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Q

My Morris Marina’s very noisy on bad surfaces and potholes set off a bonejarring crash that seems to go right through the bodywork. Can you give me any pointers as to what might be wrong?

Leonard Coles, Louth

Ed says A

Age and mileage get to a car’s suspension, robbing it of its once-silent riding qualities. We’ll generalise a bit here, so as to cover as many types of suspension as possible. Wishbones, control arms, leaf springs and dampers usually pivot in bonded rubber bushes. Eventually, the rubber shrinks, stretches, becomes soft or hard, or goes a funny shape. At this point unintended movement creeps in, causing harsh crashing noises as well as sloppy handling, unexpected under-or oversteer, wandering on bad surfaces, etc. Badly worn dampers themselves can knock, too. Consider also the kingpins, balljoints and steering rods: all contain wearing parts and if allowed to wear out, they also end up with play that causes impacts as the suspension is shaken around. A loose wheel bearing, broken or worn subframe mounts or fractures in the subframe or suspension mountings may also be a possibility. Check the top strut bearing of Macpherson struts, too. Most things can be checked by jacking-up each wheel and shaking it, prying it or gripping it and moving it back and forth through its steering arc. Remember that when replacing dampers, the mountings are

tightened until the nut comes to a positive stop, not just until it feels ‘quite tight’. Otherwise they’ll knock on bumps.

Don’t overlook the possibility that the noise is coming solely from the bodywork. Doors bash against their frames; catches may be too loosely adjusted to hold doors and boots silently against their rubber seals; bonnet hinges can wear and rattle up and down. Mechanisms inside doors are fertile sources of noise, too, as are exhausts that bang against the floor and petrol tanks whose straps have corroded and stretched. Bumpers may clatter due to loose mountings or missing corner brackets.

Get an assistant to accompany you on a drive and to move around the car trying to identify the location of the noise(s). Empty the boot, glovebox and ashtray of all detritus first, of course.