Bonnet Struts Replacement Guide: When to Replace & How to Choose the Right One
A bonnet that drops without warning is more than an annoyance — it's a safety hazard. Whether yours is struggling to stay open, closing too slowly, or not lifting at all, the fix is usually straightforward: replace the struts. This guide walks you through spotting the signs, selecting the correct part, and doing the job yourself in under an hour.
Signs Your Bonnet Struts Need Replacing
Gas struts don't fail overnight. Pressure loss is gradual, which means the symptoms start subtle before they become dangerous. Here's what to look out for:
- The bonnet won't stay open — the most obvious sign. If you need to prop it up with a rod or your arm, the gas pressure has gone.
- The bonnet lifts slowly or feels stiff — worn struts lose the ability to assist the lift. You'll notice you're doing more of the work than you used to.
- Uneven lift or the bonnet sits slightly misaligned — if one strut is failing faster than the other (common on older vehicles), the bonnet may tilt or feel lopsided when opened.
- Visible oil residue on the strut body — a sign of internal seal failure. Oily streaks along the shaft mean the strut is leaking its pressurised fluid.
- The bonnet slams shut unexpectedly — in colder weather especially, degraded struts lose pressure rapidly. If the bonnet has ever dropped on you, replace both struts immediately.
- The strut shaft is bent or corroded — physical damage prevents smooth movement and can cause binding or misalignment.
Worth knowing: bonnet struts on petrol or diesel vehicles are often exposed to engine heat, which accelerates seal wear. Struts on older high-mileage cars should be inspected as part of any routine service.
When Should You Replace Bonnet Struts?
There's no fixed mileage or service interval for bonnet gas struts — they're replaced on condition, not schedule. That said, most struts begin degrading noticeably between 8 and 12 years, or around 80,000–100,000 miles on vehicles driven regularly in variable climates.
Replace your bonnet struts if:
- Any of the symptoms above are present
- The vehicle is over 10 years old and the struts have never been changed
- You're preparing the vehicle for an MOT (a bonnet that drops during inspection is a fail risk)
- One strut has failed — always replace both at the same time, even if one appears functional. Mismatched pressure causes uneven lift and stresses the bonnet hinges.
How to Choose the Correct Replacement Bonnet Strut
Fitting the wrong strut is the most common DIY mistake. A strut with too little force won't hold the bonnet; too much and it'll fly open or stress the hinges. Here's how to get it right.
1. Match by Vehicle Make, Model, and Year
The safest approach is to choose a strut designed specifically for your vehicle. Vehicle-specific struts are pre-matched to the correct force rating, length, and end fitting. Use your registration or VIN to confirm compatibility.
2. Check the OEM Part Number
Your existing strut will usually have a part number stamped on the barrel or printed on a label. Cross-referencing this number ensures an exact match. For example, many Audi and VW bonnets use struts with the reference 8L0823359.
3. Measure the Original Strut (if the number is gone)
Measure the strut in its fully extended state — this is the extended length. Also note the force rating (measured in Newtons, shown as N on the barrel). If neither is legible, a mechanic or parts specialist can identify the correct spec from your vehicle details.
4. End Fittings Must Match
Most bonnet struts use a ball socket on both ends (10mm ball stud is the UK standard for most passenger cars). Confirm your vehicle uses the same before ordering.
Vehicle-Specific Bonnet Struts — In Stock Now
- BMW 3 Series (E36) Bonnet Gas Struts — £13.90 per pair
- VW Golf MK4 Bonnet Struts — £10.90 per pair
- Audi A3 (8L1, 1996–2003) Bonnet Struts — £10.90 each
How to Replace Bonnet Struts — Step by Step
This is a job most people can do on the driveway with basic tools. No specialist equipment required.
What you'll need: flat-head screwdriver or trim removal tool, safety prop or assistant, new struts.
- Open the bonnet fully and secure it safely. Use a bonnet prop rod if your vehicle has one, or ask someone to hold it. Never work under an unsupported bonnet.
- Locate the existing strut end fittings. There will be a clip or retaining tab at each end — typically a C-clip or push-fit plastic clip on the ball stud.
- Remove the lower end first. Slide the flat-head screwdriver or trim tool behind the clip and lever it free. The strut end will pop off the ball stud. Do the same at the upper end.
- Remove the old strut and set it aside. Take note of the orientation — the shaft (narrower end) typically faces downward on bonnet struts, but check your vehicle before fitting.
- Fit the new strut. Press the upper socket onto the ball stud first until it clicks securely. Then press the lower end into place. You should feel a positive click at both ends.
- Repeat for the second strut. Replace both at the same time. Always.
- Test the bonnet. Lower it gently to within 30cm of the closed position, then release. It should hold open firmly with no drift. If it sags, check the fitting is fully seated.
Tip: new struts can be slightly stiffer than expected for the first few open/close cycles. This is normal — the seals are settling.
How Much Should Bonnet Strut Replacement Cost?
| Route | Parts Cost | Labour | Total Estimate |
|---|---|---|---|
| DIY (Autorce struts) | £10.90 – £13.90 | £0 | £10.90 – £13.90 |
| Independent garage | £15–£35 (OEM parts) | £30–£60 | £45–£95 |
| Main dealer | £30–£80 (OEM parts) | £50–£120 | £80–£200+ |
For most popular vehicles, fitting bonnet struts yourself saves the majority of the cost. The job takes less than 30 minutes once you have the right parts in hand.
Ready to Order?
Autorce stocks bonnet gas struts for a wide range of UK vehicles, with vehicle-specific options and fast despatch. All struts are supplied as matched pairs unless otherwise stated, and product pages include compatibility notes to help confirm fitment before you buy.
Frequently Asked Questions
How do I know if my bonnet struts have failed?
The most obvious sign is a bonnet that won't stay open on its own. Other signs include a slow or heavy lift, visible oily residue along the strut shaft, or the bonnet dropping shut unexpectedly. If any of these apply, the struts have lost their gas pressure and need replacing.
Do I need to replace both bonnet struts at the same time?
Yes — always replace both together, even if only one appears to have failed. Mismatched pressure causes uneven lift, stresses the bonnet hinges, and usually means you'll be doing the job again within months.
Are bonnet gas struts the same as hydraulic bonnet struts?
The terms are often used interchangeably. Gas struts use compressed nitrogen and are standard on UK passenger cars. True hydraulic struts use oil pressure and are typically found on heavy commercial vehicles.
Can I replace bonnet struts myself, or do I need a garage?
Most bonnet struts can be replaced at home with no specialist tools — just a flat-head screwdriver and a safe way to support the bonnet. The job typically takes 15–30 minutes.
How long do bonnet struts last?
Most bonnet struts last between 8 and 12 years under normal use. There is no fixed service interval — replace on condition, not mileage.
How do I find the right bonnet strut for my car?
Match by vehicle make, model, and year. You can also cross-reference the OEM part number on your existing strut, or measure the extended length and note the Newton (N) rating on the barrel. Browse our full bonnet struts range to find your vehicle.
