How to Fix Broken Car Seat Springs: A DIY Repair Guide
Car seats in older vehicles, especially classics like Mercedes, are renowned for their durable upholstery. However, the seat springs underneath can sometimes succumb to wear and tear, particularly in cars over 20 years old. Mercedes-Benz seats are famously upholstered with MB Tex, a robust vinyl that resists aging. Yet, even with such resilient upholstery, the seat spring boxes can weaken over time. This is often due to the combined factors of age and the weight of occupants, leading to sagging and broken springs, especially on the driver’s side where there’s frequent entry and exit.
A new seat spring box can be a costly replacement. This guide offers a simple, cost-effective DIY fix for broken car seat springs, utilizing readily available materials and basic tools. In this repair, we’ll repurpose old Mercedes fuel injection line to create a durable and functional solution. Follow these steps to restore the comfort and support of your car seat.
Before you begin, remember these important safety tips:
- Always recycle used fluids at a certified recycling center.
- Avoid spilling fluids on yourself, others, or the ground.
- Wear safety glasses whenever you are working on or under your vehicle.
- Secure your car with wheel chocks and approved jack stands for safety.
Step 1: Seat Removal
The first step is to remove the car seat from your vehicle. Begin by locating and removing the two front bolts that secure the seat to the floor.
Step 2: Accessing Rear Bolts
Slide the seat forward completely. Use the seat height adjustment handle to raise or move the seat forward further. This step is crucial to gain access and clearance to reach the two rear bolts that are still holding the seat in place.
Step 3: Detaching Rear Bolts and Seat Belt Guide
Now, remove the two rear bolts that secure the seat to the floor. Additionally, locate and remove the seat belt guide anchor bolt, typically found on the transmission tunnel.
Step 4: Final Seat Disassembly and Removal
Raise the seat back to an upright position. Fold up the armrest (if applicable) and lower the headrest to their most compact positions. Carefully remove the entire seat from the vehicle. If your seat has electrical connections (for seat heaters or adjustments), disconnect them at this stage. Place the seat upside down on a protected surface, such as a towel or blanket, to prevent any scratches or damage to the upholstery.
Step 5: Identifying the Broken Spring
With the seat removed and inverted, you can now clearly see the seat spring box. In many cases, the broken spring will be evident, especially on the driver’s side outer edge, closest to the door. This area is subjected to the most stress from entering and exiting the car, making it a common point of failure. The goal now is to find a way to reconnect the broken pieces, prevent future separation, and maintain the original spring rate for optimal seat comfort.
Step 6: Preparing the Collar – Utilizing Fuel Injection Line
The solution involves creating a collar to encase the broken ends of the spring. Old fuel injection line from a Mercedes 617 engine is an ideal material for this. The inside diameter of fuel injection line is quite small. To make it suitable for use as a spring collar, you need to enlarge its inner diameter.
Step 7: Enlarging the Fuel Line Diameter
Select a drill bit that is slightly smaller than the outside diameter of the fuel injection line. Use this drill bit to carefully ream out the inside of a section of fuel line. Cut off a piece of the reamed fuel line to create the collar. This process results in a robust and stable collar for the spring repair.
Step 8: Grinding the Spring Ends
To ensure a snug fit for the collar, you might need to grind down the broken ends of the seat spring slightly. This is a process of trial and error – try fitting the collar, and grind a little more if needed. The aim is to achieve a tight fit on both ends of the spring within the collar.
Step 9: Assembling the Collar and Securing the Repair
Once the spring ends are prepared, install the fuel line collar, ensuring a tight fit over both broken ends. To further secure the repair and prevent the spring from pulling out of the collar, use safety wire to wrap around the spring and collar. This step is essential. When the seat is in use, the spring will flex, and without the wire, it could separate from the collar. The safety wire maintains the correct spring angle and prevents separation, while the rigid collar ensures the spring retains its intended stiffness and spring rate. This method effectively restores the seat’s original feel, making it feel nearly new again, or at least as good as it can be without a broken spring.
Step 10: Reinstallation and Enjoyment
If you discover multiple broken springs, repeat this repair process for each one. After completing the repairs, the final step is to reinstall the seat back into your vehicle. Secure it with the bolts you removed earlier. Once everything is tightened and reconnected (including any electrical connections), you can enjoy the renewed comfort of your car seat!
