Timing Belt is a notched belt, made of rubber that enables the crankshaft to turn the camshaft, and opens and closes the engine valves synchronously with the pistons. In late model vehicles, the timing belt has essentially replaced the metal timing chain. It is also called a camshaft drive belt or a Gilmer belt.
Timing belts help your vehicle’s engine to operate. They connect your engine’s crankshaft to the camshaft and also play a vital role in controlling the pistons as well as valves in your vehicle.
Simply explained, the timing belt is a reinforced rubber band with teeth or notches on the inner side that precisely synchronize the opening as well as the closing of the engine’s valves. As the crankshaft turns, it sets the timing belt in motion. The timing belt then turns the camshaft and opens or closes each of the valves and allows the pistons to move up and down. For instance, a four-stroke engine includes four phases: the intake phase, compression phase, combustion phase, and exhaust phase. In the intake phase, air, as well as, fuel get pulled into the cylinders. In this phase the intake valves are open and the exhaust ones are closed.
In the compression and combustion phases, the air and fuel are mixed, compressed, and then it is ignited by the spark plugs. During these two phases, all valves are closed. The final stage is the exhaust phase where the air and fuel that is present in the exhaust valve goes out. In this phase the exhaust valves are open and the intake ones are closed.
The timing belt controls the opening and closing of the valves as well as the timing of the pistons throughout each phase. The timing belt allows each of the step to take place in the precise order.
Symptoms of a Bad or Failing Timing Belt
1. Ticking noise coming from the engine
The timing belt is attached by way of a series of pulleys to the engine’s crank as well as camshaft. The crankshaft helps to power the engine’s connecting rods which are attached to pistons found inside the combustion chamber. The camshaft operates the cylinder head valves and rocker arm assembly, whose purpose is to send fuel into the combustion chamber and expel burnt gases out of the exhaust manifold. When the timing belt starts to wear out, it might create a ticking sound inside the motor. This warning sign can also be an indication of low oil pressure or the engine not having the proper amount of lubrication.
2. Engine won’t turn over
If the timing belt is broken, the engine can’t turn over or ignite. When you turn the key, you may hear the starter motor engage, but since the timing belt operates the crank and camshaft, it will not turn over. Obviously, if the car doesn’t start, calling a mechanic is usually the first step. However, if the issue is due to the timing belt being broken, it might also result in other internal engine compartment damage. In a lot of cases, the timing belt breaks while the engine is running. Some of the typical damage caused to a vehicle due to a broken timing belt consists of damage to cylinder head hardware (rocker arms, push rods or valves), damage to crank bearings or oil pump inside the oil pan.
3. Engine misfires
A worn out timing belt can also impact the engine’s fire rate. The timing belt is attached to pulleys that drive the crank and camshaft as we’ve indicated above. However, sometimes the belt can slip on the camshaft drive and cause one cylinder to open or close earlier than it is supposed to be. This might cause a misfire situation and if not replaced soon, it might result in catastrophic engine damage.
4. Oil leaking from the timing belt cover in front of the motor
It’s also obvious that the engine will leak motor oil from the timing belt cover. The cover is secured by a series of nuts and bolts that might become loose over a period of time. Another issue that will cause the oil to leak is when the gasket between the engine block and timing cover wears out, is cracked or has been improperly installed and is pinched. Leaking oil from the timing belt cover usually results in engine overheating as well and can premature wearing of the timing belt.
The following video shows How to tell if Your Car Needs a New Timing Belt-
How to Change a Timing Belt
Step 1- Disconnect the negative battery cable.
Make sure you have your radio security code (if equipped) or any preset radio stations on a piece of paper to allow for quick resetting once repairs are made.
Step 2- Remove the alternator belt.
Depending on your model, you might need to remove the serpentine belt to get to the timing belt. Loosen the nuts and push the alternator if necessary to create slack on the belt and remove it.
Step 3- Remove accessories like the power steering pump, alternator, and air conditioning compressor so you can access the timing belt cover.
Do not remove pressurized fittings from the air conditioning compressor, most can be unbolted and pushed out of the way without even discharging the system. Remove the valve cover assembly to access the timing belt.
Step 4- Remove the distributor cap if your vehicle is equipped with one.
• You might have to pry apart the retaining clips to free the distributor cap, as well as remove any screws holding the cap in place.
• Some modern cars with electronic ignitions don’t have any distributor. They contain a cam and crankshaft position sensor instead. The main purpose is to determine Top Dead Center (TDC) on the first cylinder. Consult the engine repair manual as these will differ by model.
Step 5- Line up the timing marks.
• With a wrench or socket on the crankshaft bolt rotate the engine until the timing mark on the crankshaft pulley is aligned with the 0° mark on the timing scale.
• Verify the distributor rotor is aligned with the index mark on the distributor housing indicating the rotor is in position in order to fire the number one cylinder. If not, just rotate the engine again.
• Don’t interfere with engines until and unless you’re sure the belt is still intact. If you still have not bent your valves with a broken timing belt, you will likely do so if you spin the crankshaft without the camshaft being spun.
Step 6- Determine if the harmonic balancer pulley has to be removed for removing the timing belt cover.
Usually, the cover saddles over the end of the crankshaft, and this pulley will not allow you to remove the cover without first removing it. Note that an additional seal will be required to reinstall it if this is the case and special crankshaft pulley and gear removal alignment tools may be needed.
Step 7- Remove the bolts or screws holding the timing cover in place.
Remove this cover from the engine. Some engines consist of a two-piece timing cover. Remove any components or accessory drive belts that are interfering with removing the timing belt cover. This varies by model; consult your service manual for determining which parts need to be removed from your vehicle.
Step 8-Check for proper alignment of the crank and camshaft timing marks.
• Many engines consist of a dot or index line on the pulleys and/or sprockets that must be lined up with corresponding marks on the block, cylinder head, or accessory shaft. On some of the engines, the index mark on the camshaft sprocket aligns with the parting line of the first camshaft-bearing tower.
• This is very crucial if you’re replacing a timing belt that has broken. Consult your service manual for the correct alignment procedure of your vehicle and correct any misalignment before installing the new timing belt. These marks might also be displayed on a label on the timing belt cover on some engines.
Step 9- Check the area around the belt for signs of oil leakage.
Look around the camshaft, crankshaft seals, valve cover as well as the oil pan. Just check for any coolant leak from the water pump and water pump by-pass hose. Leaks need to be repaired before the new belt is installed.
Step 1- Loosen the mounting bolt(s) that hold the belt tensioner using any special cam holding tools, while following the service manual.
Do not remove the tensioner completely until and unless you are replacing it. Instead, pivot the spring-loaded tensioner away from the belt and then just retighten the mounting bolt(s) to hold the tensioner in the loose position.
Step 2- Examine the tensioner pulley for any damage such as dents or cracks.
• Spin the tensioner pulley and listen for a rattle or humming noise that will indicate loose or worn bearings. Uneven wear at the rear of the old timing belt can indicate a misalignment between the tension pulley and timing belt due to worn bearings.
• If there are any indications of damage or worn bearings are found, replace the tensioner pulley. The permanently lubricated tensioner pulley bearing can become dry, worn, loose, broken or can freeze up, so the best practice is to replace it if it’s not new.
Step 1- Slide the belt off the sprockets.
With the tension on the timing belt relieved, the belt needs to slide easily off the sprockets. Timing belts that have been used for a long time might stick in the pulley grooves and require some gentle prying with a screwdriver to get released. Inspect the timing belt pulleys and water pump for any replacement before proceeding to install the new belt.
Step 2- Replace with a new belt and reassemble.
• Torque the timing belt to the proper specifications and pay special attention to “torquing” specs on the engine manual, particularly the crankshaft pulley mounting bolt which usually has a very high torque spec.
• If the car is equipped with a hydraulic timing belt tensioner, its removal might be required to compress the piston back into the cylinder after a ratchet is released. Place it into a vise and compress until and unless holes line up to allow the insertion of a holding pin. Once the pin is in place, the tensioner can be re-installed when the belt is installed with the pin pulled in order to allow the tensioner to place tension onto the timing belt.