Life behind the wheel doesn’t come without its risks, but sustaining a head injury while unloading your groceries or refilling your windshield wiper fluid shouldn’t be one of them. The hood and liftgate struts found in many of today’s cars, trucks, and SUVs offer a convenient way to access the engine or rear storage area––right up until they don’t. Many drivers can go the life of their vehicle without ever thinking twice about these struts, but when they fail, it can create headaches, both literal and figurative.
It’s easy to develop a false sense of security when your vehicle is in park, but it’s important to remember that the average hood weighs anywhere between 30 and 80 pounds. When something goes wrong, that’s a head injury or smashed finger just waiting to happen, which is why it’s so important to familiarize yourself with this lesser-known component. From examining how hood and liftgate struts work––and how they can fail––to discovering just how easy they are to replace, read on as we cover some basics that’ll have you strutting around your garage like a veteran mechanic.
Struts vs Prop Rods
Before we delve into some hood strut basics, we should make a quick clarification. While struts have long been the go-to choice when it comes to the rear liftgate, their use as a hood support is a little less consistent. Many vehicles––especially older models––rely on a simple prop rod to keep the hood open. This basic metal rod, which must be manually engaged after the hood has been opened, might not be quite as sophisticated as some of the newer designs, but it’s also less prone to the sort of wear and tear that can necessitate replacement.
There’s really no rhyme or reason as to which models are graced with hood struts and which are designed with simpler prop rods, so if the feature is a dealbreaker, make sure to pop the hood and see what you’re working with before investing in a new vehicle. Those looking to upgrade from a prop rod to a struts have plenty of aftermarket products to choose from, with prices usually ranging from $100 to $200. It might fall on the more cosmetic end of the upgrade spectrum, but if you’re the type of driver who spends a lot of time tinkering around under the hood or are a regular at car shows where being able to easily show off the goods under the hood is a prerequisite, it might be worth the investment.
How They Work
Hood struts are actually pretty simple when it comes to their design. In fact, it’s the driver themself that does most of the work. Every time you lower the hood, gas is compressed inside the strut. When you open the hood, this compressed gas can expand. The stored pneumatic energy of this gas exerts enough pressure to keep the piston rod extended until you’re ready to close the hood. As you lower the hood, the gas is compressed again, restarting the process.
Liftgate struts are pretty similar to hood struts but can differ in two important ways. While many vehicles employ the same gas struts on their liftgates as the ones found under the hood, power liftgates have become increasingly popular on newer models. If your vehicle has a liftgate that opens and shuts automatically, odds are you’re dealing with electric or hydraulic struts. Another exception are the struts found on the tailgates of some pickup trucks, which often employ the gas-charged design but in reverse. These struts are intended to help the tailgate gradually lower, which means they don’t require the same power as the liftgate struts found on SUVs, hatchbacks, and wagons.
Why Do They Fail?
The pneumatic and hydraulic principles that allow hood and liftgate struts to work are reliant on one thing: pressure. Whether it’s gas or hydraulic fluid that’s being pressurized, a tight seal is a key part of the process. Struts rely on seals to keep this pressure where it’s supposed to be, but over time, these seals can wear out, developing slow leaks or simply failing outright.
Heat and contamination tend to be the main culprits when it comes to strut failure. The engine bay can reach temperatures of over 200 degrees in the height of the summer, effectively baking the struts and damaging their seals. A dirty engine compartment can also lead to premature failure as dirt, grit, and other contaminants work their way into the seals. Excessive usage or vibrations can also lead to accelerated wear. If you’re popping the hood every other day or subjecting your vehicle to the gauntlet that is off-road driving, expect the struts to respond in kind.
Of course, gradual degradation isn’t the only reason a hood or liftgate strut might fail. A car accident or wayward tool could also cause the strut to be damaged beyond repair, though in those cases, the failure should be quite obvious and sudden. Still, it’s a good reminder to give your hood struts a thorough once-over after an accident, especially any impact that damages the hood or front end. Automakers design their products to protect the driver and passengers, not the vehicle itself, and the crumpling action that’s saved so many lives can lead to a real mess under the hood.
How Long Do They Last?
How long should a driver expect their hood or liftgate struts to last? It all depends on the specific design and how the vehicle is used. Generally speaking, hood struts will last around five to 10 years before they need to be replaced. The size of the struts can also have a noticeable impact on longevity. Smaller struts will typically last longer as they have a shorter stroke than their larger counterparts. This is due to the fact that a longer stroke creates more friction, which can lead to the seals wearing out at an accelerated rate. If you’re installing your own aftermarket struts and looking to maximize longevity, consider opting for a shorter strut.
Because they usually see a more benign environment than hood struts, many drivers report liftgate struts lasting even longer, with a typical replacement cycle of around 10 years or more. In some cases, a driver might go the entire life of a vehicle without needing to replace the hood or liftgate struts, but again, it all depends on how the vehicle is used. The electric or hydraulic system that drives automatic liftgate struts is also prone to failure and should always be inspected if you suspect any liftgate-related trouble.
Signs of Comprised Struts
If you’re dealing with compromised hood or liftgate struts, it usually tends to be a pretty gradual process. Sure, there are examples of instantaneous failure where the hood or liftgate might snap shut without warning, but by and large, the degradation tends to happen in steps. At first, a driver might notice that their hood or trunk will begin to shut slowly on its own as the pressurized gas leaks from the strut. If the ambient temperature is particularly low, you might be able to write this off as a simple matter of thermodynamics as the colder gas struggles to expand, but it should still be treated as a warning sign of impending failure.
If the issue isn’t addressed, that gradual closure can escalate into a sudden problem. A strut that’s about to fail often won’t give any warning. One moment, it’ll be supporting the hood like normal, and the next, it can come crashing down on anyone unlucky enough to be in its way. At this point, it’s really not safe to continue working under the hood until the issue has been addressed.
Finally, there’s the late-stage strut that can’t even pretend to do its job. If the seals have been fully compromised, these struts will often fail to hold up the hood at all. In some ways, this is actually safer than a semi-failed strut because drivers can’t ignore the issue. There’s really no repairing a compromised strut, so don’t expect the problem to resolve itself with anything short of wholesale replacement.
Replacement Options
If your hood or liftgate struts aren’t working quite as well as they once did, it might be time for a replacement. This process is actually relatively simple, with plenty of aftermarket products designed with the average DIY mechanic in mind. There are a few options when it comes to replacing a strut. The simplest would be replacing the cylinder itself, which can usually be done for as little as $50.
When replacing the entire strut assembly there are two choices based on your level of mechanical competency: a no-drill kit and one that requires a little quality time with your power tools. If you do want to go the professional route, expect to pay around $150 per strut. This is a pretty modest investment and costs about the same as the DIY route, though the price can quickly skyrocket if you’re in need of a new pump or motor for a power liftgate. If you’re looking for a cheaper fix when it comes to the hood strut, you can always replace it with a simple prop rod. These old-fashioned components might not be the slickest option, but they do the job just fine.
Don’t Let a Failed Strut Become a Headache
Hood and liftgate struts play an important role when it comes to servicing your vehicle, accessing the cargo area, or showing off that shiny engine block. While it’s easy to neglect these components, that sort of apathy can potentially lead to some very real consequences. Bodily injury is the worst-case scenario, but if your liftgate strut suddenly fails, it could also mean something as expensive as replacing a shattered rear windshield. Strut replacement is well within the reach of the average DIY mechanic, especially since it doesn’t involve messing with any of the parts that are actually responsible for a vehicle’s performance or safety. When you suspect a failing hood or tailgate strut, don’t wait around for it to become a problem. If you catch the issue early enough, you might be able to get away with just switching out the cylinder, but procrastination can easily triple the bill and leave you facing a full replacement.