Mercury Mountaineer Liftgate Glass Support Strut Replacement Cost

Many of the vehicles that feature a liftgate are fitted with a window (the liftgate glass) that swings outward and upward for easy access to the rear cargo compartment. When opened, the glass is supported by a pair of pneumatic arms, or struts. These liftgate glass support struts become fatigued with age and constant wear, and occasionally need to be replaced.

A liftgate glass support strut is a long, slender cylinder with a solid rod running through the center as a sort of plunger. The strut is gas filled (pneumatic) so that when the rod is pushed into the cylinder, the gas is compressed. This serves to force the rod out of the cylinder, thereby extending the length of the strut. The action is similar to that of a shock absorber. The force exerted by the struts is matched to the weight of the glass and the leverage produced when it is open. When the glass is closed, the struts are compressed. When the glass is unlatched, the struts naturally decompress and extend to open the glass.

The primary symptom of failing support struts is nearly always a window that will not stay open. Over time, the struts wear out and weaken, and the force they are able to exert on the glass diminishes. Most vehicle owners first notice that the glass does not open as quickly as usual when the struts are near the end of their useful life. As the condition worsens, the window will tend to fall down when opened, though the problem may, for a time, be intermittent. Cooler temperatures tend to exacerbate the problem.

If the liftgate glass support struts fail, there is no reason that the vehicle cannot be driven. But failing support struts, whether on the liftgate glass, on the liftgate itself - or on a hood or deck lid - pose a risk for head and neck injury. Care should be exercised if the struts are worn past their ability to keep a body panel supported.

While there is no regular replacement interval scheduled for the liftgate glass support struts, it is not uncommon to have to replace them at or around 100K miles on some vehicles. In other cases the struts have been known to last far longer.

The diagnosis of failing liftgate glass support struts is simple. A technician will inspect the way the glass opens and closes. If the glass does not stay open, or if it is too easy to close, the struts will need to be replaced.

To replace the liftgate glass support struts, a technician will lift the glass and hold it open it with a rod so that it does not fall when the struts are removed. The ends of the struts are fastened to the inside of the liftgate frame adjacent to the glass panel with a ball and socket joint that allows the strut to pivot. On most vehicles, the ball remains on the liftgate frame and the strut is removed when the technician manipulates a spring clip that retains the ball in the socket. On some vehicles, however, the ball remains in its socket and is unscrewed from the liftgate. The same procedure is followed on the glass side of the strut. With the old strut removed, the new one is installed in its place.

Both support struts on a panel usually wear out at the same pace. RepairPal recommends that they be replaced as a pair. If the combined force of the struts is not enough to support the glass (or other panel), the symptoms will simply diminish, not go away. Excess stress is put on the new strut when only one is replaced. And if one strut is stronger than the other, they will apply a twisting force on the panel causing misalignment and possibly damage. Also, the replacement struts should be OEM quality since they are specific to their application.

Any body panel that uses support struts - hood, deck lid, liftgate, or liftgate glass - relies on the proper amount of combined and equal force from both struts. If the force is not sufficient or equal between them, the panel will not open and close properly and can cause damage to the vehicle. Moreover, when the struts go bad, they may hold up the panel momentarily and let it fall when someone is underneath. Failing (or improper) struts can cause severe injury to the head, neck, and hands.

An intermediate DIYer can replace the liftgate glass support struts with little problem as long as the glass is supported properly. Care should be taken when manipulating the spring clips that hold the ball in the socket. They do not need to be removed from the strut, yet many novices lose the clips. Care should also be exercised when first closing the glass to make sure the tension is even and the glass is aligned properly.