Brakes have little to no pressure to wheels
The brakes have little to no pressure to any of the wheels. I checked for leaks with another mechanic who couldn't troubleshoot to resolution. Could it be a problem with the master cylinder?
Experienced mechanics share their insights in answering this question :
Hello! We must first determine the possibility of air entering the system. Air is the enemy to any working hydraulic system as well as moisture(water if the system is filled with oil). Though you may not have found fluid leaking out, air may have found its way in. The braking system should be bled completely first, then the master cylinder may come up suspect. Have a mechanic, like the ones we have to offer here at YourMechanic, assist you with the brake pressure problem.
How to Identify and Fix Common car Problems ?
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Air in the brake line(s) is the most common cause of a soft/spongy brake pedal. If air gets into the brake lines, it can prevent brake fluid from flowing properly, causing the brake pedal to feel spongy or soft. If the brakes are soft or spongy, this is a good time to change or flush the brake fluid.
1) Line pressure can only be increased by either increasing the mechanical pedal ratio or by decreasing the master cylinder diameter. In either case the pedal travel will be increased. 2) Clamping force can only be increased either by increasing the line pressure or by increasing the diameter of the caliper piston(s).
In most cases, stiff brakes are caused by problems with the brake booster. Brake boosters multiply the force applied to your brake pedal, and they work in tandem with the hydraulic fluid in the brake lines. This system, also known as power brakes, allows you to stop a two-ton vehicle with just your foot!
Air in the brake lines is one of the most common causes of spongy brakes. Braking systems rely on evenly distributed hydraulic pressure to bring vehicles to a halt. Air in any of these lines can throw off this balance of pressure. Poor pressure can result in more time, distance, and/or effort to stop.
The most common reason for a soft brake pedal is simply air still in the system. The easiest way to diagnose this problem is to pump the brake pedal gently a few times. In doing so, the pedal should become firmer with each gentle press of the pedal. If it does, then the necessary answer is bleeding the brakes.
The easiest way is with the brake pads in situ. Simply push a flat blade screwdriver in between the brake pads and twist. This will separate the brake pads and, in turn, push back the pistons to the reset position.
A malfunctioning Anti-lock Braking System (ABS) can also cause a hard brake pedal. The ABS system is responsible for preventing the wheels from locking up during emergency braking. If the ABS system malfunctions, it may cause a loss of hydraulic pressure, resulting in a hard brake pedal.
The classic symptom of a failing master cylinder is a brake pedal that “dives” or sinks slowly to the floor while pedal pressure is being applied. Another sign to look out for is any leaks around the master cylinder. If a seal is worn out, it may leak past the seal and onto the pushrod that attaches to the brake pedal.
These could be some reasons you have no brake pressure after bleeding your brakes: Air in the brake lines. Brake fluid leak somewhere in the system (check your fluid level to make sure it`s remained at the right amount) Faulty seal in the master cylinder.
With the car turned off, pump the brake pedal four or five times until you get a hard brake pedal. Continue to hold the brake pedal down with moderate pressure and start the vehicle. The brake pedal should drop. If this brake pedal remains hard, there is a problem with the brake booster, such as a ripped diaphragm.
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.
In the pressure method, a pressure pump is attached to the master cylinder, pressurizing the system, and the bleeder valves are opened one at a time until the fluid is clear of air. Specialised pumps may incorporate a method to automatically keep the brake fluid reservoir full during bleeding.
Typical operating pressure is approximately 100–120 psi or 690–830 kPa or 6.9–8.3 bar. A compressed-air-brake system is divided into a supply system and a control system.
The pressure in the master cylinder is close 300 pounds per square inch, equivalent to the same pressure generated in the boiler of an old steam locomotive.
If the ABS system detects that one wheel is slowing down more rapidly than the rest (a symptom of wheel-lock) it automatically reduces the brake pressure on this wheel by opening a pressure release valve in the hydraulic system. ABS also has the ability to build the pressure back up via the hydraulic motor.
The ABS controller knows that such a rapid deceleration of the car is impossible (and in actuality the rapid deceleration means the wheel is about to slip), so it reduces the pressure to that brake until it sees an acceleration, then it increases the pressure until it sees the deceleration again.
This pressure travels from the master cylinder, through the brake line, and acts on the brake caliper and brake rotor. However, if air bubbles are in the brake line, hydraulic pressure is reduced, making your entire braking system less effective and your vehicle more difficult to control.
While running pump the pedal until it is firm. If it holds in the same place it is air in the lines, if it slowly descends to the floor it is the master cylinder.
Let us begin by mentioning that a little brake drag is normal and brake pads and rotors are usually in slight contact. If you were to spin your wheel, the wheel should be able to partly turn on its own.
Loose brake pedals that wobble back and forth are also subject to fail without much other warning. A sound of air or a “whoosh” type noise when you press the brakes is also cause for concern. The brake lines in your car which are activated by the pedal, or the pedal itself, may need attention.
One of the most common reasons for your brakes touching the floor would be an issue with your brake fluid. Your fluid being low or air reaching the brake line will prevent the fluid from flowing properly, resulting in a spongy pedal. A bad brake booster is another common cause for a malfunctioning pedal.
On the air-brake system the driver must pump or use stab braking in an emergency. If the anti-lock brake system fails or malfunctions, the driver must resort to stopping the vehicle by using the normal air-brake method.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
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.
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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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abs light on brake line broke have been replace I bleed brake line but brake pad still go to the floor now wheels lock up
ANSWER : Hello. If the brake pedal is going to the floor then that means that it is not building pressure. If the brake system has been fully bled and there is no air in it then most of the time it is a bad master cylinder or it can be caused by a bad ABS module. If the brake fluid was low and if air got into the system then the only way to properly bleed it is with a scan tool that would allow you to open and close the valves in the ABS unit. Air gets trapped in these easily if the brake fluid gets low. This can also explain why the brakes are locking up. I would usually use my scan tool to bleed the system out first before going any further. I would also scan the brake control module to see what it is reading as a fault. If there is no air in the system and if there is no prominent code then I would replace the master cylinder first. If you want to check out why your brakes are locking up, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose and repair this.
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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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Brake sensor is to sensitive causing brakes to flicker while driving. 2005 Mercury Montego
ANSWER : Hi there – your brake light switch needs a minor adjustment. It is adjusted too "tight" or close to the brake pedal lever, or possibly has failed. Adjusting/replacing it will eliminate this flickering problem. I recommend a brake light isn’t working inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, and give you an accurate assessment of damage and cost estimate for repairs.
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Replaced calipers and brake shoes. Bled the brakes and loose clutch. Get clutch back and loose brake pressure. Why?
ANSWER : Hello. The symptoms you are describing are very unusual. The clutch and brake hydraulic systems on your vehicle are separate, and should function completely independently of each other. The brake master cylinder uses a completely different set of lines than the clutch master cylinder does. I would try carefully bleeding both systems once more, just to be sure that there is no air in either system.
If both are bled properly, I would then move on to making sure that none of the components of either system are leaking. Leaks at the master or slave cylinders, or at any of the calipers or wheel cylinders will cause the systems to lose pressure. If the problem persists, I would then consider the possibility of a defective master cylinder.
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Brake pedal has very little resistance
ANSWER : From what you’ve described, I’d advise you to not drive the vehicle and get the brakes bled out. It’s possible that you still have a brake fluid leak in this case.
I’d suggest having this looked at by a certified technician, like one from YourMechanic, who can diagnose your brake system firsthand and bleed your brake system if necessary. Best of luck.
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I own a 2000 f150 lariat 4 x4. 5.4 l. Started getting a loud grinding noise front passager brakes. Replaced brakes and wheel
ANSWER : Hi there. While using junkyard or used parts (especially brake or suspension parts) is highly discouraged and can cause major damage, it is unlikely that they caused the aluminum wheel to split in half. In most cases, this is caused by hitting a pothole or other obstruction in the road. A glancing blow against a blunt object like a curb can also cause this type of damage. However, if the brakes came apart or a brake component broke, it could in theory cause the same damage. My advice to you is to not drive the vehicle further until you’ve replaced the brakes and wheels with new components for safety.
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