A vehicle's timing chain connects the crankshaft to the camshaft. This is a fundamental element of the engine which, when working correctly, allows the valves to open and close in accordance with precise intervals based on the position of the pistons. In this way, the best performance of the engine is guaranteed. Over time, the timing chain wears out and can affect engine operation. Sooner or later it may need to be replaced; however, with the right tools, a maintenance manual and some mechanical knowledge, you can do the repair yourself. However, be aware that this is an important intervention and could cause serious consequences if you do not proceed correctly.
Steps
Part 1 of 8: Preparing for Engine Work
Step 1. Find your vehicle's user and maintenance manual
Most likely, you will have to disassemble and reassemble several components. Also, you need to make sure your car is equipped with a timing chain and not a belt. These two parts perform the same function, but the process of replacing them is quite different. This article describes only the process for changing the chain.
Step 2. Before proceeding, clean the engine thoroughly using a degreaser
If the engine is clean, you can more easily identify worn or leaking components. In addition, the work will proceed without too much mess. Do not clean or perform any work on the engine while it is still very hot.
Remember that the degreaser and oil you remove from the engine during rinsing could kill lawn grass and are highly polluting. You should perform these operations in an area where there is an adequate drainage path equipped with a chemical filter
Step 3. Determine the firing order of your car
This information could be engraved directly on the engine body (on the cylinder head, valve covers or manifold) or reported in the maintenance manual among the various specifications. You can also get a service manual (the one that specialized mechanics use) to determine this order. This is essential information, because you will need it later to check the first cylinder (the one that activates first in the firing order).
Step 4. Disconnect the battery cables
You should not perform any maintenance work on the engine with the electrical supply connected. First, disconnect the ground wire (the negative one) and then remove the positive one.
Part 2 of 8: Unplug the radiator
Step 1. Remove the radiator cap
This way, you can drain the coolant from the system.
Step 2. Open the coolant drain valve
It is located at the bottom of the radiator and consists of a plastic screw or a pressure cap that you can easily open. Coolant is a mixture of water and antifreeze, it is very toxic and should be stored in a plastic container with a screw cap. The ideal container would be an old bottle of antifreeze.
Step 3. Disconnect the radiator hoses
Find the hoses that extend from the radiator to the rear of the engine. Squeeze the clamps with pliers and slide them back along the tubes. Then, move them to loosen them and detach them permanently from their seat.
There is no need to disassemble the radiator. It is necessary to loosen the pipes and drain the coolant to remove the water pump in the next step
Part 3 of 8: Remove the Drive Belt Components
Step 1. Locate the timing diagram
Typically, it is listed under the hood of the car or in the specific manual for the drive belt. If your car is very old, it may be equipped with a poly V-belt. Either way, if you can't find the timing diagram, you should take a photo or sketch of the engine before removing the belt.
Step 2. Release the tension on the belt
If it is a modern belt, simply compress the belt tensioner spring. Some of these elements can be crushed with a simple tool, such as a wrench, while others need a special tool. Poly V-belts can be removed by adjusting the position of one of the pulleys to release tension.
Step 3. Remove the belt
Once it is no longer under tension, this component should slide off the pulleys without resistance.
Step 4. Remove the heating pipes from the water pump
If your machine has heating pipes connected to the pump, loosen the hose clamps with a screwdriver and slide them along the pipes. Then loosen the tubes and pull them to detach them from the pump.
Step 5. Remove the water pump
Remove all the bolts that secure it to the engine; typically, there are three or five. When each bolt / nut has been unscrewed, simply lift the pump with your hands.
Step 6. Remove the crankshaft pulley (harmonic balancer)
Remove the bolt and gasket located in the center of the pulley itself; afterwards, partially reinsert the bolt into its hole and use a special extractor tool. This should not be equipped with clamps or pliers, but should exert its force in the center of the element. By doing so, you protect the rubber ring of the harmonic balancer.
Part 4 of 8: Remove the Timing Chain
Step 1. Remove the cover from the timing chain
Unscrew it from the engine block. Pay attention to the fact that the bolts have different lengths and an insertion criterion that you must remember when you have to reassemble the cover. The best thing to do is to put each one back into its own hole in the cover, once the cover is set aside.
Step 2. Locate the notches on the crankshaft and camshaft gears
These toothed discs are connected by the timing chain, so that the position of the pistons (in turn connected to the crankshaft) is synchronized with the fuel and exhaust valves, which are managed by the camshaft. All this guarantees the perfect functioning of the engine. Each gear should have reference marks for the correct position.
Step 3. Find the notches or shiny links in the timing chain
These links are shinier than the others and are used to align the motor.
Step 4. Put the engine in top dead center
To do this, align the shiny links of the timing chain with the notches found on the camshaft and crankshaft gears. Remember that the crankshaft must be in dead center during both the compression and exhaust times of the piston. The top dead center must coincide with the compression.
Step 5. Remove the timing chain
To do this, you can loosen the tension gear with a wrench or socket. Afterward, you can slide the chain off the gears.
Part 5 of 8: Install the New Timing Chain
Step 1. Lubricate the gear before inserting the new chain
Use some transmission oil to make sure the chain and sprocket are working their best for the longest time possible.
Step 2. Place the new chain on the gears, respecting the alignments of the notches
You need to make sure that the shiny links of the chain line up vertically exactly with the notches on the sprockets, in the same position where the old chain was mounted. By doing this, you can find the top dead center, should it be necessary.
Step 3. Tighten the chain according to the specifications in the manual
Some are tensioned by adjusting the crankshaft or camshaft gear, while others have an automatic chain tensioner. This step varies by vehicle model; the important thing is to make sure that the chain is as taut as possible.
Part 6 of 8: Replace the Crankshaft Seal
Step 1. Remove the crankshaft seal with a hammer and awl
This is a rubber gasket that surrounds the crankshaft and the timing cover.
Step 2. Tap the new gasket into the timing cover
You need to make sure it is in the correct position, as it will seal the timing compartment when you bolt the cover back to the engine.
Step 3. Grease the gasket with a little oil
This detail is necessary to guarantee the perfect seal of the seal.
Step 4. Refit the timing chain cover
The bolts vary in length, remember how you disassembled them and make sure each is in the correct housing.
Part 7 of 8: Reassemble the Drive Belt Components and Cooling System
Step 1. Screw on the harmonic balancer
In this case, there is only one bolt in the center of the pulley that holds it in place. Consult the maintenance manual or the specific mechanics manual to know the exact tightening torque.
Step 2. Reinstall the water pump
Replace the bolts that secure it to the engine block.
Step 3. Hook the heating pipes to the pump
If you have previously disconnected these hoses from the water pump, you need to slide them into place; later, you can secure them in place by tightening the appropriate clamps with a pair of pliers. If the zip ties have a locking screw, use a screwdriver to tighten them. This way, you can be sure that the hoses do not come off the pump.
Step 4. Put the radiator hoses back in place
If the ones at the bottom of the radiator are still detached for some reason or you have disconnected the top one, now is the time to return them to their original positions. Once inserted into the radiator, use a pair of pliers to move the safety ties right to the junction point. In this way, the tubes are well secured in place.
Step 5. Fill the radiator with coolant according to your car's specifications
If the old one looks dirty or is over a year old, you should replace it with new antifreeze. Remember to dilute it according to the instructions in the manual and fill the appropriate tank up to the maximum mark shown on the walls of the tank itself. If, on the other hand, the old coolant is clean and relatively new, you can transfer it back to the system.
Step 6. Activate the drive belt
You should follow the timing diagram printed on the hood or in the maintenance manual to make sure the belt is operating correctly. The pulleys with the notches must be coupled to the notched side of the belt, while the flat ones must be driven on the smooth side.
Step 7. Tension the belt
If it is a modern belt, you can operate the chain tensioner; if you are working with a poly V belt, you will need to manually tighten it. As a general rule, the chain should have a maximum play of 12mm at the center point of the longest segment. Read the maintenance manual for more details; if in doubt, ask an experienced mechanic.
Step 8. Check one last time that all belts and hoses are connected
You do not have to start the engine unless you are sure that all the elements are well fitted. Take a moment to go through the entire engine compartment and make sure every component is in place before proceeding.
Part 8 of 8: Completing the Job
Step 1. Plug the battery back in
First, mount the positive cable and then the negative one.
Step 2. Start the engine
Turn the key and start the vehicle.
Step 3. Inspect the engine compartment for leaks and drips
Look under the hood and under the car itself, to make sure there are no traces of liquid. If you notice a coolant leak, check that all hoses are securely attached to the radiator and water pump. If the liquid is oil, you will need to replace the crankshaft seal again.
Step 4. Check the timing with a strobe gun
This way, you are sure that all cylinders are firing at the right times, that the valves open and close with the correct rhythm in relation to the position of the piston.
Advice
When the engine idles with difficulty or sluggishly, there are backfires, the vehicle performance changes or you hear a noise coming from the front of the engine, there could be problems with the timing chain
Warnings
- Always pay close attention to hot engine parts, sharp edges or hazardous materials; take the necessary precautions.
- Always work on a level surface and support the vehicle with jacks. Do not service the car after parking it on a soft surface.
- Make sure you have all the right tools for the job, to avoid injuries caused by improper tools that lose their grip or break.
- Never leave radiator coolant in an open, unattended container. Collect and dispose of it properly. If you do not know how to do it, call the technical office of your municipality or ask the staff of the ecological island for more information.
- Do not attempt this type of repair if you have no mechanical knowledge. This is a complex job involving vital parts of the vehicle. Even a small insignificant mistake could cause serious damage, requiring expensive repairs or even the replacement of the entire engine.
