Car longeron rear and front

How to detect a faulty frame side rail?

In most cases, the frame side rail cannot be inspected without removing it from the vehicle. Therefore, unassisted assessment of the state of the component is usually limited to examining the geometry of the car body. Make sure that all doors close with the same force applied, and are at the same level relative to the car body. Then, using a measuring tape, measure the distance between the shock strut mounts, the wheel track width, the diagonals of the doorways, and compare the results with the data specified in the technical documentation to the vehicle. More detailed check will require special test benches; therefore, it is best to seek the assistance of a service station.

You may notice that the frame side rail may need diagnostics by the following symptoms:

• the vehicle pulls to one side when moving;
• tires wear unevenly;
• doors, bonnet and trunk lid do not close tightly;
• vibration is felt on the steering wheel while driving at high speeds.

The reasons of frame side rail malfunctions

The frame side rail is a load-bearing element of the car body that withstands the major impact forces during a collision. Therefore, the most common reason of its failure is an intensive physical impact in an accident. After a road accident, the component may be deformed or crack.

Frame side rails may also get bent due to frequent vehicle use in the conditions of poor quality roads, or in off-road conditions, because when the car runs over bumps and potholes, especially at high speed, the components are to withstand high loads.

Exposure to moisture and thawing chemicals may lead to frame side rail corrosion over time. To prevent it, eliminate minor cracks and paintwork chips immediately after discovery.

Repairing the frame side rail

Repair of frame side rails requires the use of special expensive equipment, therefore, it is only possible to be done in the conditions of a service station. The amount of work and the choice of restoration methods will depend on the type and the extent of damage.

In case of perforation corrosion, if it didn't spread over the entire surface of the component, the frame side rail may be repaired with gas or electric welding. The defective area is cleaned, and a patch is welded over it, then the welding joints are covered with anti-corrosion compounds, for example, bituminous joint filler.

Small deformations are eliminated by pulling out on a special bench. Severely deformed areas, if their overall area is not large, are cut out, and new pieces are welded on instead of them.

In case of more serious damage, even the high-quality repair does not guarantee the original strength of the vehicle, therefore, the frame side rail is to be replaced.

Replacing the frame side rail

You cannot replace the frame side rail yourself if you do not have appropriate skills and equipment. To access the component, you will need to dismantle the engine and the radiators, disassemble the front suspension, and disconnect the subframe and other components. After that, the damaged frame side rail is levelled on a special bench to meet the parameters of suspension and the geometry of the car body, and only after that, the frame side rail is replaced.