My brakes are sticking

When you press the brake pedal and then release it, the pedal should immediately release and release pressure from the master cylinder which means the calipers will "spring" back and push the fluid back to the reservoir. If the calipers are not releasing then it is normally a caliper but if you have both front calipers doing it then more than likely it is something they have in common. So if they slowly release then that is because the fluid is being restricted from returning. This happens when the brake booster push rod is adjusted out too far which does no allow the brake master to return fully holding the brakes on. To confirm the issue loosen the brake master mounting bolts 3 turns to see if the car starts to roll again, if so remove the master and adjust the booster push rod inward.

First, press the brake pedal and watch to see if it is releasing or returning to the proper position or is it remaining low.

Unless the pedal is getting stuck on something (unlikely) then the most likely cause is the brake booster. Basically there is to be vacuum on both sides of the diaphragm but the air valve between the two sides sticks and holds pressure which doesn't allow the spring in the diaphragm to return the pedal to return. This holds the fluid in the calipers and doesn't allow the brakes to release.

Have you checked the rear brakes to see if they are holding as well? If it is just the front then the master cylinder is most likely the issue.

Let me know what you find and we can go from there. Thanks

Hi guys. Please let me add a few comments of value, then I'll go sit in my corner.

If someone added brake fluid in between, it is going to run over and make a huge mess. That brake fluid eats paint too. If there is no obvious leak, low brake fluid level is an indication a brake system inspection is in order as part of regular maintenance, and expect to find the front disc brake pads need to be replaced. I'm sure some of these owners will share their complaint with anyone who will listen, and some of them will top off their own brake fluid. You have to wonder how many of them will unwittingly contaminate their brake systems, and if a problem develops, it is likely to become one of those "ever since" issues. "Ever since" that shop worked on my car, it has had this problem. The best we can do to prevent this is education.

Sounds great. Let us know. Thanks

We need to find out which wheels are doing it. I would suggest driving the vehicle to where it is acting up and then lift the vehicle and spin the wheels to see which one is grabbing. At that point we can test that leg of the system.

Let me know what questions you have and we can figure it out. Thanks

Okay. That could be an issue with the proportioning valve. Basically this determines how much pressure to send to the front and rear brakes. It tries to keep the front or rear from locking up but it may be sending too much pressure to the front causing them to drag.

Keep us posted on what they find. Thanks.

Dandy. Happy to hear you solved it.

Can you tell if it's front or rear OR all 4?

As the ESC light came on it should have stored a code but you need a factory grade scan tool to read them, the free scans only cover the engine codes. If you can get the codes it would make it easier. Without them the below are the likely culprits.

The description sounds like you have a sticking caliper piston. That could be due to uneven pad wear that twists the caliper. Checking requires removal of the wheel/tire and visual inspection of the pads and rotors to see if they are worn uneven.

It could also be a failing flexible brake line. They can fail inside and act like a one way valve. You apply the brakes and the fluid either cannot return or returns very slowly.
These can be hard to find if it only happens once in a while because they will look fine on the outside. Sometimes you can find them if you jack up the vehicle and stomp the brake and have someone immediately try to spin the wheel by hand as soon as your foot is off the pedal. If the wheel is hard to turn and slowly gets easier I would suspect the line.

If it's all 4 I would look at the master cylinder and the ABS module, after getting the codes.

Brake fluid is trapped and can't get back to the master cylinder. When it happens again, loosen the mounting bolts for the master cylinder. If the brakes release, check the push rod to see if it's over-adjusted, or if the brake light switch is misadjusted and holding the brake pedal down. If they don't release, open the bleeder screws at the front calipers. If the brakes release there, check the rubber flex hoses.

Why did you replace the master cylinder? Any chance the fluid is contaminated with petroleum product?

The first thing to check is the rubber bladder seal under the reservoir cap. If it's blown up and mushy, there' a petroleum-based contaminant in the brake fluid. The only proper repair for that is to replace every part in the hydraulic system that contains rubber parts that contacts the brake fluid, and all steel lines must be flushed and dried.

At 52,000 miles and six years old, it's very unlikely the master cylinder failed on its own. If it failed due to fluid contamination, that contamination will leach back out of other seals and hoses and recontaminate the new master cylinder. That typically takes a few weeks to a couple of months.

The way to prove or disprove this is to loosen the steel lines right at the master cylinder while the brakes are locked up. If they release, fluid contamination is the chief suspect. The misadjusted push rod or brake light switch that I mentioned previously wouldn't be okay for three months, then suddenly start causing a problem.