Coil springs and lift supports
A coil spring holds the vehicle up. A lift support holds a hood, a hatch, or a trunk lid open. The names get swapped in search boxes. The parts do not swap on the car.
Coil springs
A suspension coil spring is a steel helix that carries the corner of the vehicle. The damper, a shock or a strut, controls the motion. The spring sets ride height. Spring rate is how much force it takes to compress the spring a given distance. Free length is the spring off the car. Installed height is what you see with the car on its wheels. Two springs can share a shape and differ in rate, so a spring that bolts in can still sit the car at the wrong height.
Springs sag with age. The car sits lower than it used to, sometimes more on one side, and a tire can tuck into the fender. A broken coil is a different failure. You may hear a clunk, see a gap in the helix, or find one corner suddenly low. A broken spring can let a damper or a brake line take a load it was not meant to take. Do not keep driving on it, especially if the break is near a tire.
Replace coil springs in pairs on an axle. A new spring next to a sagged one leaves the car tilted. Match the spring to the engine, the body, and any load package. A heavy-duty or towing spring is stiffer or taller because the vehicle was built to carry more. A base spring under a vehicle that still carries that equipment will sag again. Read the fitment line the same way you would for a strut or shock.
On a strut suspension the spring is captured on the strut. Replacing it means compressing the spring and moving it, which is the dangerous step. A complete strut assembly arrives with the spring already installed, which is how most owners avoid a spring compressor. On a control-arm or solid-axle suspension, the spring sits in a pocket and can leave it suddenly if the arm drops too far. Follow the service sequence, including any mark that indexes the spring so it does not rub the tower.
Lift supports
Lift supports are the gas struts that hold a hood, a rear hatch, a trunk lid, or sometimes a rear window. A rod slides in a charged cylinder. When the panel is open, the pressure inside pushes the rod out and holds the weight. They are sometimes called gas struts, prop rods, or lift cylinders. They are not suspension struts. Ordering a “strut” from the suspension category will not hold your hood.
A failing support shows itself in the panel. The hood will not stay up, especially when cold. A hatch falls toward closed instead of staying at the top of its travel. Oil on the rod means the seal has leaked and the gas charge is leaving with it. A bent rod, often from closing the panel on a support that was not aligned, will stick or leak next. One strong support can hide a dead partner until the lid drops without warning.
Replace lift supports in pairs. The old one left in place is the same age and will not share the load evenly. Match the extended length, the compressed length, the end fittings, and the force listed for that panel. A support that is the wrong length can bend hinges. Ends are usually a ball socket on a stud, or an eye with a bolt. Buy the same arrangement. Left and right can differ.
Replacing a lift support
Before you remove either support, prop the panel with a second person or a prop rod that cannot slip. Do not trust the remaining support to hold a hood while your head is under it. Many sockets release with a small clip or a screwdriver at the edge of the socket. Pry the clip only far enough to slide the socket off the ball. The socket can pop free and the panel can drop in the same moment if it is not held.
Note which end is up. Some supports are meant to be installed rod-down or rod-up so the seal stays lubricated. Follow the note on the box. Clip the sockets on until they seat, remove the temporary prop, and test the panel. It should stay open without creeping down. If it creeps, check that you received the support for that panel, not a shorter one meant for a different lid.
Do not try to recharge a leaked support, and do not clamp the rod in a vise. The rod is the sealing surface. A scratch ruins the new seal if you reuse a rod, which is why the whole support is the replacement part.
What not to confuse
Search results mix these parts because the word strut appears in both. Use the product line. Suspension coil springs and strut assemblies live with the suspension parts. Hood, hatch, and trunk supports live with body hardware. On PartIndex, pick the vehicle first so the line you open is already limited to that car, then read the part name. A coil spring listing will talk about ride height and axle. A lift support listing will name the panel.
Air springs and air shocks are another neighbor. They hold the vehicle up with air pressure and a compressor. They are not charged gas props, and they are not a plain coil. If the vehicle sits on air from the factory, a coil-spring catalog entry for a different suspension will not bolt into that system. Confirm the suspension type before you compare prices.
A hood or hatch that falls can injure anyone under it. Support the panel before you remove a lift support, and keep hands clear of the hinge path. A coil spring under compression can leave its pocket with enough force to cause a serious injury. Do not cut, heat, or clamp a spring with improvised tools. If you do not have the compressor and the procedure, use a loaded strut assembly or have a shop do the spring work. A broken coil can shift the car on a jack. Use stands, and do not crawl under the vehicle until it is supported.
After either repair, look once more at ride height or at the open panel. A corner that still sits low needs another look at the spring seat, not another mile of driving. A hatch that stays up on its own is the whole test of a lift support.