Mechanics

VIBRATION WHILE CRUISNG, WORSE AFTER BRAK

2003 Honda Accord

Shakes or Wobbles problem
2003 Honda Accord 4 cyl Front Wheel Drive Automatic 80,000 miles

Under 45 MPH the car drives perfect. Once speeds go over approximately 45 I get a very slight vibration in the steering wheel and hear a humming/propeller sound from the front. The higher the speed the faster the sound. Wheel balancing doesn't help. Thinking CV shaft or wheel bearing.

Also, after hard braking from highway speed the steering wheel has an almost violent vibration and the humming/propeller sound is very loud. This is after I release the brake pedal so I'm thinking it isn't the rotors.

Please help, I can't stand these problems anymore!
Avatar
Zionswrath
February 27, 2010.



The buzzing suggests a noisy wheel bearing. Very often it will become quiet or louder when turning a little such as when changing lanes. The noise will resemble an airplane engine. The half shafts won't make this type of noise.

Suspect a sticking brake caliper for the severe shaking after braking. Stop on a slight incline, put the transmission in neutral, then release the brake. The car should roll ahead on its own. If it doesn't, place a block a few inches downhill from a wheel, then open one of the front caliper bleeder screws. If you see a little spurt of fluid and the brake releases, a front brake hose is constricted or the fluid is contaminated with petroleum product. Fluid contamination will show up as the rubber seal under the cap of the master cylinder reservoir is blown up and mushy. Constricted hoses are rare, but are usually caused by rust buildup under a bracket that holds the center of the hose or under the crimped fittings on the ends.

Caradiodoc

Caradiodoc
Feb 27, 2010.
There is no play in the wheels and I don't know of any other way to make sure it is a wheel bearing. Can you suggest anything? I don't have a lot of $ so I want to fix it right the first time.

I don't know when the car had a brake fluid change/flush so would this service help any? I check the reservoir cap and it is fine, bone dry and looks brand new but the fluid doesn't touch the cap and there is a strainer thing so I can't see the actual fluid. And I don't understand how I would open the bleeder screw with the car running in neutral on a hill.

Tiny
Zionswrath
Feb 27, 2010.
" Very often it will become quiet or louder when turning a little such as when changing lanes. The noise will resemble an airplane engine.&Quot; If your car uses pressed-in wheel bearings, the noise will get louder when you change lanes away from the bad bearing. If you turn toward the left lane and the noise gets louder, it's the right bearing. It gets louder because of the weight transfer onto that side of the car. You can also jack the front end up, run the car in gear, then listen next to each bearing with a stethoscope. Sometimes it's hard to tell that way because there is no weight on the bearing.

Some cars use easily replaceable but more expensive bolt-on bearing and hub assemblies. It is impossible to tell which one is making the noise with a test drive. It is REAL common for the sound to come from the right side, (for example), get louder when turning left, and it ends up being the left bearing. The good news is if you change the wrong bearing, you can put the old one on the other side of the car. Pressed-in bearings must be destroyed to remove them. To know for sure which bolt-on bearing is causing the noise, you must listen with a stethoscope.

An alternative to the stethoscope is to use a " chassis ear". That is a set of microphones that are clipped on near the suspected causes of a noise, then you drive the car and listen with headphones while switching between the different microphones. Moving the microphones around until you find the loudest point will help in finding the cause of the noise.

Don't expect the noisy wheel bearing to have looseness or free play in it. Once the noise starts, it can go on like that for years before it wears loose enough to detect by wiggling the tire. The noise is coming from a rough wear pattern on the rolling surfaces of the ball bearings. This can be caused by a hard impact such as hitting a curb, but it will take a while to show up. Normal wear due to age is the most common cause, but another often overlooked cause is supporting the vehicle's weight on the wheel / tire while the axle nut is loose. The bearing is held together by the outer cv joint housing and axle nut. It's not even necessary to move the car with the nut loosened or removed. Simply putting weight on it is all it takes to make it noisy. This is one common problem do-it-yourselfers cause if they aren't aware of it.

You don't have to have the engine running when looking for a stuck brake caliper. You can do the same thing by jacking up the front of the car and looking for which wheel you can't turn by hand. If opening a bleeder screw releases the brake, it is because fluid was trapped and couldn't make its way back to the reservoir. You can do the same quick check in a sloped parking lot OR, you can get up and try to push the car by hand each time you open a bleeder screw. The reason for the tire block a few inches ahead of one tire is to give the car a chance to move so you'll know when the stuck brake released, without the inconvenience of jumping up and chasing the car down the hill! A slight incline is sufficient. You don't have to park on a steep hill. This trick works well for stuck parking brake cables too.

I suspect you are going to find you simply have a locked-up front caliper for a couple of reasons. First, petroleum contamination of the brake fluid does not seem probable. Other than the occassional owner pouring power steering fluid into the brake fluid reservoir, two common causes of contamination are using oily fingers to reseat the bladder seal in the cap, and wiping out a funnel used for engine oil or transmission fluid, then using it for brake fluid. The slight residue of petroleum product in the funnel is all it takes.

To prove to my students how extremely important it is to keep the brake fluid clean, I put two wheel cylinder lip seals in two glass beakers partially filled with brake fluid. To one I added a single drop of engine oil and stirred it up. After one week, the second seal had grown by about 10 percent and was very soft and mushy compared to the seal in clean fluid. The rubber composition of brake parts is not compatible with any petroleum-based product.

As soon as you press the brake pedal in your car, the first thing the moving seals in the master cylinder do is move past the fluid supply ports blocking them and trapping the fluid. Continuing to move the pedal and seals is what pressurizes that trapped fluid and sends it to the wheels. When the contaminated seals in the master cylinder grow, they expand past those ports and keep the fluid trapped. When you apply the brake, heat is generated and transferred to the fluid which heats up and expands. Normally the fluid would just expand up into the reservoir, but since it's trapped and can't release, it keeps the brake applied. That generates more heat, the fluid expands some more, and the cycle continues until the brake is stuck so badly, the car won't move or a plastic wheel cover melts. The ONLY acceptable repair for this problem is to replace every rubber brake hose and every component that has rubber o-rings or seals in it. The steel lines must be flushed and dried too. Any rubber part that is overlooked will leach cotaminants out into the new fluid and the new parts will again be contaminated. This includes calipers, rear wheel cylinders, combination valve, master cylinder, reservoir, and cap, hoses, and heaven forbid, the anti-lock brake hydraulic unit if you have one.

Some manufacturers support the middle of the front hoses with a tough steel strap that's crimped around the hose. Rust buildup eventually squeezes the hose closed. Fluid can be forced through it with heavy pedal pressure, but it can't release properly. That's an instance where opening the bleeder screw will release that caliper and send the car rolling. I think your car uses a metal bracket with a rubber grommet to support the middle of the front rubber hoses, so hose constriction is not a very likely possibility. For that reason, I suspect you have nothing more wrong than a stuck caliper. If that is indeed the case, opening the bleeder screw will not release it. Additionally, brake fluid will flow freely out of the bleeder screw if the reservoir cap is loose. That is proof too that fluid contamination is not likely. The cap usually must be loose because fluid leaving the reservoir will cause a vacuum buildup that prevents the fluid from flowing.

You should be able to easily pry the pistons back into their calipers with a flat-blade screwdriver. If you can't unless the bleeder screw is opened, fluid is trapped and can't release back to the reservoir. If the piston won't move, regardless of the bleeder screw being opened or not, it is stuck due to dirt or rust buildup on the sealing surface of the piston. We used to rebuild them as part of most brake jobs, but today a professionally rebuilt caliper with a warranty doesn't cost much more than the kit to rebuild one yourself. It's a good idea to replace both calipers at the same time to insure even stopping forces.

Every manufacturer recommends a specified interval for flushing and replacing the brake fluid but no one does it. It's normal for fluid to turn a dark brown color from being hot. That alone doesn't affect its performance, but it suggests it has been in the system a long time. Moisture works its way in past lip seals and believe it or not, through the pours in the rubber hoses. Moisture will lead to corrosion of metal parts and it will reduce the fluid's boiling point from over 400 degrees F. To 212 degrees. When the fluid gets hot, the moisture will boil and form compressable bubbles. That's a major cause of brake fade and repeatedly finding air in the hydraulic system with no obvious indication where it's coming from. Containers of brake fluid should always remain sealed when not being used to prevent the fluid from absorbing moisture from the air. For your symptoms, replacing the brake fluid will not solve anything, but it could delay the onset of future corrosion-related problems. It's cheap insurance that is done unwittingly when replacing parts in the hydraulic system, (such as calipers).

As long as I'm covering everything I can think of, I might as well include one more seldom-known tidbit. Under normal operation, the brake pedal never goes further than halfway to the floor. That moisture in the fluid causes corrosion and debris to build up in the bottom halves of the two bores in the master cylinder where the pistons and seals don't normally travel. Anything that causes the brake pedal to go to the floor will run the lip seals over that crap ripping them. That results in internal leakage and a pedal that sinks to the floor when the brakes are applied. It is real common for do-it-yourselfers and beginning students to push the pedal all the way down when bleeding the hydraulic system. Before they ever touch a car, I warn them to pretend there's a block of wood under the pedal, and NEVER push it past half way. Customers can push the pedal too far when they're surprised by a sudden leak such as a popped rubber hose or a rusted steel line. As a mechanic, I always explained what could have happened to their master cylinder and that a new one might be needed along with the replacement for the leaking part. It's better to be warned and prepared up front than to fall into the " since you have your wallet open, you also need, ... &Quot; syndrome.

Caradiodoc

Caradiodoc
Feb 28, 2010.
I took apart the front driver side brakes and found one of my pads had a crack in the middle and they are missing material on the sides.

Would this be indicative of a sticking caliper? I cleaned and lubricated the slide pins and the pin holes but haven't driven it but I doubt that would fix it.

What should I do?


http://www.2carpros.com/forum/automotive_pictures/491237_P6050116_1.jpg


Tiny
Zionswrath
Mar 5, 2010.
I listed a whole bunch of stuff. Took an hour to type that goodness. Did you try any of the suggestions?

Cracks can develop in the linings from heat. That alone is not cause for replacement. Compare the lining thickness to the pads on the other side. Sometimes calipers tend to stick when the linings near the end of their life. Before removing the caliper, did you try to pry the piston back into the housing? If you tried but it wouldn't move, did you open the bleeder screw to allow it move easier? What was the result there?

See those 3/4" wide tabs on the ends of the pads' metal backing plates? Those should also be lubricated to reduce sticking.

Caradiodoc

Caradiodoc
Mar 6, 2010.
Here is what I did.

I tried to push in the piston. I don't have a C clamp so I used a wrench to pry through the hole in the caliper. I tried using a screw driver but I did have any luck so I moved to something thicker. I had to open the cap under the hood as well as the bleeder screw and I was only able to push the piston in about 1cm. Maybe if I had a C clamp I could have to do it all the way?

I turned the car on while in neutral and before I pressed the brakes the the rotor was spinning. I pressed the brakes a few times until the piston got into contact with the brake pads and then only the passenger wheel was spinning. I put the car in drive and pressed the gas a bit and still only the passenger wheel was spinning.

I opened the bleeder on the driver side with the car in drive and that didn't do anything.

Tiny
Zionswrath
Mar 6, 2010.
The top caliper slide is difficult to move in and out by hand even after cleaning and lubrication. When pulling the slide outward the rubber boot collapses as if there is a vacuum inside.

Tiny
Zionswrath
Mar 6, 2010.
I don't think you found too much unusual there. The pistons should move in fairly easily with a screwdriver. Bigger is ok too, but you should never HAVE to resort to a c-clamp. I know a lot of books show doing it that way, but only because most people already have the caliper removed when they start looking for a way to retract it. If the piston can not be forced in any other way than with a c-clamp, there's no way its going to release after normal braking either. That is cause for replacement. We used to rebuild calipers all the time during regular brake jobs, but store-bought rebuilt calipers used to cost over 90 bucks. Pistons needed to be replaced if there was any sign of rust pitting, but they were only 20 bucks. Today the piston is still 20 bucks, the rebuild kits are still around ten bucks, but a lot of good quality rebuilt calipers cost less than 30 bucks.

Since there was no change when opening the bleeder screw, that implies blockage of the hydraulic system is not a problem. When opening the bleeder and master cylinder cap helped, it was likely just because you were trying to move so much fluid and the cap was sealing so well, the air couldn't escape.

Moving the piston 1 cm is quite a bit. It only should go in far enough to make sufficient room for new, thicker pads. Most professionals retract pistons this way, (screwdriver), before they remove calipers during routine brake service.

As for the wheels spinning, it's hard to draw definite conclusions although it does kind of sound like the left caliper is sticking. One front wheel will always have less resistance to rolling when run jacked up like this, but it isn't a good indication of how it will act on the road. The next step is to put it in neutral to stop the right wheel, then block it from spinning. If you have vented rotors, just stick a screwdriver through the caliper into one of the vent holes. When you put it in " drive", the left wheel will be forced to spin. If it really resists spinning, or stops quickly after letting off the gas, that caliper is still tight.

One word of warning I often fail to mention; never push the brake pedal all the way to the floor to move the pistons out to the pads and rotor. It's good you understand it's necessary to get the pistons out there before driving, but most people are not aware that corrosion and debris build up in the bottom halves of the two bores in the master cylinder where the seals don't normally travel. By pushing the pedal all the way down, the seals can easily get cut on that junk. That results in a slowly sinking pedal and failure of at least one of the hydraulic circuits. The only fix is a rebuilt master cylinder.

Ok, as for the mounting pin with the collapsing boot, the vacuum just suggests it is making a seal that will be effective at keeping water, dirt, and salt out. Under normal operation, the caliper will only move the thickness of the inner pad lining, over the life of the pad. Of more importance though is after the brakes are released, the caliper will try to slide away from the center of the car just a little to release pressure on the outer pad. Failure to do that will result in the outer pad wearing much faster than the inner pad. (Sticking of the piston will result in rapid wear of BOTH pads compared to the other side of the car). Those mounting pins must be free of rust, pits, corrosion, and impacted dirt. In other words, they must be clean and shiny, then have a light film of high temperature brake grease applied. As long as you can move the caliper by hand, the mounting pin should be fiine. If you need a hammer to move the caliper, you've found a problem!

From everything I've read, my suggestion is to replace the left caliper, but to insure even braking forces, it's always best to replace both at the same time.

Caradiodoc

Caradiodoc
Mar 6, 2010.