overlooking something you guys already tryed. Good Luck. If I am out of line let me know as I'm rusty on some of this new ,old stuff Regards Autojay

I concur with most other posts, check the hoses/brake lines...if one of the lines feeding into the hoses is kinked it might cause a problem releasing the hydraulics. Here is how it is, great pressure is forced through the lines, if there is a kink it will still flow through. However, if there is a kink the return will be sluggish because there isn't much pressure pushing back to the master cylinder. Maybe you scrapped the bottom of the vehicle and damaged a hydraulic line. Maybe the brake hoses are deteriorating.