How do I tell the difference between a break line popping and a master cylinder going bad while my foot was on the brake?

i was starting the car and the steering wheel locked up and i pushed it to unlock the wheel and when i was starting the car the brake pedal went to the floor and it was very mushy the rest of the way home i had to push it almsot all the way to the floor to stop

My car has 250000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
You may have an internal piston seal leaking inside the master cylinder or a leak somewhere in the brake system. You would know the difference by looking in the master cylinder to see if the fluid is real low or empty. If it is then the master cylinder most likely is not the problem but a leak in the brake system somewhere is. I recommend having the brakes checked to see if you see any evidence of a leak under the vehicle if the fluid is gone out of the master cylinder. If the front brake calipers leak you will see fluid on back side of a wheel. If it is a brake line leaking then it may be due to rusted through lines and may need multiple line repairs to fix the rusted lines. Have a brake safety inspection to check the entire system integrity.

How to Identify and Fix Common car Problems ?

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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.
A failed master cylinder can cause a low or spongy brake pedal but generally does not make any noises. If however you hear a loud hissing sound when the brakes are applied, the power/vacuum brake booster may have a vacuum leak.
Common Signs of a Bad Brake Booster

Signs can include: The brake pedal is harder to push than normal. Since the brake booster operates with vacuum, the degree to which the brakes are more difficult to apply can vary.

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.
On the mastercylinder what line is for the front brakes and what is for the back. Typically the front line goes to the rear wheels and the rear line goes to the front.
Internal master cylinder leaks can be pinpointed by removing the brake lines and inserting metal plugs into the master cylinder outlets or onto the metal brake lines connected to the brake hoses. If the brake pedal continues to sink to the floor, the leakage is in the cylinder itself.
The most common way that brake lines fail is that they begin to leak. They are usually made of steel and capable of withstanding pressures. However, they can sometimes become worn or damaged as the vehicle is driven and are susceptible to leaks.
Your callipers might stick rather than come off smoothly because fluid can`t move back down the hose to release its pressure. If your callipers stick, then you`ll notice that something is wrong as you drive. For example, your car might veer to one side. You may hear squealing noises when you brake.
How long will brake lines generally last? Most new cars and trucks come with stainless steel brake lines that are expected to last seven to fifteen years before requiring replacement. It is one of the most durable parts of your vehicle and is considered a lifetime part.
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.
Turn the engine off, then repeatedly press the brake pedal slowly. When you pump it the first time the pedal should be very `low`— meaning not much pressure resistance. As you pump the pedal, the pressure should become firmer, which will indicate that the brake booster is not leaking.
When the brake booster is failing it can draw excess vacuum from the engine. This occurs when the diaphragm inside the brake booster fails and allows air to bypass the seal. The brakes are then pressed, the engine feels like it will stall, and the idle can drop.
If your car has independent suspension, you`ll find separate brake hoses for your front and rear brake systems. But if you have a live axle, you`ll likely have one hose connecting from the master cylinder to the rear brake.
Increased Durability

The most obvious advantage of copper-nickel brake lines is that they are much more durable than traditional steel or stainless steel brake lines. Copper nickel is much less likely to oxidize or corrode, making it ideal for use in dirty or harsh environments.

A copper brake line is the best quality brake lines you can buy for a longer-lasting life on any vehicle, farm vehicle and industrial vehicles alike. Copper tubing is easy to replace because it is a pliable and bendable product that can make bends and turns without breaking.
The ABS modulator is the hydraulic assembly in vehicles that use the anti-lock braking system (ABS) to optimize the brake pressure. A damaged modulator may lead to malfunctioning of the brake valve resulting in spongy brakes.
Air in the brake lines can also cause a hard brake pedal. Air in the brake lines will prevent the brake fluid from flowing smoothly, leading to a loss of hydraulic pressure and a hard brake pedal.
When a line blows, only one circuit is damaged and the other circuit still functions. Pumping the pedal can build up pressure in the lines and give you a little bit more braking action. While it won`t restore full braking capability, it can give you enough response to control the car and help you stop safely.
A: Brake fluid leaks are often caused by a worn seal in the master cylinder, caliper, or wheel cylinder. If you suspect your car is leaking brake fluid, call a tow truck to take your vehicle to a service provider for a brake fluid inspection. Brake fluid leaks can lead to total brake system failure.
Once brake lines become damaged, moisture has the ability to get into the braking system. This can limit your brakes overall effectiveness or cause them to fail completely!
There are two basic types of flares used on OEM automotive brake systems throughout the world. The SAE/double (inverted/45degree) flare and the DIN/ISO bubble flare. We will refer to them as SAE or DIN flare.
The benefit of braided lines is the durability; over time rubber brake lines become soft so, as they expand under pressure, you lose some of the force that`s applied to the brake pistons; your brakes end up feeling a little spongy and slower to respond.
Brake lines connect the actuation device, such as the brake master cylinder, to the hydraulic components of the wheel brake. Brake hoses are used as flexible connecting lines in all moving areas between the body and chassis.
If you find rust or suspect rust is eating at the line, or even if you live in the “rust belt” states where lots of road salt is used, pop the lines out of their body clips and look carefully for corrosion. A little surface rust is alright, but if there is notable deep pitting it`s time to replace your brake line!

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

How do I tell the difference between a break line popping and a master cylinder going bad while my foot was on the brake?
ANSWER : You may have an internal piston seal leaking inside the master cylinder or a leak somewhere in the brake system. You would know the difference by looking in the master cylinder to see if the fluid is real low or empty. If it is then the master cylinder most likely is not the problem but a leak in the brake system somewhere is. I recommend having the brakes checked to see if you see any evidence of a leak under the vehicle if the fluid is gone out of the master cylinder. If the front brake calipers leak you will see fluid on back side of a wheel. If it is a brake line leaking then it may be due to rusted through lines and may need multiple line repairs to fix the rusted lines. Have a brake safety inspection to check the entire system integrity.

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.

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.

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.

Could the brake servo booster that the master cylinder attaches to cause the brake pedal’s excessive travel?
ANSWER : Hi there. Typically, when a brake booster fails, the result is a hard to push brake pedal. The pressure release you hear is engine vacuum and may be normal considering, the brake pedal travels to the floor. With no apparent leak(s) in the hydraulic braking system, the master cylinder internally bypassing is the most common failure. Having replaced the master cylinder, this leads me to believe, there may be air trapped and a flush may resolve this concern. Assuming, the vehicle is equipped with ABS (anti-lock brake system). The ABS hydraulic modulator assembly may be internally bypassing. I recommend having your vehicle’s brake pedal issue diagnosed and repaired by a certified technician, such as one from YourMechanic.

Replaced master cylinder and brakes still going to the floor and not working. Bed both master cylinders and each wheel.
ANSWER : Hi, thanks for writing in. At first it sounds like you may still have air in the system. The other option is that you may have a leak somewhere. Try to bleed the master cylinder and the lines again. The new master cylinder must be bench bled off of the vehicle exactly as the instructions say. The other problem could be a leak on the system. You should check for drips, puddles forming, or other signs of leaking brake fluid. Worst case scenario, the replacement master cylinder may have come to you faulty in the first place. This is rare but can happen, especially when it comes to remanufactured master cylinders. New ones typically don’t have issues. If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make or suggest any repairs as needed.

I just replaced my brake master cylinder and the brakes still feel soft. What do I need to do after I replace the master cylinder
ANSWER : From what you’ve described you will have to bleed your brakes. Also, I believe you may have a leak in one of the lines. You may want to use a wrench and tighten the lines a little more. If you’re unable to fix this yourself, consider YourMechanic, as one of our mobile technicians can come to your home to bleed your brakes, diagnose the Check Engine Light, and help you make the appropriate repairs to your car.

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.