A cracked bumper is one of the most common car body repairs carried out by smart (Small to Medium Area Repair Techniques) repair operatives. Bumpers are designed to handle low impact collisions such as being hit by a shopping trolley, low speed scraping collisions with other vehicles and car park barriers and other minor impacts. Often this kind of accident results in dents, scuffs and scrapes which can be repaired quickly and easily by a mobile car body repair technician with some car body filler, primer, paint and lacquer. Sometimes however, a crack will appear and split the bumper and this has to be dealt with differently.
If a cracked bumper is not repaired or the repair is carried out with normal filler, the structural integrity of the bumper is compromised. It is essential that the bumper crack is treated and rejoined with a hard yet flexible resin. There is a specific technique used to accomplish this which should be carried out every time.
Usually the crack does not look severe, it often has the appearance of a hairline crack and it is tempting to run a little filler over it and treat that as repaired. The result of this is that the next time the bumper is put under any pressure at all, the crack will reappear and often widen. The crack must be widened, effectively worsening the damage, initially so that there is enough of a gap for the resin to fit in. A hole is drilled at each end of the crack, half on and half off the very end. This permanently stops the crack from running again. Next, a v-shaped groove must be made right down the centre of the crack, wide enough for the drill bit to make a hole without going off the edge of the crack.
A series of holes, one on each side of the crack every inch or so along the whole length of the crack need to be drilled. A strip of mesh is then placed on the inside of the bumper all along the damage – this will hold the resin in place while it hardens and can be left there afterwards. A mix of resin and hardener, specifically formulated for bumper repairs such as this, is then injected into each of the holes that have been drilled. The mesh backing provides the purchase needed to prevent the resin going straight through. The aim here is to effectively “stitch” the repair together.
After applying the resin, a body filler spreader (or ideally specialist contouring film) is used to smooth the repair on the top side of the bumper to minimise the sanding that will be required later. Care must be taken as the bumper resin can melt if sanded too vigorously. After the resin has fully hardened the bumper is structurally sound again and can be sanded, filled, primed, painted and lacquered as normal. Result – a perfect bumper repair