How well do you know what's under your car's hood? While most people know the engine is the heart of the car, the average person doesn't understand many of its individual parts or how to change them. This leads to surprise when a vehicle suddenly doesn't start, which can happen if your timing belt needs replacing. Maintaining your timing belt is a critical element of car maintenance.
If your timing belt needs to be replaced, expect to spend $350 to $450. The procedure itself is relatively quick, but many mechanics perform other repairs or maintenance simultaneously. Prepare to wait around a few hours at an auto body shop for repairs to be completed.
Your timing belt replacement costs can increase if you have other repairs or replacements at the same time. Many auto technicians suggest replacing other engine components attached to the belt - such as the tensioner - at the same time as your timing belt. In other cases, the steps necessary to access components like the water pump coincide with the ones needed to replace the belt. The additional parts and labor can push the cost to $1,000 or more.
It's best to consider timing belt replacements as a preventative measure rather than a reactive one. If you wait until the engine fails to replace the belt, the additional damage your car suffers could cost you exponentially more.
What Does the Timing Belt Do?
The timing belt looks simple, but it's an essential component that keeps your engine functioning. It connects the crankshaft to the camshaft and makes sure they each rotate at the correct time. This ensures the engine valves open and close correctly. In most engines, the crankshaft turns at half the speed of the camshaft. The timing belt also connects to the water pump, injection pump, oil pump and more, depending on your car.
Curved teeth on a timing belt cause less friction than trapezoidal teeth.
Originally, the teeth on timing belts were trapezoidal in shape. Manufacturers started using curved teeth, which created less friction than the trapezoidal ones and thus generated less heat, in the 1980s.
There are other ways the camshaft and crankshaft can connect to each other. One, the two-gear method, is where gears on each engine part mesh directly with each other. The two-gear method is mainly used on trucks and large equipment.
Another option is timing chains. These last longer than rubber belts - up to 100,000 miles compared to a belt's 60,000. They're less sensitive to heat and general wear and tear. However, they are more expensive to replace.
Timing Belts and Modern Cars
Originally, cars had timing chains instead of belts. This option was incredibly noisy, however, so many manufacturers switched to belts. These were popular up to the 1990s, when automakers began designing quieter, more efficient chains.
However, there are many manufacturers that still use belts over chains. Timing belts are cheaper, lighter, easier to install and still slightly less noisy. In addition, timing belts allow for the camshaft and crankshaft to sit farther away from each other. The two must be relatively close for a timing chain to function properly, and they have to be right next to each other for the two-gear method. It's important to know whether your car has a belt, chain or other alternative so you're prepared for the proper maintenance.
Timing belts don't get stretched out over time, but they become brittle.
The Makeup of Timing Belts
Many people mistakenly believe that timing belts wear because they get stretched out over time. In actuality, the rubber belts are reinforced with fiberglass strands to prevent them from stretching. Instead, they simply become brittle after passing through the engine multiple times.
Obvious Signs of Timing Belt Damage
There are a few visual signs that your timing belt is in need of immediate replacement:
- Missing bits of rubber
- Damaged teeth
- Frayed or exposed cords
Even if your timing belt looks fine, you should replace it after the recommended mileage or number of years. The quality of a used timing belt can't be determined by appearance alone.
Additional Threats to Your Timing Belt
- Heat reduces your timing belt's durability. Be careful when driving in hot weather at high speeds.
- Oil and antifreeze can degrade the belt's rubber.
- Over-tightened belts are noisy and also generate heat. Many repair professionals replace the tensioner with every job.
For interference engines, the camshaft stops turning if the timing belt snaps.
Damage to the Engine
How your engine performs in the event of a snapped timing belt depends on its type. If you have an interference engine, the camshaft stops turning if the belt snaps. This leaves some valves open. The crankshaft continues to rotate, however, and the engine's pistons then hit the open valves, bending or breaking them. This can also result in damaged pistons or a destroyed cylinder head and block. Overall, a failed timing belt in an interference engine can result in several thousand dollars worth of repairs.
Noninterference engines, also called free-wheeling engines, incur less damage if the timing belt breaks. Both engine types will stall, however, leaving the driver stranded.
Signs Your Timing Belt Needs Replacing
Each manufacturer has a suggested time or mileage at which point your timing belt should be replaced. It's best to stick as close to this schedule as possible. There are other signs to look out for, however. These include:
- Your engine fails suddenly.
- A warning light on your dashboard comes on. If this happens, take your car to a mechanic as soon as possible. It could be that your timing belt is worn down, signaling the camshaft or crankshaft sensors to trigger your car's "Check Engine" light.
- You hear a scraping or slapping noise from the engine. This could mean your timing belt is loose or worn down. If it's loose, a simple readjustment can solve the problem, but you should replace the timing belt if it's worn down.
Do-It-Yourself Timing Belt Maintenance
Replacing the Timing Belt Yourself
Because the timing belt is such an essential part of your engine, you should only replace it yourself if you're absolutely sure you know what you're doing. In addition, you should already have the required parts and tools on hand. The parts themselves are expensive, and the tools aren't often found in a standard toolbox.
Even the slightest mistake could cost thousands of dollars in repairs to your engine. You might save money on labor for a quick fix, but you could pay even more down the road.
If you're sure you know how to replace a timing belt correctly, here are a few things to keep in mind:
- Never force a rubber belt around the pulleys by attempting to stretch it. This can damage the belt.
- Make sure everything is properly aligned and installed. Misalignment is one of the most common timing belt replacement errors.
- If you have to install sprockets, don't hammer them directly.
- Don't forget to replace the timing belt cover to protect the area from debris and grease.
The timing belt tensioner ensures your belt is under the right amount of stress.
The timing belt tensioner ensures your belt is under the right amount of stress to properly time the camshaft and crankshaft. Current cars have an automatic tensioner, while some older models have an adjustable one. Adjustable tensioners must be reset if the belt gets loose.
It's a little complicated to adjust the tensioner correctly yourself, and doing it wrong can have drastic consequences. If you don't feel comfortable with this bit of do-it-yourself work, feel free to contact a professional.
- To adjust the tensioner, refer to your owner's manual to find the location and correct course of the timing belt.
- Park your car on a flat surface, turn off the ignition and put on protective eyewear. Lift and prop the hood open, then detach the battery cables.
- Find the timing belt and remove its cover.
- Loosen the bolts securing the tensioner with a wrench, and then loosen the tensioner so it lightly touches the timing belt.
- Make sure the timing belt is properly aligned, checking to see if the marks are coordinated with those on the camshaft, crankshaft and sprockets. If they're not, or if the belt is somehow following the wrong course, your owner's manual details how this setup should look.
- Use a wrench to move the crankshaft's pulley, turning the engine two or three times. See if the timing belt shows any resistance and look to make sure the vales and pistons don't touch.
- Resecure the tensioner bolts, taking care not to over-tighten them, then reattach the timing belt cover.
- Attach the cables back to the battery, then close the car hood.
- Start the engine and ensure everything runs properly.
Additional Factors to Consider
Engine Components Connected to the Timing Belt
The timing belt connects various components of the engine, depending on your vehicle.
- The crankshaft converts linear energy to rotational energy, allowing the wheels to move.
- The camshaft is a rotating cylinder with multiple lobes designed to open the intake and exhaust valves as the camshaft turns.
- The water pump circulates water and coolant throughout the cooling system - without it, your engine will overheat.
- The oil pump helps lubricate and cool necessary parts of the engine.
- The injection pump helps drive fuel to the engine.
History of the Timing Belt
The first timing belts were used in sewing machines to synchronize the needle and bobbin drives. These belts had metal clips, but the sound they made was practically unbearable. In 1945, sewing machine manufacturer Singer solved the noise problem by using a rubber belt with trapezoidal teeth instead.
A German auto company named GLAS was the first manufacturer to use timing belts in the mass production of cars. Soon, other automakers followed suit.