When You Should Replace Your Timing Belt

A timing belt is a toothed belt made from reinforced rubber that rides on sprocket wheels. It’s driven by the engine’s crankshaft pulley and provides rotational force for camshafts that open and close the intake and exhaust valves at exactly the correct time for smooth combustion. The valves must work in coordination with the operation of the engine’s intake, compression, combustion, and exhaust. The timing belt makes sure this all comes together. We will go over how timing belts wear out and why it’s very important to replace them when they start wearing out.

Timing belts replaced timing chains on smaller displacement engines in the 1970s and 1980s because they weighed less and were not as expensive to produce. That said, vehicles with larger displacement engines still use timing chains because they require more strength to spin the massive camshafts that operate a large number of valves.

Also, a timing chain lasts a much longer period of time than a timing belt. In many cases, chains will last the entire lifetime of the vehicle.

Moving on to timing belts. Over the first 20 to 30 years of their existence, manufacturers usually recommend replacing them between 45,000 and 60,000 miles. There are manufacturers that suggest replacing these belts every 30,000 miles. Over time, rubber compounds have become more durable making replacements up to 100,000 miles or even more.

The Importance Of A Timing Belt

Because they are made from rubber, the timing belt will eventually dry up, harden, crack, and come apart. If the timing belt breaks, your engine will immediately stop operating because the intake and exhaust valves will come to a complete halt causing compression in the cylinders to disappear. When valves stop moving simultaneously with the rest of the engine, you will end up with bigger issues than a stalled engine.

Damage to the valves and cylinder heads that house them can result if your engine has what is known as an “interference” design. With an interference motor, both the intake and exhaust valves will extend further into the cylinder area when they are opened. This is an engineering call that’s done for performance or emission reasons. During normal operations, timing means the pistons are never trying to take over the same space as the valves. If the valves come to a complete halt too far into the cylinder heads, the pistons will smash into them before coming to a halt.

In one case, the 4-cylinder engine, pistons, and valves were colliding and then destroyed when the timing belt broke. The engine had to be completely rebuilt.

Permanent damage to the valves along with the bearings and other components will take place. In other cases, the pistons and cylinder heads can become damaged by rods and valves pushing through the metal. Also, piston connecting rods have been known to push through oil pans after the crankshaft broke because of a violent shock.

Engines with a “non-interference” setup will not be affected by the piston and valve collision damage but you will end up stranded. If you do not know which kind of setup your engine has, call the vehicle’s manufacturer and find out.

Signs Of Wear

Timing belts are located behind the cover plate and are not exposed to destructive elements from inside the engine compartment. Unfortunately, that makes a visual inspection impossible. Also, because timing belts have teeth, if they are worn and slip, they will not make the traditional loud squealing noise that worn serpentine belts make. That said, a worn timing belt can create a slight ticking sound from behind the engine cover but that sound could be caused by other unrelated issues.

In order to see the condition of the timing belt, you have to remove the cover plate which essentially forms the very front of the engine. That means various accessory drive belts and other external components bolted to the front of the engine will have to come off first.

Without being able to see, hear, or feel signs of wear, it’s impossible to make a judgment call. You will have to replace the timing belt at the manufacturer’s recommended mileage. The exception might be for vehicles that are rarely driven. Rubber deteriorates over time so there will be cases when the timing belt replacement is justified after X number of years before the stated mileage interval is reached. Most manufacturers will cover it by saying “Replace the timing belt” every 100,000 miles or 10 years, whichever comes first”.

If you have purchased a used car and do not have any service records regarding the history of the timing belt replacement, your best bet is presuming the belt has not been changed on schedule. The labour to inspect a timing belt is about the same as replacing it. I’d go ahead and replace it unless an inspection shows the belt is brand new.

Signs There Are Issues

If you see oil leaking from the timing belt cover, probably a front engine seal is leaking or the front cover which is supposed to seal in oil has a leaking gasket. Whatever the cause, engine oil is extremely harmful to the rubber causing it to become soft and come apart. If the timing belt becomes damaged from oil, immediately replace it and find out where the leak is coming from.

Over time, the timing belt will become stretched as it ages. This can lead to the belt slipping a tooth on the pulley wheel. The engine will continue to run but the valve timing will probably be off just enough to cause misfiring. As RPMs increase, the engine may run a little rougher and spit out more smoke. On newer cars, the Check Engine light will probably come on.

Visible Belt Inspection Reveals Issues

If you are able to get the timing cover off and find oil on the belt, the leak must be fixed immediately and a new belt installed. Cracks on the belt or missing teeth are the most common signs the belt must be replaced.

The older the belt is, the more likely it will have dried rubber which can lead to teeth breaking off. Also, beware of cracks on the timing belt.

It’s really important to understand that the loss of rubber material can happen along all surfaces of the teeth during normal wear. Gradually, the rubber that has worn off will collect in between the teeth which in turn will dull the sharp edges and cause vibrations. A belt that’s lost rubber will not be as tightly held by the tensioners so it’s likely a tooth will slip out of its position.

The Best Time To Replace The Timing Belt

If you will be replacing the water pump, it will require removing the timing belt cover at the front of the engine. There is very little effort after that to slip a new belt in place once you get into the mechanisms. That said, removing the timing belt cover plate is the majority of the work due to the serpentine accessory drive belts and other external components that must be removed first. If you are replacing your timing belt at the recommended time, there will be minimal labour to replace the water pump because you have already done all the hard work, to begin with.

If replacing the water pump is your biggest concern, re-installing the old belt is not a good idea. Chances are, it has stretched just enough to make re-setting the camshaft timing a major challenge.

Pulley Wheels And Tensioner

We strongly suggest replacing the tensioner for the timing belt while you have access to it. Check the condition of any idler pulley wheels that are in place to help determined the belt’s path. All these items have bearings as well that will, over time, gradually wear down and should be replaced when the belt wears out. A damaged tensioner will create a sound and vibrations that can be heard if you listen closely to the front of the engine.

When you change the belt, it’s the perfect time to install a new timing belt tensioner.

There are definite signs that a timing belt tensioner or idler pulley wheel is worn and can no longer maintain the right alignment. A belt with frayed edges indicates that the wobbling of the pulleys is causing the belt to ride slightly awry. This wobbling and misalignment happens because mounting bolts that secure these items in place have become loose or the internal bearings have worn down to the point that they can not keep the pulley flush and level for needed support.

Belts that are worn are the result of pulley wheels or a tensioner having become misaligned due to wear.

Remove the timing belt and see if the tensioner and pulleys are tight or if they have side-to-side play so you can wiggle them excessively. Rotate the pulley wheels to see if they spin easily or if you can feel roughness as they turn. Anything that is not right should be replaced.

When you think about the cost of an engine rebuild, the price for a new timing belt, pulley wheels, and tensioner is only a few pennies in comparison. Skimping on these items is looking for disaster. Make smart financial decisions and replace these parts on schedule.

Summary

Like all the other major components that allow your vehicle to run smoothly and get you from point A to point B, the timing belt plays another critical part. Driven by the crankshaft pulley, the timing belt offers rotational force for the camshafts to open and close intake and exhaust valves at exactly the right time. The engine’s intake, compression, combustion and exhaust strokes all operate correctly thanks to the timing belt.

If you plan to inspect and replace the timing belt, it will not be a walk in the park. The timing belt is housed behind a cover plate that will take a good amount of effort to get into. If this is something you are not able to take care of, make sure you follow the manufacturer’s recommendations for changing the timing belt which should be in your operator’s manual.

When all else fails, take your vehicle to your mechanic and have whatever is wrong quickly fixed. It’s a matter of having a car broken down on the side of the road or a well-maintained piece of machinery that will be with you for a long time.

If you believe you may have a problem with your timing belt you can have it checked in and around Manchester city centre and North Manchester, Oldham, Bury, Bolton, Rochdale, Stalybridge etc. by Servicing Master. You can get a quick repair or service quote by using our simple car service quote form. We also offer a collection and drop off service. A convenient, friendly and affordable service, try Servicing Master once and you’ll never go back. Give us a call now on 0161 302 0201. Or simply book your car service now.