New Brake Caliper Not Releasing – Causes and Fixes

Diagnosing any brake system-related problem can be extremely time-consuming and challenging. And the fact that your safety is on the line makes it that much more anxiety-inducing. Luckily, fixing the problem described in the title is fairly easy since only a couple of things can lead to such circumstances.

The most common cause of a new brake caliper not releasing, in most cases, is a collapsed and deteriorated rubber brake line. Other than that, it could be a defective brake caliper, especially if you bought a remanufactured one instead of a brand-new one. And lastly, it could be a faulty master cylinder.

brake caliper not releasing

What Causes New Brake Calipers Not Releasing

The most common cause of a new brake caliper not releasing is fairly simple, the rubber brake lines. Now, if your old brake caliper has failed because of age, you should definitely replace the rubber hoses, even if it turns out they are not the problem. Rubber hoses disintegrate and can break while driving, leaving you without any braking power. And especially if only one front brake is locking up.

Also, if you have bought remanufactured calipers or you found new ones on eBay on Amazon, you should also focus on the part about defective calipers. But, of course, change those old rubber lines before you do.

Clogged Rubber Brake Lines

In most cases, when a brand-new brake caliper is sticking or the brakes are not releasing all the way, it’s because of a collapsed rubber brake line. Those brake lines have thin rubber linings inside to prevent damage from the abrasive brake fluid. But with age, that lining collapses and stops the brake fluid flow. However, it stops the flow in only one direction.

When you push the brake pedal, the pressure inside the lines is more than high enough to pass through the collapsed hose lining. However, when you release the brakes, the fluid flows in the opposite direction at a much lower pressure making it substantially easier for the rubber lining to stop the flow. Hence, the brake fluid can flow in one direction when you apply the brake but can’t return to release the brake caliper pressure. If only one front brake is locking up, then a bad brake line is the most likely cause.

Defective Brake Caliper

If you are sure the brake lines are good, or you had them replaced recently, then the brake caliper could have some factory defects. And while that’s unlikely if you bought a brand-new OEM caliper, it’s pretty common with remanufactured ones.

The problem with remanufactured calipers is that the caliper piston can seize because they use the wrong grease. And the same thing happens with the caliper slider pins. Again, when you push the brakes, the brake fluid pressure is immensely high, so it can overpower even a seized piston. However, the pressure is nowhere near enough when you release the brakes, so they remain stuck. And if you have replaced two brake calipers and both front brake calipers are not releasing, then the calipers are most likely defective.

Seized Master Cylinder

Lastly, you might be looking at a faulty master cylinder, even though it’s the least likely cause. The master cylinder also has pistons and rubber seals around them. But when those seals begin to break down, the pistons can get stuck, after which the brake master cylinder is not releasing pressure. But in this case, all four brake calipers will stick, which is a dead giveaway that the master cylinder is bad.

What to Do If New Brake Caliper Is Not Releasing

Replacing the old brake lines is extremely simple and cheap, which is why we once more recommend you focus on that first. And if that doesn’t fix anything, all is not lost since the new brake calipers might just need a good cleaning and greasing up. So, stick around as we explain everything you should know about each potential cause.

Replacing Old Brake Lines

The first step in fixing a new brake caliper that’s not releasing is to inspect the rubber brake lines. You can do that by bleeding the brake fluid on the affected caliper, and if the fluid is coming out of the bleed nipple without much pressure, it’s the brake lines.

Luckily, replacing new brake lines is pretty straightforward as long as the metal lines aren’t too rusted out. Also, the rubber brake lines are not too expensive, at least not compared to brake calipers. A set of two rubber brake lines costs between $20 and $40, depending on the length.

Fixing the Defective Brake Caliper

In case the calipers are still sticking after replacing the rubber brake lines, try removing and inspecting the slider pins if your car has them. If the slider pins look dirty and it looks like the grease on them is stuck and hard, then that’s your problem.

To fix that, first, clean the grease off the pins. You can use a steel wire brush and even some light sandpaper, but try with some light degreaser fluid, like WD40. Then, put some waterproof silicone grease on the pins, and you should be good to go. That type of grease is perfect for High-temperature conditions, a brake caliper meets, and it’s a perfect water-repellent that helps reduce oxidization.

Unfortunately, if that doesn’t help either, or the slider pins look good, you have most likely bought a defective brake caliper. In that case, avoid trying to fix it and buy a new one.

Also, even remanufactured calipers often have some type of warranty, or at least the shop where you bought them has a return policy. Whatever the case, buy a new brake caliper, preferably an OEM one, or test your luck with another remanufactured unit.

Replacing the Master Cylinder

If all of the above looks good, or if all four of the brake calipers are sticking or not returning, replacing the master cylinder is your last resort. But before you do, have the vehicle inspected by a professional because replacing the master cylinder isn’t a DIY-friendly job; it’s also consuming, and the master cylinder itself can be pretty expensive.

And if it turns out you need one, a brand new master cylinder will set you back anywhere between $130 and $300. However, a new master cylinder can be as much as $800-$1,000 for newer premium models. As for labor costs, according to, they can be between $150 and $300. That brings the total cost to roughly $400, with $280 on the low end and $1,300 on the high end.

one front brake locking up


Q: Why is my brand-new brake caliper sticking?

Your brand-new brake calipers are sticking, most likely because of old and clogged rubber brake lines. On the other hand, it could be a defective brake caliper, dirty sliding pins, or a faulty master cylinder.

Q: How do you unstick a new brake caliper?

The best way to unstick a new brake caliper is to use a caliper piston retracting tool after you lubricate the piston with some WD40. Also, retract the piston intermittently to avoid causing any damage. Other than that, try to remove the slider pins in case you can’t remove the brake caliper to retract the piston.

Q: Is it ok to drive with a sticking caliper?

No, it’s not ok to drive with a sticking caliper, even though the car may not present any symptoms. A sticking caliper will quickly overheat the brakes and potentially lock them up while driving. Not only will that leave you stranded, but it’s a perfect recipe for a major accident.

Q: Can you spray WD40 on brake calipers?

Yes, you can spray WD40 on brake calipers, caliper pistons, sliding pins, and even brake pads and rotors. WD40 is nothing more than a penetrator and a degreaser which is nowhere near abrasive enough to cause any damage to metal components.

Q: Why won’t my brake caliper compress?

If your brake calipers won’t compress, the most likely culprit are rusty caliper pistons or sliding pins. That usually happens because of broken caliper pistons or sliding pin rubber boots, which let moisture inside. Also, if the caliper is working properly, you can check the rubber brake lines and the master cylinder.

Final Words

At the end of the day, from everything that I have found and from my personal experience, the most likely reason, and one you should check, regardless of what’s causing the new caliper to stick, are the rubber brake lines. Rubber brake lines can crack while driving, leaving you without brakes; plus, if the old brake caliper was due for a replacement, chances are the rubber hoses are as well.

Other than that, a brand new brake caliper that’s sticking can be because of low quality, or you bought a remanufactured one, all of which are prone to failure. And lastly, it could be a seizing master cylinder, but that should be the last thing you check.


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