Exhaust Problems: Signs of a Blowing or Failing Exhaust

Noise: the first and clearest warning

A blowing exhaust is usually loud. A hole or split in the pipe or silencer lets the gas escape before it reaches the quieter parts of the system, so the engine sounds throaty, rasping or ticking, especially under acceleration or when cold. A small leak near the manifold can sound like a fast tapping or hissing.

A deeper boom or drone at cruising speed usually means a silencer box has rusted through. A rattle that comes and goes can be a loose heat shield, a broken hanger or a failing internal baffle.

• Roaring or rasping that worsens as you accelerate
• Ticking or tapping from the engine bay that fades as it warms up
• Rattle over bumps, suggesting loose parts or a broken mounting
• Hissing or puffing from beneath the car

Smell, fumes and other symptoms

Exhaust gases contain carbon monoxide, which is poisonous and has no smell of its own. If you smell fumes inside the car, or a leak seems to be getting into the cabin, open the windows and have the car checked straight away. Do not carry on driving with fumes coming into the cabin.

Other signs include a drop in performance, worse fuel economy, a warning light on the dashboard, or soot marks around a joint where gas is escaping. Sometimes a leak upstream of the oxygen sensor can confuse the engine management and cause running problems.

Hanging pipes and corrosion

Exhausts are held up by rubber hangers and brackets. When one breaks, the weight of the system drags the rest down, which causes more stress and can tear the pipe. A system that is sagging or dragging on the road is a hazard to you and other road users, so do not leave it. If a section is hanging, stop somewhere safe rather than risk it detaching.

Corrosion comes from the inside as well as the outside. Short journeys let moisture build up inside the system, and road salt and wet weather attack the outside. Cars driven near the coast or on gritted roads in winter, as we see around Tyneside, may find surface rust develops quickly.

How exhausts affect the MOT

The MOT includes checks on the exhaust system. A tester looks for leaks, insecure mountings and excessive noise, and measures emissions. A system that is leaking, missing a part or obviously damaged can lead to a fail.

Rules and test limits are updated from time to time, so check the current requirements for your vehicle rather than relying on a general guide. If you suspect a problem, getting it looked at before the test avoids an unwelcome failure.

Exhaust repairs or replacement?

Repair is often possible when damage is limited, such as a small hole, a split joint, a broken hanger or a loose clamp. A repair works if the surrounding metal is sound. Where the pipe is thin and rusted along its length, a patch will just fail again next to it.

At Banks of the Tyne in Hebburn we handle both exhaust repairs and exhaust replacement. After an inspection on a ramp we can explain which you need. Cost depends on the make and model, how much of the system is affected and whether it includes the catalytic converter, so we explain it at the estimate rather than guess.

Frequently asked questions