Gas springs for the engine bonnet serve a straightforward but safety-critical function: they hold the bonnet open at a fixed angle while you work underneath, without relying on a mechanical prop rod that can be dislodged by accidental contact. A gas spring consists of a sealed nitrogen-charged cylinder and piston rod, and it fails in one of two characteristic ways. The more sudden failure mode is a snapped or bent rod, often from being forced beyond its designed travel arc. The more gradual failure is nitrogen leakage through the end seals — this typically manifests as a bonnet that no longer holds itself fully upright, dropping slowly over a period of minutes or requiring a prop rod to be held safely open. At cold temperatures this loss of gas pressure is exaggerated, so a bonnet that barely holds in summer may drop alarmingly in winter. Because gas spring travel, compressed and extended lengths, ball-stud diameter, and mounting eye geometry all vary by vehicle, the OE reference is the reliable way to confirm a correct replacement. BMW, Volkswagen, and Audi are the highest-volume applications in the fitment data, reflecting premium European vehicles where gas-assisted bonnet supports are standard. Stabilus is the dominant OE supplier for European passenger cars; Magneti Marelli covers Italian and French applications widely.
Bonnet gas springs are vehicle-specific — the compressed and extended lengths, gas charge pressure, ball-stud diameter, and end fitting geometry are all defined by the body engineering of each model. Use the make, model, and production year on this page to display the TecDoc OE references for your vehicle. Bonnets often use two gas springs in parallel, and both should be replaced together when one fails to avoid imbalanced lifting force. The OE reference stamped on the body of the existing spring is the fastest cross-check.
OEM gas springs from Stabilus or Magneti Marelli are charged to the precise gas pressure and machined to the dimensional tolerances that match the original bonnet weight and hinge geometry. Quality aftermarket replacements from the same category suppliers are engineered to equivalent specifications. Very cheap alternatives may be undercharged from the factory, meaning the bonnet appears to hold open initially but drops more quickly with temperature and age as the limited gas volume dissipates through the seals faster than a correctly rated unit.
Yes, replacing both as a pair is strongly recommended. The two springs share the lifting load equally when balanced, but if one is significantly weaker than the other — which is typical when one has already lost gas pressure — the bonnet can open unevenly, putting lateral strain on the hinge pins and the remaining spring. Because both springs age from the same heat cycles and environmental exposure, if one has failed the other is rarely far behind.
The clearest sign is a bonnet that no longer holds itself open independently, dropping slowly on its own or requiring manual support to stay raised. At cold temperatures, the problem is more pronounced — a spring that barely holds on a warm summer day may let the bonnet fall on your head in winter. A bent or kinked piston rod, visible when the bonnet is open, indicates physical damage from over-extension. Corrosion on the cylinder body can also cause seal failure and is worth inspecting if the vehicle is used regularly in coastal or heavily salted road environments.
Showing 100 of 1,870 Bonnet gas spring OE numbers. Enter the OE on the main OE search to jump to any reference.
