Why did my garage door make a loud bang or gunshot noise?

You were sitting in the living room or lying in bed when the garage shook with a sound like a gunshot or a car backfiring. Nothing crashed. No one rang the doorbell. You walked out to the garage and everything looks normal except the door will not open. Here is what happened and what to do next.

What makes a garage door sound like a gunshot?

The most common cause by a large margin is a broken torsion spring. A torsion spring sits on a steel shaft mounted horizontally above the garage door. It is wound under several hundred pounds of torque to provide the counterbalance that makes a heavy door easy to lift. When a torsion spring breaks, it releases all of that stored energy in a fraction of a second. The spring snaps apart and the two halves spin rapidly on the shaft. The impact of the break and the vibration through the steel hardware creates a sound that homeowners routinely describe as a gunshot, a car backfiring, or a firecracker going off inside the garage.

The sound is startling because the energy release is nearly instantaneous and the metal components of the garage door frame act like a resonance chamber, amplifying the impact. It is also completely normal - springs have a finite cycle life and break when they reach the end of it.

Less common causes of a sudden loud bang include a lift cable snapping under tension, a panel hinge failing and letting a panel corner drop sharply, or a trolley carriage releasing under load. Each of these has a different sound quality, but they are all loud enough to alarm homeowners.

How to confirm the spring broke

Walk into the garage and look up at the horizontal shaft above the door. On most residential doors you will see one or two torsion springs on this shaft. A broken spring has a visible gap in the coils, usually near the center of the spring. The two ends of the spring will be separated by an inch or more.

On some double-car doors, there are two springs side by side on the shaft. If only one broke, the gap is in just one spring. Both should still be replaced at the same service visit because if one broke, the other is at a similar wear stage and will likely break soon.

If the springs look intact but the door still will not open, the problem may be a snapped cable, a stripped opener gear, or a trolley that came disconnected. The repair is different but the immediate advice is the same: do not force the door.

Cause	Sound	Visual sign	Door behavior
Torsion spring break	Sharp bang, single crack	Gap in spring coils above door	Door very heavy, won't open
Cable snap	Sharp crack or pop	Loose wire near bottom track	Door hangs lopsided
Opener gear strip	Grinding, then silence	Motor runs, door stays still	Opener motor hums
Panel hinge failure	Loud clank	Panel corner dropped	Door binds in track

What to do right now and is it safe to fix yourself?

Do not press the opener button more than once to test it. If the spring broke, the opener will try to lift a 150 to 300 pound door without the counterbalance the spring normally provides. This puts extreme stress on the opener motor, can strip the drive gear, and may damage the trolley assembly. One test press tells you the door is not working. Stop there.

Unplug the opener from the ceiling outlet so no one else in the household can accidentally trigger it.

If you need to use the door before it is repaired, pull the red emergency release cord to disconnect the trolley and try to manually lift the door. A door with a broken spring is extremely heavy because you are lifting the full weight without any spring assist. On a 16 by 7 foot door, that can be 200 pounds or more. Most people cannot lift this safely alone, and doing so risks injury and damage to the opener and trolley. If a car is trapped and you genuinely need it, call for emergency service rather than forcing the door by hand.

Spring replacement is the most hazardous DIY repair in the garage door category. The Consumer Product Safety Commission identifies garage door springs as a leading source of serious garage door injuries in the home. A loaded torsion spring stores enough energy to cause severe lacerations, broken bones, or worse if it releases suddenly while being handled.

Proper replacement requires steel winding bars that fit the winding cone holes exactly. Screwdrivers, ratchet handles, and makeshift tools are not acceptable substitutes. They can slip out of the cone under load, sending the bar flying and allowing the spring to spin uncontrolled. A professional technician completes this work using the correct bars and a sequence of controlled quarter-turn increments, stopping after each turn to confirm the spring is behaving as expected.

The cost of professional spring replacement typically runs $150 to $350 for a standard single torsion spring and $250 to $450 for two springs. This is a small cost compared to an emergency room visit or permanent injury. Most professional garage door companies carry the most common spring sizes on their trucks and can complete the repair in a single visit the same day you call.

What happens if you ignore a broken spring?

A door with a broken torsion spring will not stay in the service it was designed for. Even if you can lift it manually, the full weight falls on the opener motor every time it is used. Openers are designed to assist a balanced door, not to lift a door unassisted. Running the opener against a broken spring shortens motor life, can strip the gear, and usually results in the opener failing within a short time.

The door is also prone to dropping suddenly when in the open position. Torsion springs hold the door up when it is open. Without that holding force, a door in the open position is relying solely on the opener trolley and any friction in the tracks. This is not a stable situation, especially in an older opener.

Beyond the opener damage, there is a safety consideration for anyone who walks under an open door. A door that drops unexpectedly causes injury. The CPSC has documented garage door injuries from exactly this situation.

How quickly can this be repaired?

Spring replacement is one of the most common garage door repairs and most professional companies carry the common spring sizes on their trucks. Same-day service is standard at G Brothers Garage Doors for broken springs in the Denver metro and across the Front Range. The repair itself takes 45 to 90 minutes for a trained technician, and the door is back in normal service immediately after.

When scheduling, mention whether the door has one or two springs so the technician can bring the right inventory. If your door is a standard residential sectional door with a 7 or 8 foot height, the springs are almost certainly a common size that will be on the truck.

Call G Brothers for a free estimate and same-day scheduling. We serve Denver, Aurora, Lakewood, Englewood, Littleton, Parker, Castle Rock, Centennial, and the surrounding Front Range communities.