Rear brakes not grabbing
I am having trouble with my rear brakes not grabbing very well. I set up the rear on jack stands and could hardly stop the rear wheels with the brake pedal. My front brakes are in good condition and lock up in gravel, but not the rears. I bled the rear brakes with a pressure bleeder and the fluid came out with no bubbles. The brake pedal is firm. The master cylinder looks like the original. Can the master cylinder fail for the rear brakes? Could it be the proportioning valve built into the Kelsey Hayes 4wal ABS system? Could the proportioning valve have an isolation circuit that is stu
Experienced mechanics share their insights in answering this question :
Hello. It is not in the ABS, but may be the proportional valve not giving the correct pressure split front to the rear. The vehicle never had enough pressure for the rear brakes. Have the rear shoes adjusted properly if you have drum brakes. You should check to see if there is an updated part to replace the old one. If you would like to have this done, a certified technician from YourMechanic can inspect the brake system and let you know what repairs are needed.
How to Identify and Fix Common car Problems ?
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The most common causes of your brakes not releasing is a seized caliper or brake pad. This typically occurs due to rusting or ageing. Typically, you will notice your vehicle pulling to one side when you press down on your brakes.
Brake drag happens when the brake pads or shoes don`t release completely when the brake pedal is released and is typically a result of mechanical issues or hydraulics.
Cause of Two Wheel Drag
Residual pressure causing brakes to apply after brakes reach operating temperature. As a result, the most common cause for this condition comes from plugged or covered vent ports in the master cylinder.
If you are having trouble bleeding the rear brakes on your, it`s most likely due to a damaged proportioning valve. This valve manages and directs brake fluid to the rear brakes. When this valve goes bad, there will be little to no brake fluid being sent to the rear brakes.
The ABS is supposed to prevent your brakes from locking. The system operates through a computer in your vehicle to send messages when it senses unusual wheel decelerations. The computer reduces pressure on the wheel so the brakes will stop the vehicle. Brakes can lock up if your ABS system is faulty.
Either ABS is in pass thru mode where it does nothing or it is limiting the amount of force applied to a brake to prevent lockup, so no ABS can`t cause a brake to drag.
One of the most frequently encountered braking issues goes by the name of brake drag. Brake drag occurs when one or more of your brakes don`t fully release when you take your foot of the pedal. Brake drag may stem from a variety of underlying mechanical issues.
This stock proportioning valve has a residual pressure valve in it that helps to slow the rate at which the brake shoes relax from the drums. Unfortunately, this feature makes the rear-disc brake pads drag on the rotor-causing excessive heat buildup and pad wear, slowing the vehicle.
If brakes aren`t bled and air bubbles are trapped within the brake fluid, hydraulic pressure is greatly reduced, making the brakes less efficient. In addition, a condition of a spongy feeling brake pedal can exist as well.
You don`t have brakes! When the master cylinder runs dry or is rebuilt the air must be removed from the hydraulic system. The system will contain air which is compressible causing the need to pump the brake pedal.
If the ABS system is not functioning properly, then your vehicle is likely to skid, hydroplane and lose traction under heavy braking conditions. The last time you want to find this out is when you need it most in tough conditions, which could lead to an accident on the road.
A faulty ABS sensor will impact a number of important braking functions and will exhibit some obvious warning signs including: ABS light: this is normally the first sign that there`s a problem with the ABS system – this could be caused by either a sensor or the control module.
Here are a few possible causes and suggestions: Brakes need adjusting, or linkages need lubricating, or drums and linings need attention, or mechanical parts like rollers and cam shafts need replacing. Air pressure is too low.
The problem may only be air in the brake lines. If that`s the case, use a brake bleeder kit to bleed the brakes. You may also need to replace brake pads and replace or resurface worn rotors. While you`re at it, check the tires to ensure sufficient tread remains, then rotate them as needed.
Wheel speed sensors are often called ABS sensors. You`ll find them mounted on the axles of all ABS equipped vehicles. Look for this sensor on your wheel hubs, near the brake rotors. You`ll find the rear wheel speed sensor mounted on the rear axle housing or wheel cylinder.
Removing a wheel speed sensor will disable ABS—and sometimes, stability control. If your car has a yaw sensor, you can unplug that for results. You can also try simply unplugging the ABS module, though that could adversely affect your car`s braking performance.
Occasionally, these sensors can fail or become faulty working intermittently sending inaccurate signals to the ECU. In your case it may be possible that the transmission is receiving a faulty signal from the ABS system.
The ABS module will need to be programmed once everything is installed. This procedure also will vary quite a bit depending on the manufacturer. Tip: For this step in the ABS module replacement procedure, refer to the manufacturer`s instructions to find the specific programming procedure.
With so much vacuum pressure flowing through the system, this can even cause brake fluid to end up inside the booster, as can damage to the seals in the master cylinder.
It takes vacuum away from other components, and it can cause your engine to stumble, the RPMs to drop, and your engine could stall. The Check Engine Light can come on. Some cars are equipped with a brake booster vacuum sensor. If you have a leak, it can trigger the Check Engine light to come on.
Use a screwdriver to press and hold the plunger in the rear of the master cylinder. The plunger should be very firm, if not immovable, past a few millimeters. If the plunger keeps moving in, this indicates a fault of at least one of the internal seals.
If your brake pads are excessively worn, the metal backing on them can become exposed, allowing the rotors and metal to grind against each other when you brake. Not only does this cause an unpleasant sound, but it can also damage your rotor, reduce your brakes` responsiveness, and lead to brake failure.
Brake proportioning valves are the parts of a vehicle`s brake system that limit the amount of pressure reaching the rear brakes, which helps to prevent rear wheel lock-up, allowing you to stop your vehicle more safely and efficiently.
A Brake Proportioning Valve is commonly found on vehicles with front disc and rear drum brakes. It is a safety valve that restricts flow to the rear brakes during a “panic stop.” This prevents the rear wheels from locking up before the front wheels.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
Rear brakes not grabbing – 1995 GMC K2500
ANSWER : Hello. It is not in the ABS, but may be the proportional valve not giving the correct pressure split front to the rear. The vehicle never had enough pressure for the rear brakes. Have the rear shoes adjusted properly if you have drum brakes. You should check to see if there is an updated part to replace the old one. If you would like to have this done, a certified technician from YourMechanic can inspect the brake system and let you know what repairs are needed.
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Low brake pedal and anti-lock brakes are not kicking in.
ANSWER : The brake pedal is working to stop the vehicle, but there may be air in the controller unit causing the ABS brakes to not function. I recommend bleeding the brake system from the farthest location from the master cylinder to the master cylinder including the ABS unit. If the brakes are still spongy after a full bleed, then the controller will need to be replaced. If you need further assistance with your brake pedal being spongy, then seek out a professional, such as one from Your Mechanic, to help you.
Read Full Q/A … : Rear brakes not grabbing
Hard brake pedal and rear brakes locking up.
ANSWER : Hi. I will help you with this issue you are having with your 2001 Durango. Unless you bled the master cylinder, it is possible there is still air in the system. If you car is equipped with ABS, air could have also gotten trapped in the ABS modulator. If ABS equipped, a bi-directional scan tool would be essential to manually activate the ABS system to clear air from that segment of the lines while you are bleeding the system. It is also possible that in all of this work somehow the proportioning valve has been affected causing the desired pressure differential, front versus back, to get out of spec. Using a 2,500 PSI gauge, you can check the pressures at each wheel and that will definitely give you a clue as to which brake circuit is the issue (or both), whether the proportioning valve is working properly and whether the line pressures at each wheel are within spec. Should you need a second opinion, by all means feel free to contact YourMechanic for assistance and we will diagnose and repair the issue for you.
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Rear brake job
ANSWER : Hello, thank you for writing in. These situations are understandably questionable. The service providers at a lot of common oil changing and tire repair centers will quote you for a variety of things that can be updated. This does not always mean you are in dire need for more repairs. If braking seems to be harder, spongy, or takes longer, then you have reason to be concerned. Otherwise, you should check the amount of brake pad material left on the calipers. This can be visually inspected without too much trouble. Remove the wheel and physically measure the amount left, compare them to your vehicle specifications. It is a little early to worry about brake fluid or the rotors. However if the brake fluid is low, the rotors are warped from a hard stop, or there are obvious issues you should look into the system further. Only further inspection will confirm or deny the recommendations. For a second inspection, contact our service department to schedule an appointment.
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Changed brake master cylinder, bled 10 times, and the pedal is soft The rear brakes are not locked but close. Truck now running rough.
ANSWER : You will have to bleed the brakes from the farthest location all the way to the master cylinder. There is still air in the lines causing the issue. Check the vibrations on the vehicle to see if the engine mounts are damaged or if the brakes are not releasing causing the engine to run harder than normal to overcome the braking force. If you need further assistance with your vehicle’s brake system, then seek out a professional, such as one from Your Mechanic, to help you.
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EPC light on 2004 Jetta. Code said brake switch faulty, but brakes lights worked. Replaced brake switch, now no brake lights.
ANSWER : Hi there. The first thing that pops in my mind beyond of what you have listed is perhaps the electrical harness attached to the brake switch. Perhaps the harness itself is damaged or you have an exposed wire, loose ground wire somewhere. You might want to have a professional mobile mechanic come to your location and complete a brake lights not working inspection to help you diagnose this issue.
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When I put my foot on the brake my back left brake light goes off, when I take it off the brake the brake light comes on
ANSWER : I would suggest trying to disconnect and reconnect the wiring to the rear lights. I have seen these older Toyota vehicles rear lighting short out on the lights themselves due to the way the light circuit was made on the lamp housing. Look at the housing circuit on the light to see if one is touching another, and that could tell you why it is malfunctioning. There could also be a problem with the brake light switch. If you are not comfortable dealing with wires, I recommend getting in touch with a certified mechanic who can look at your brake light issue for you to see what’s going on.
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No brake fluid is getting to the rear brakes
ANSWER : As far as the brake issue, yes, there needs to be a check to see if there is brake fluid entering into the proportional valve. If there is fluid supply to the valve but not out then the valve will need to be replaced. Any electrical faults in the rear ABS system are generally indicated with a light illuminated and if so, then the flash codes can be read out. But with no light illuminated then there most likely no electrical failures in the system. If the source from where the brake fluid supply cannot be located, then you may want to enlist the help of a mechanic, such as one from YourMechanic, to help with the diagnosis of your brake system.
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