Exhaust Parts with Fitting Position Front Axle

Exhaust hangers and exhaust mount bushes are the flexible mounts that suspend an exhaust system beneath the vehicle. They hold the pipes, mufflers and other exhaust components in position, absorb engine and road vibration, and allow the exhaust to move and expand as it heats up. When these bushes harden, crack or tear, the exhaust can sag, knock against the body or chassis, and transmit vibration and drone into the cabin. Fitment is specific to each vehicle and mounting point, so use the vehicle search to find exhaust mount bushes to suit your vehicle.

What Do Exhaust Mount Bushes Do?

An exhaust system runs from the engine to the rear of the vehicle, and it is attached rigidly only at the engine end. Along the rest of its length, it hangs from the underside of the vehicle on a series of flexible mounts. Metal hooks or rods welded to the exhaust pass through rubber or polyurethane bushes, which are in turn attached to brackets on the body or chassis.

Those bushes do several jobs at once. They support the weight of the exhaust, keep it at the correct distance from the floor, fuel tank, chassis and other components, and stop vibration travelling from the exhaust into the body. Because the engine rocks on its mounts, the exhaust moves with it, and the bushes allow that movement without letting the exhaust strike anything around it.

Why Exhaust Systems Need Flexible Mounts

An exhaust system gets extremely hot in operation and expands as it does. A long steel exhaust grows noticeably in length between a cold start and full operating temperature, then shrinks again as it cools. If it were bolted rigidly along its length, that expansion would load the mounts, joints and pipes with every heat cycle, eventually cracking welds or brackets.

Engine movement adds to this. Every time the engine twists under acceleration or braking, the front of the exhaust moves with it. Flexible mounts let the exhaust follow that movement and accommodate its expansion, while still holding it securely in place. A healthy set of exhaust mount bushes is what allows the exhaust to move within its intended range without hitting anything.

Signs Your Exhaust Mount Bushes May Be Worn

Common signs include a knocking or banging from underneath the vehicle over bumps, as the exhaust swings and strikes the body, chassis or heat shields. You may notice more vibration or a droning noise through the floor at certain engine speeds, particularly at idle or when the engine is under load.

A visual check from underneath often confirms the problem. Look for bushes that are cracked, split, stretched or hanging lower than others, and for any that are missing entirely. An exhaust that sits lower than it should, or rests on a heat shield or crossmember, points to a failed mount. Shiny or polished marks on the exhaust, body or chassis indicate where contact has been happening.

Other Possible Causes

Knocks and vibration from underneath can also come from loose heat shields, worn engine or transmission mounts, worn suspension bushes and driveline components. A blowing exhaust joint or a cracked pipe can sound like a vibration problem but needs a different repair. Have the cause confirmed before replacing parts, especially if you notice exhaust fumes in the cabin, which should be checked straight away.

Why Exhaust Mounts Wear Faster in a 4WD

Exhaust mounts on a 4WD face harsher conditions than those on a vehicle driven only on sealed roads. Corrugations and rough tracks keep the exhaust swinging and bouncing on its mounts, and every movement stretches and compresses the bushes. Water crossings, mud and dust add contamination, while heat from the exhaust itself ages the rubber from the inside.

Off-road driving also adds physical risk. Exhaust components and hangers often sit low under the vehicle, where they can be struck by rocks, logs or ruts. A heavy impact can stretch or tear a bush, or bend a hanger rod, even if the exhaust itself is undamaged. Checking the exhaust mounts after rough trips helps catch damage before the exhaust drops or strikes something.

Rubber or Polyurethane Exhaust Mount Bushes?

Original exhaust mount bushes are usually rubber, which absorbs vibration well and keeps exhaust noise out of the cabin. Over time, heat from the exhaust and exposure to water, oil and road grime harden and crack the rubber, and the constant weight of the exhaust stretches it until the system sags.

Polyurethane exhaust mount bushes are firmer and generally more resistant to heat, oil and weathering, so they tend to hold their shape and keep the exhaust at its correct height for longer. The trade-off is that a firmer bush can transmit more exhaust vibration into the body. How noticeable that is depends on the vehicle, the mount location and the exhaust system fitted. For mounts close to the engine, where heat is greatest, durability is often the deciding factor.

Exhaust Mounts After Exhaust Upgrades

Aftermarket exhaust systems can differ from the original in weight, shape and the position of their hanger rods. A heavier system loads the mounts more, and hanger rods in a slightly different position can pre-stretch the bushes before the vehicle has moved.

When an exhaust system is changed, check that each hanger lines up naturally with its mount, without the bush being twisted or stretched. Check the clearance between the new system and the floor, fuel tank, chassis, driveshaft and any other components through suspension and engine movement. Fitting new mount bushes at the same time as a new exhaust gives the system a sound starting point.

Fitting Exhaust Mount Bushes: An Overview

Exhaust mount bushes are usually fitted by lifting the weight of the exhaust slightly, then sliding the old bush off its hanger rod and bracket, and fitting the new one in its place. Some bushes are retained by bolts or brackets that need to be undone. A lubricant suited to the bush material can make it easier to slide bushes onto hanger rods, but check that it will not damage the bush.

Only work on the exhaust when it is completely cool, since it can stay hot enough to cause burns long after the engine is switched off. Support the vehicle securely on rated stands before working underneath. Replace bushes one at a time where possible, so the exhaust remains supported, and check that the exhaust sits level and clear of all surrounding components once the work is complete.

Choosing the Right Exhaust Mount Bush Kit

Exhaust mount bushes vary in shape, size, hanger rod diameter and the distance between mounting holes. Some vehicles use several different bush types along the length of the exhaust, and a bush that suits one position may not suit another. Confirm your vehicle's make, model, year and engine before ordering, and identify which mounting points need attention.

If several bushes have failed, replacing all of them at once is often worthwhile, since they are usually the same age and have been exposed to the same conditions. A new bush beside an old, stretched one can leave the exhaust sitting unevenly.

Shop Exhaust Mount Bushes with Formula 4x4

Start by confirming that the knock or vibration is caused by worn exhaust mounts rather than loose heat shields or other components. Search by your vehicle to find exhaust mount bushes to suit it, and check which mounting positions need replacing. If you are unsure which part your vehicle needs, contact the Formula 4x4 team.