How to replace a V-ribbed belt

When to replace a V-ribbed belt

A V-ribbed belt wears as it runs and ages with heat. As a rough guide, V-ribbed belts are often replaced after 100,000 to 150,000 km. Schedules differ between vehicle manufacturers and engines: some give a distance or a time at which the belt is replaced, others only have it inspected at each service and replaced according to its condition. The schedule for your vehicle decides, and a belt that is damaged or worn is replaced whatever its age.

Have the belt and its drive inspected when you notice one of these:

• Squealing or chirping from the belt drive, above all at a cold start, in wet weather or when a consumer such as the air conditioning switches on
• Cracks across the ribs, pieces missing from the ribs, ribs that have come apart from each other, or frayed edges
• A hardened, shiny surface on the ribs or the back of the belt
• Oil, coolant or another fluid on the belt
• The belt runs off-centre on a pulley, flutters or has moved sideways out of some grooves
• Depending on which units the belt drives: the battery or charging warning comes on, the steering becomes heavy or the coolant temperature rises

A belt can be worn without showing cracks: on many current belts the ribs wear down gradually, so that the belt sits deeper in the grooves and grips less. This wear is hard to judge by eye; a workshop can measure it with the belt maker's gauge. Noise and slipping have other causes too: a tensioner that no longer holds the belt tight or damps its movement, an idler pulley or a driven unit with a worn bearing, a freewheel pulley on the alternator that has seized, pulleys that are out of line, and fluid that reaches the belt from a leak. A new belt does not cure these faults, and they can ruin a new belt quickly.

Do not go on driving with a V-ribbed belt that is torn, frayed, has lost pieces or has come off. Depending on the engine, the battery is then no longer charged, the steering assistance can fail and the engine can overheat quickly. On some engines the remains of a torn belt can get into the timing drive and cause severe engine damage. Stop the engine and have the vehicle recovered.

Before you start

A belt drive that starts to move can trap and sever fingers, and a tensioner is under strong spring force: a tool that slips off it is thrown back hard. Work only with the engine stopped and secured against starting, keep your fingers out from between the belt and the pulleys, hold the tensioner's tool so that your hand is not in its path if it slips, and never release a tensioner suddenly.

• Obtain the vehicle manufacturer's procedure before you start: the belt's routing, the kind of tensioner and how and in which direction it is released, the tool it needs and whether it can be locked, the parts that have to be removed for access, and the tightening specifications. If you cannot obtain it, leave the job to a workshop: the ways of releasing a belt differ too much between engines to be guessed.
• Find out how your engine's belt is kept tight. Most engines have an automatic tensioner with a spring or a hydraulic damper, which is turned or pushed against its force to slacken the belt. Some have a tensioner or a driven unit that is adjusted by hand and then tightened in place. Some have an elastic belt without any tensioner, which is stretched over the pulleys and can be fitted only with the fitting tool intended for it.
• Find out how many belts your engine has. Some engines drive all units with one belt, others have a second belt, for example for the air conditioning compressor, and an outer belt may have to come off before the inner one can be reached. Each belt has its own part number, routing and way of being tensioned.
• Find out what is in the way. On many vehicles the belt is reached through the wheel arch after a wheel and a liner have been removed, or from below after an undertray has been removed. On some engines the belt passes around an engine mounting, which then has to be taken out with the engine supported. If your vehicle needs that and you do not have the equipment the vehicle manufacturer specifies for supporting the engine, leave the job to a workshop.
• On a vehicle whose belt drives a starter-generator, or that is a hybrid, the vehicle manufacturer's procedure for making the electrical system safe comes first, and the belt and its tensioner can differ from what this guide describes. Follow that procedure exactly, and leave the job to a workshop if you cannot. Do not touch orange high-voltage cables or the components they connect.
• Park the vehicle on firm, level ground with the parking brake applied. Switch off the ignition and keep the key or remote away from the vehicle, so that the engine cannot be started. Follow your vehicle manufacturer's instructions for service work on engines that start automatically, and disconnect the battery if those instructions call for it.
• Let the engine cool until the parts around the belt can be worked on without burns. An electric cooling fan can start by itself even with the ignition off: keep hands and tools clear of it.
• If the vehicle has to be raised, raise it only at the points the vehicle manufacturer gives, on ramps or axle stands made for its weight, with the wheels that stay on the ground chocked. Never go under a vehicle that is held up by a jack alone.

Choose the right belt

V-ribbed belts differ in the number of their ribs, their length, their material and their construction. A belt that can be got onto the pulleys is not therefore the right one: a belt that is too long may not be kept tight, one that is too short may overload the bearings of the units or may not fit at all, and a belt with too few ribs may not carry the load. Fit only a belt listed for your engine and its equipment.

Select your vehicle with the selector on this page to find the part numbers suppliers list for its engine. On the vehicle's part page, each part number is shown with the specifications its supplier states: for example the number of ribs, the length and the material, and for some part numbers the material of the tensile cord or that the belt is double-sided.

• The same engine often takes belts of different lengths depending on its equipment: with or without air conditioning, with one alternator or another, with or without a power steering pump. Where a supplier states conditions for a part number, such as the equipment, a production period or an engine number range, the vehicle's part page shows them with that part number: check them against your vehicle. If what is stated does not settle whether the belt fits, ask the supplier or the vehicle manufacturer before you buy.
• Where an engine has more than one belt, make sure which belt each part number is for, and do not assume that part numbers for different belts are interchangeable.
• A double-sided belt has ribs on both sides and drives pulleys with its back as well. Take one only where it is listed for your engine, and never replace it with a belt that is ribbed on one side.
• An elastic belt and a belt for a drive with a tensioner are not interchangeable, even where the number of ribs and the length appear to match. The specifications listed above do not always say whether a belt is elastic: look for it in the supplier's own description of the part number, ask the supplier or the vehicle manufacturer if that does not say, and ask the supplier whether the fitting tool is supplied with the belt or has to be obtained separately.
• Where several part numbers are listed for the same position, compare the conditions each supplier states, and ask the supplier or the vehicle manufacturer if they do not show which one is for your vehicle. A belt is also sold in sets with a tensioner and pulleys; this guide covers the belt alone.

Compare the new belt with the old one before you fit it: the number of ribs has to be the same. Do not take the old belt as the specification, though: a used belt has changed with wear, and a belt that was fitted earlier may itself have been the wrong one. Use a part number listed for your engine whose stated conditions match your vehicle and its equipment, and ask the supplier or the vehicle manufacturer if they do not settle whether it fits; a difference between the two belts needs the supplier's or the vehicle manufacturer's confirmation.

All V-ribbed belt OE numbers in the catalogue

Remove the old belt

1. Before you remove anything, switch off the ignition, make sure that the engine cannot be started, as described under Before you start, and let the engine cool. Where the bonnet has to be open, make sure that its stay or struts hold it securely. If the vehicle has to be raised, raise and support it as described under Before you start, and check that it stands securely.
2. Remove the parts that are in the way as the vehicle manufacturer describes: depending on the vehicle, an engine cover, an undertray, a wheel and the wheel arch liner, or an air duct. Release any clip or lock before you pull at a part, and keep the parts and their fixings together.
3. Where the vehicle manufacturer's procedure requires an outer belt to come off before the belt you are replacing, deal with the outer belt first: record its routing and remove it as described in the following steps, in the way its own tensioning requires, and keep the belts apart. If the outer belt is to be refitted and the vehicle manufacturer permits that, mark its direction of rotation on its back before you remove it. Record the routing of each belt before you slacken it: take photographs or draw a sketch that shows the path around every pulley and which pulleys the ribbed side runs on and which the back. Compare your record with the routing in the vehicle manufacturer's procedure or on the routing label in the engine compartment, if the vehicle has one; if they differ, the belt may have been fitted wrongly before, and the manufacturer's routing for your engine and equipment decides.
4. Where the engine has an automatic tensioner: put the tool the vehicle manufacturer specifies on the tensioner at the point provided for it, make sure that it is seated fully, and turn or push the tensioner smoothly against its force in the direction the procedure gives, only as far as needed to slacken the belt. Do not go on turning against the stop. If the tensioner has a provision for locking, lock it with the pin or tool the procedure names.
5. With the belt slack, slide it off the pulley the vehicle manufacturer's procedure names; if it names none, find that out from the vehicle manufacturer's information first. Then let a tensioner that is not locked return slowly under control until it rests, and take the tool off.
6. Where the belt is tensioned by hand: loosen the fixings of the tensioner or of the unit that is moved for tensioning, in the order and only as far as the vehicle manufacturer describes, and turn the adjuster back or move the unit until the belt is slack. Do not lever against a unit's housing, its pulley or its connections.
7. Where the engine has an elastic belt: remove it as the vehicle manufacturer describes. An elastic belt that is being replaced is as a rule cut through for removal; make sure first that it is the right belt and cut only the belt, without touching a pulley, a hose or a cable. Never lever an elastic belt off or on with a screwdriver or a similar tool.
8. Take the belt out of the drive completely, guiding it past the fan, the hoses and the engine mounting without force.
9. Inspect every pulley of the drive and check it as the vehicle manufacturer's procedure describes for its design. None may be cracked, chipped, loose or worn in its grooves. An idler pulley and the tensioner's pulley are as a rule turned by hand and have to run smoothly and quietly, without roughness, play or wobble; the pulleys of driven units feel different according to the unit, and an alternator's freewheel pulley, if it has one, and a pulley with a clutch or a damper are judged only by the check the procedure gives. Do not turn the crankshaft pulley for this.
10. Where the drive has a tensioner, check it as the vehicle manufacturer describes: its arm has to move smoothly against its force and return without sticking, it may not be cracked or loose, and a hydraulic damper, if it has one, may not be leaking. Check as the vehicle manufacturer describes whether the pulleys stand in one line, using the lamp.
11. Look for the source of any oil, coolant or other fluid on the old belt or the pulleys. A leak has to be put right before the new belt is fitted, since fluid ruins a belt. Wipe the grooves of every pulley with a dry, clean cloth and remove dirt and belt residue from them with the soft brush. Do not use a belt spray or dressing on the pulleys or the belt.

Do not fit the new belt if a pulley turns roughly, has play or is damaged, if the tensioner sticks, is weak, leaks or is loose, if the pulleys are out of line, or if fluid still reaches the belt drive. Have the faulty part replaced or the leak repaired first; otherwise the new belt can fail or come off.

Fit the new belt

1. Check the new belt against the part number listed for the vehicle and compare it with the old one, as described under Choose the right belt. Look at the new belt: do not fit one that is damaged, kinked or soiled with fluid. Do not kink a belt, fold it tightly or turn it inside out.
2. Where the drive has a tensioner or is tensioned by hand: lay the belt around the pulleys as the vehicle manufacturer's routing shows, in the order and ending at the pulley the procedure gives. An elastic belt is positioned and fitted only as described in the step for it below. If the procedure does not give the order, find it out from the vehicle manufacturer's information before you fit the belt. The ribbed side runs in the grooved pulleys and the back on the smooth ones; a double-sided belt runs as the routing shows.
3. Check at every grooved pulley that all ribs sit in the grooves and that the belt is not offset by a rib to one side. Use the lamp and the mirror for pulleys you cannot see directly, and keep your fingers away from the edges of the pulleys.
4. Where the engine has an automatic tensioner: if it is not locked, turn or push it back against its force with its tool. Slide the belt over the last pulley. Then let the tensioner come onto the belt slowly under control; a tensioner that was locked is first held against its force with its tool, and its locking pin is withdrawn only at the point the vehicle manufacturer's procedure gives, as a rule once the belt lies on every pulley. Never let it snap onto the belt. Take the tool off.
5. Where the tensioner has marks or an indicator that show its working range, check that it rests within that range with the new belt, as the vehicle manufacturer describes. A tensioner that rests outside it means a wrong belt, a wrong routing or a faulty tensioner: find the cause before you go on.
6. Where the belt is tensioned by hand: set the tension by the method the vehicle manufacturer gives and to its specification, with the measuring instrument the procedure names, and tighten the fixings in the order and according to the specification it gives, with a torque wrench. Do not judge the tension by feel: a belt that is too slack slips, and one that is too tight damages the bearings of the units. Carry out any check or readjustment the procedure requires after the engine has run.
7. Where the engine has an elastic belt: fit it only with the fitting tool intended for that belt and engine and exactly as the instructions of the tool, the belt and the vehicle manufacturer describe. As a rule the engine is turned by hand at the crankshaft in its direction of rotation so that the tool guides the belt onto the pulley. Do not stretch the belt on by any other means, and do not refit an elastic belt that has been removed unless the vehicle manufacturer's instructions permit it.
8. Where an outer belt was removed, fit it now in the same way, each step according to its own tensioning: a new belt, or, where the vehicle manufacturer permits refitting and the belt is sound, the marked belt running in its former direction. Check the routing of each belt against your record and the manufacturer's routing once more, and the seating of the ribs at every pulley. Where the vehicle manufacturer's procedure provides for it, turn the engine by hand at the crankshaft in its normal direction of rotation as that procedure describes, with the tool it names, and check the seating again. Turn the engine only in the direction and in the way that procedure gives.
9. Remove every tool, including a locking pin, a fitting tool and anything used to turn the engine, and account for each of them and for every cloth. Refit the parts removed for access with their fixings as the vehicle manufacturer describes and tighten them according to the specification; where a wheel was removed, fit it and tighten its fixings as the manufacturer specifies. Lower the vehicle if it was raised.

A belt that is offset by a rib, routed wrongly or left with a tool in the drive can come off or tear as soon as the engine starts. Do not start the engine until the routing and the seating have been checked at every pulley and every tool is out of the engine compartment.

Check your work

1. Reconnect the battery if you disconnected it, as the vehicle manufacturer describes. Start the engine only in the open air, with the parking brake applied and the transmission in neutral or in the park position. Before you start it, make sure that nobody is near the belt drive and that hands, clothing, hair, tools and cloths are clear of belts, pulleys and fans.
2. Let the engine idle and watch the belt drive from a safe distance, without leaning over it: the belt has to run centrally on every pulley without fluttering, wandering or noise. Where the drive has a tensioner, its arm may not swing strongly. Check that the battery or charging warning goes out once the engine runs. If a warning is lit that was not lit before the job, find its cause as the vehicle manufacturer's information describes before you drive.
3. If the belt squeals, wanders or flutters, or a warning stays on, switch off the engine at once. Secure it against starting and let it cool before you touch the belt drive, and find the cause: the routing, the seating of the ribs, the tension, the tensioner and the pulleys. Do not drive until it has been put right.
4. Switch off the engine, secure it against starting and let the parts around the belt cool. Look at the belt once more: it must still sit in every groove with all its ribs, and a tensioner with marks must still rest within its range.
5. Before you drive, check with the vehicle standing that the steering assistance works normally, where the belt drives its pump; if it does not, do not drive, and have the vehicle checked. Check the other units the belt drives as far as your vehicle has them: that the air conditioning switches on without noise from the belt, and that the coolant temperature stays normal on the first drive. If something is not right, stop, switch off the engine and have the vehicle checked by a workshop.
6. Where the vehicle manufacturer's procedure requires the tension of a belt tensioned by hand to be checked again after a period of running, do that as the procedure describes, with the engine stopped, secured and cooled.

Mistakes to avoid

• Working on the belt drive with an engine that can start
• Slackening the belt without having recorded its routing
• Letting a tensioner snap back, or turning it in the wrong direction against its stop
• Levering a belt on or off with a screwdriver
• Stretching an elastic belt onto the pulleys without its fitting tool
• Fitting the belt offset by a rib on a pulley
• Routing the belt around the wrong side of a pulley
• Fitting a new belt onto a seized pulley, a weak tensioner or a drive that is contaminated by a leak
• Judging the tension of a belt tensioned by hand by feel
• Fitting a belt of another length or number of ribs because it can be got on
• Using a belt spray to silence a noisy belt
• Leaving a locking pin, a tool or a cloth in the belt drive
• Driving on with a damaged belt