Brakes won’t let go after changeing main brake cylinder.

OK, I changed the main cylinder (new part) because it went straight to the floor without brake power. Workshop said it was wrong fluid on the system. I changed all brake fluid and replaced with Dot +4.

After changing the cylinder the brakes locked. They do brake normally but does not let completly go, and my disks get hot. It is not impossible to drive, but the car struggles in 5th gear, and wont roll freely in gently downhill.
However, the problem is solved by pulling the pedal gently outwards and by doing so after each braking it is possible to drive. This happends on all 4 wheels.

My tro

Experienced mechanics share their insights in answering this question :
Rule out obvious causes such as sticking calipers. If you are positive that the caliper pistons are free and the pins in the torque plate are free as well, measure the brake line pressure at each wheel to determine both if the pressures are correct (and proportioning valve is working) and if pressure releases. If pressure is not releasing, see if failure to release is in one or both circuits (the brake system is sectionalized for safety). If the problem is global, the master cylinder is stuck. If this does not resolve it, request a brake system diagnostic – pressure testing and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

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.
If your car has rear drum brakes and the brake pedal goes to the floor, the rear brake shoes could be out of alignment. Sediment. Sometimes when new brake pads are installed, sediment can inadvertently be pushed back into the hydraulic system. This sediment can damage the master cylinder.
When your pedal is sticking and not returning, it`s most likely fixable with the 2 suggestions given above: Clean and lube the pedal pivot. Replace the master cylinder.
Brake Booster Push Rod Length

Similar to the above scenario, the pin between the brake booster and the master cylinder can be too long. This will not allow the master cylinder to release completely. To correct this problem, it is necessary to determine the distance between the push rod and the piston.

The parking brake cable may be stretched out, corroded, or damaged in another way. A damaged cable may prevent the brake from releasing. If you suspect that the cable is causing your parking brake to stick, you can visually inspect it.
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.
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.
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.
If it malfunctions, the cylinder will not distribute pressure properly, and the pedal will be affected. When you continue using your car will a bad cylinder, it will wear out and start leaking. The pedal will also feel spongy, mushy, and may sink far down when pressed.
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.
Low Brake Fluid: If your brake fluid is low (and it`s not due to brake pad wear), then the system will be unable to create enough pressure for normal operation and you may have to pump the pedal.
Step 5: Pump Your Brakes

Essentially you`re priming the brakes by creating hydraulic pressure inside the brake lines with the fresh fluid. You`ll need to pump your brakes about 30 times and stop when you feel the pedal engage. Well, now you know the proper and safe way to add brake fluid.

Most brake pad compounds will take up to 300-400 miles to fully develop an even film transfer onto the rotors.
Making sure the vehicle is in neutral or park, pump the brakes 15 to 20 times to make sure the pad is seated properly. Top off brake fluid levels or follow bleeding of brakes section to flush out old fluid and replace with new fluid. Test your new brake pads.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Brakes won’t let go after changeing main brake cylinder.
ANSWER : Rule out obvious causes such as sticking calipers. If you are positive that the caliper pistons are free and the pins in the torque plate are free as well, measure the brake line pressure at each wheel to determine both if the pressures are correct (and proportioning valve is working) and if pressure releases. If pressure is not releasing, see if failure to release is in one or both circuits (the brake system is sectionalized for safety). If the problem is global, the master cylinder is stuck. If this does not resolve it, request a brake system diagnostic – pressure testing and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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.

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.

My car won’t go past 35mph
ANSWER : Hi there. From the description you provided, your vehicle has problems with the transmission again. You stated it will not shift into 3rd gear again, like before the transmission was rebuilt. If the transmission is again the problem, it should be covered under warranty. It could be a faulty shift solenoid. The shift indicator not reading properly could be a faulty transmission position sensor. If this is an overall lack of performance issue, according to your last statement, then possibly you have a restriction in the exhaust system. I recommend having your vehicle’s problems inspected and diagnosed by a certified technician from YourMechanic.

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.

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.

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.