Signs Your Car Gas Struts Are Failing (And What to Do About It)

Author : Mason Creed | Published On : 12 Jun 2026

Gas struts work so reliably for so long that most drivers never think about them — until one fails. The problem is that failure rarely happens suddenly. It builds gradually over months or years, and the early warning signs are easy to dismiss as minor inconveniences rather than maintenance signals.

By the time a gas strut fails completely, you're already dealing with a safety issue. A bonnet, boot lid, or tailgate that drops without warning can cause injury, damage surrounding components, and leave you in an awkward situation roadside.

This guide covers every vehicle opening where gas struts are commonly fitted, the specific failure signs for each, and how to assess whether replacement is overdue.

In this article:

• Where gas struts are fitted on vehicles
• How gas struts fail
• Signs your bonnet struts are failing
• Signs your boot lid struts are failing
• Signs your tailgate or hatch struts are failing
• Signs your canopy or hard lid struts are failing
• Signs across all applications — quick reference
• How to do a basic strut check yourself
• When to replace versus monitor
• FAQs

Where Gas Struts Are Fitted on Vehicles

Gas struts are used on any panel or lid that needs to open to a fixed position and stay there without manual support. On a typical passenger vehicle, that includes:

• Bonnet — one or two struts depending on the vehicle
• Boot lid — on sedans and coupes
• Tailgate — on wagons, hatchbacks, and SUVs
• Rear glass — the independent rear window on some wagons and 4WDs
• Ute canopy lids — side-opening panels and rear lids on aftermarket canopies
• Hard tonneau covers — some tilt-and-fold designs use gas struts
• Glovebox lids — some vehicles use small struts to dampen the glovebox drop

Each application uses a strut calibrated for the specific weight, opening angle, and mounting geometry of that panel. Failure signs are similar across all of them, but the safety implications and urgency differ.

How Gas Struts Fail

All car bonnet gas struts use the same basic principle: compressed nitrogen gas inside a sealed cylinder pushes against a piston attached to a rod. The pressure in that cylinder is what provides lifting force and holds a panel open.

Failure almost always comes down to one of three causes:

 

Seal degradation is the most common. The internal O-rings and seals that keep the nitrogen gas contained degrade over time through heat cycling, UV exposure, and normal mechanical wear. As the seal weakens, gas pressure slowly drops — which is why strut failure typically presents as a gradual softening of hold rather than a sudden collapse.

Piston rod corrosion is the second most common cause, particularly in coastal environments and on older vehicles. The rod surface must be smooth and clean to slide through the seal without scoring it. Rust, pitting, or grit on the rod damages the seal from the inside on every cycle, dramatically accelerating pressure loss.

Physical damage — a bent body, cracked end fitting, or damaged mounting point — can cause binding or detachment, producing either erratic behaviour or sudden complete failure.

Understanding this helps with early detection: you're looking for the gradual symptoms of pressure loss before they become the abrupt symptom of a panel that won't stay open.

Signs Your Bonnet Struts Are Failing

The bonnet is the highest-risk gas strut application on most vehicles. It opens over the engine bay — an area where you're likely to have your head, hands, or both during a check or repair.

The bonnet drifts down slowly when open. This is the clearest sign of pressure loss. Open the bonnet fully, release it, and step back. A healthy strut holds the bonnet firmly at full extension. A failing strut allows a slow, steady downward drift. If it drifts at all, the struts need replacing.

The bonnet only opens to a partial angle. A strut with some remaining pressure may prop the bonnet partway open — enough to peer in, not enough to work safely. This is a mid-failure state. Replacement is close.

The bonnet feels heavier to lift. New struts actively assist the lift. As pressure drops, that assistance diminishes. If the bonnet feels noticeably heavier to raise than it used to, the struts are weakening even if they still hold open.

You can feel or hear the strut compressing differently. Push the bonnet down 15cm and release it. A healthy strut pushes back with firm, consistent resistance. A soft, spongy feel, or a hissing sound, signals internal pressure loss or seal failure.

Oil residue or moisture around the strut body. Some struts use oil as an internal damping medium. If the seal fails, this oil can seep out and appear as a dark stain or wet patch on the outer body near the piston rod.

Corrosion on the chrome piston rod. The rod is the part that extends from the cylinder — typically shiny and smooth on a functional strut. Any rust, scoring, or brown discolouration on the rod indicates the internal seal is being damaged on every cycle.

Signs Your Boot Lid Struts Are Failing

Boot lid struts fail in the same mechanical ways as bonnet struts but tend to get noticed later because drivers load the boot with their hands, naturally catching or holding the lid.

The boot lid drops when you release it. On a vehicle with healthy struts, the boot lid stays open at full extension without assistance. If it begins to drop — even slowly — the struts have lost holding force.

The boot won't open fully under its own lift. If you release the boot latch and need to manually push the lid up to full extension, the struts are no longer providing adequate lift assistance. This is an early failure sign that's easy to miss because the panel still holds once you manually push it open.

The boot falls quickly when pushed down to close. Healthy struts provide controlled, damped resistance when you push the lid closed. If the lid drops away quickly once you've pushed it past the balance point, the damping function has been lost.

The boot lid sits unevenly. If one strut is further along in failure than the other — common on high-use vehicles — the lid may sit at a slight angle when open, with one side lower than the other. This indicates the struts are at different stages of failure and both should be replaced.

Signs Your Tailgate or Hatch Struts Are Failing

Tailgates and hatches on wagons, SUVs, and hatchbacks are often the heaviest gas-strut-operated panels on the vehicle, and in many cases are opened multiple times daily. High-use applications wear struts faster.

The tailgate drops when released mid-travel. Unlike a bonnet or boot that stays open at a fixed angle, some tailgates are designed to hold at any position in their travel range. If the tailgate drops when you release it partway, the struts have lost pressure.

You need to physically hold the tailgate while loading. This is the most commonly reported sign of tailgate strut failure. If you've started holding the tailgate with one hand while loading with the other — or asking someone to hold it — the struts are already functionally failed.

The tailgate slams or closes faster than expected. Struts don't just hold panels open — they control the rate of travel in both directions. A tailgate that drops faster than normal when closing, or that requires significant effort to hold back, has lost its damping function.

Squealing, grinding, or sticking during operation. These mechanical symptoms suggest corrosion or physical damage to the strut body or piston rod rather than pressure loss alone. They can indicate the strut is binding in its travel, which puts additional stress on the mounting points and surrounding bodywork.

The rear glass opens but the tailgate doesn't assist. On vehicles where the rear glass opens independently from the tailgate, it's possible for the tailgate struts to fail while the glass struts remain functional. Check each independently — they are separate components.

Signs Your Canopy or Hard Lid Struts Are Failing

Ute canopies and hard lids are particularly demanding on heavy duty gas struts. They're exposed to full weather, often used in working environments with dust and vibration, and in some cases are opened dozens of times per day.

The side panels won't stay open while you're accessing the tray. A canopy panel that slowly descends while you're leaning in to retrieve gear is both frustrating and dangerous. Failing struts are the cause in the majority of cases.

The rear door needs to be propped manually. If you've started using a piece of timber, a tie-down strap, or the handle to prop the rear canopy door open, the struts have already failed. This is a workaround, not a solution.

The panels open with a jolt rather than a smooth lift. When a strut has been over-pressured or incorrectly specified — sometimes the case on aftermarket canopies where struts have been replaced with non-OEM parts — the panel can fly open aggressively rather than lifting smoothly. This is also a sign that the wrong strut specification has been used.

Visible corrosion or dirt contamination around the piston rod. Canopy struts in working environments accumulate dust, mud, and moisture. If the rod surface is contaminated and the strut is still cycling, the internal seal is being worn on every open-close cycle. Clean the rod regularly and inspect for scoring.

Signs Across All Applications — Quick Reference

SignApplicationUrgencyPanel drifts down slowly when openAllReplace soonPanel won't hold open at allAllReplace immediatelyPanel feels heavier to liftAllStruts weakening — inspectSoft or spongy resistance when pushing downAllPressure loss — replace soonOil residue or staining on strut bodyAllSeal failed — replace nowCorrosion on chrome piston rodAllReplace immediatelyPanel sits at uneven angleBoot, tailgateBoth struts failing — replace pairSquealing or grinding during travelAllPhysical damage — replace nowPanel drops faster than normal when closingBoot, tailgate, canopyDamping lost — replace soonUsing a prop rod or manual supportAllAlready failed — replace now

How to Do a Basic Strut Check Yourself

A functional check takes less than five minutes per opening and requires no tools.

Step 1 — Open and release. 

Open the panel fully and release it without supporting it. Watch for any downward drift. Healthy struts show no movement. Any drift, however slow, is a fail.

Step 2 — Push down and release.

 Push the panel down approximately 15cm from full open and release. It should spring back firmly and consistently to full extension. A soft, hesitant, or incomplete return indicates pressure loss.

Step 3 — Inspect the rod.

 Look at the chrome piston rod — the section that extends from the cylinder body. It should be clean, smooth, and uniformly shiny. Rust, scoring, oil staining, or contamination means the internal seal is compromised.

Step 4 — Check the mountings.

 Inspect where each end of the strut clips or bolts to the vehicle. Look for cracked ball sockets, loose or corroded mounting hardware, or any play in the fittings. A secure strut on a loose mount behaves like a failing strut.

Step 5 — Test when hot.

 Do the same checks after the vehicle has been sitting in the sun for an hour. Heat temporarily boosts gas pressure, masking borderline struts in cool conditions. A strut that holds fine in the morning but sags in the afternoon heat is already on its way out.

When to Replace Versus Monitor

Not every early warning sign demands immediate replacement — but some do. Use this as a guide:

Replace immediately:

• Any panel that will not hold open without support
• Visible corrosion on the piston rod
• Oil or fluid weeping from the strut body
• Cracked or broken end fittings or mounting hardware
• Any strut on a bonnet where you regularly work with your head or hands in the engine bay

Replace soon (within the next service):

• Panels that hold open but show slow drift
• Soft or reduced resistance when pushing down
• Panels that feel heavier to lift than they used to

Monitor closely:

• Early softening of resistance without visible drift
• Struts on vehicles 8–10 years old showing no symptoms yet
• Panels used infrequently where failure is less likely to be noticed quickly

When one strut in a pair is replaced, replace both. Struts age at the same rate in the same environment. A new strut paired with a near-failed one creates force imbalance, uneven panel wear, and a second replacement job within months.

FAQs

 

Can a gas strut fail suddenly, without warning signs? 

Physical damage — an impact to the strut body, or a cracked end fitting — can cause sudden failure. But pressure loss from seal degradation almost always shows gradual signs first. The early signs are easy to miss, which is why a periodic check matters.

Is it safe to drive with a failing gas strut?

 For a boot or tailgate, yes — with caution. Avoid opening the panel in situations where a drop could cause injury or damage. For a bonnet, any strut showing failure signs should be replaced before you do any work in the engine bay.

Do all vehicles have gas struts on every opening? 

No. Some older or base-model vehicles use prop rods on the bonnet, and some budget hatches use manual support arms rather than gas struts on the tailgate. If your vehicle has a prop rod on the bonnet by design, that's factory spec — not a failed strut.

How do I know which replacement strut is correct for my vehicle?

 The correct strut must match the Newton force rating, extended/compressed length, and end fitting type for your specific application. Vehicle make, model, year, and the opening it's fitted to are the minimum details needed to confirm the correct specification. Schutts Industrial supplies automotive and industrial gas struts across Australia and can assist with identifying the correct replacement for your vehicle.

Can I replace just one strut if only one has failed? 

Technically yes, but it's not recommended. Struts in a matched pair age at the same rate. If one has failed, the other is likely close. Replacing only the failed strut creates a force imbalance and means a second job shortly after. Replace both at the same time.

Where can I buy replacement gas struts in Australia?

 Schutts Industrial stocks a wide range of automotive gas struts for bonnets, boot lids, tailgates, and canopy applications, with Australia-wide delivery. Their catalogue can be searched by application or specification.