Timing chain: when to change and how to do it?
Despite the growing popularity of timing belt engines, chain motors are still to be found. Moreover, it can be seen on such cars as Mercedes, Honda, Nissan, Volkswagen, Audi and Skoda. Timing chain performs the same function as the belt - actuates the camshaft, which, in turn, opens and closes the valve in time. Some believe that this mechanism is designed for the entire lifetime. But it is not. In today's article, we will learn when to change the timing chain and how this procedure is performed.
In many manuals, it does not mean how much to replace this element. But as practice shows, the drive resource ranges from 100 to 200 thousand kilometers.
Yes, the timing chain will be more reliable than a belt, and it does not break, but only stretches. But it is worth remembering that this stretching is compensated by the tensioner only up to a certain point.If the chain is lengthened, this is not a reason for an urgent replacement. But if you drive it for a long time, it is possible to shift the valve timing. After all, the tensioner will no longer be able to compensate for the length over which the element stretched.
An interesting fact: the resource chains on the engines of "Honda" (in particular, "Civic") can reach up to 250 thousand kilometers. However, no signs of replacement are observed.
First of all, you can learn about the upcoming replacement by computer diagnostics. So, during this operation, you can accurately determine the violation of valve timing. Another indirect sign of stretching is increased fuel consumption. With run the chain can make the raised noise in work. But it is worth remembering that these sounds can be short-lived. If the noise is only when you start the engine, this is normal. The oil pump simply did not have time to generate the necessary pressure.
Also note that if the chain has jumped, the motor will “walk” from side to side and unstable to work at idle. These are the main signs, the appearance of which is worth inspecting the state of the chain. However, experts advise not to bring the car to such a state.It is better to replace the item by mileage - once in 150 thousand on average. Also, it is desirable to make a replacement when buying a used car. Not every owner will be engaged in such a business before the sale, because the chain does not issue any particular signs of partial stretching.
You need to understand that to perform such an operation as replacing the timing chain, you need not only this element. Also, with the run, the shoes of the damper and tensioner wear out.
Therefore, it is worth buying items only in a set. Only this way you will be sure that after replacing the chain will last a long time. As for manufacturers, it is better to choose the original. Change the timing chain on the "Nissan" (as well as on any other car) is not easy. And to disassemble the engine every 20 thousand kilometers hardly anyone will like it. Therefore, you should buy only high-quality original kits or a good analogue in the absence of the first option. If we talk about the price of a foreign car, this set will cost from 3 to 8 thousand rubles on average.
What else do you need?
Since we will work with the timing mechanism, it is desirable to have a viewing pit. You should also prepare the following set of tools:
- Face heads.
- A piece of clean cloth.
- Flat screwdriver.
- Wooden block.
- Torque and adjustable wrench.
- Containers for draining process liquids.
First of all, we need to remove the connected ignition cables to the coil. Next, unscrew the coils themselves with a key wrench and set them aside. It is important to sign each of them in order not to be confused during assembly (otherwise the machine simply will not start). Next, disconnect the air pipe from the valve cover. The latter is attached to the head with a few bolts. The cover must also be removed. Next, dismantle the right engine mount (optional, depending on the design features of the car). After that, prepare the container to drain the oil and unscrew the cap in the crankcase. Also dismantle the oil filter. After that, drain the coolant. If it is relatively new, it is important that the container is clean (the same applies to oil). Substitute the container under the drain hole and open the faucet.
When there are no more technical fluids in the system, remove the radiator and remove the alternator belt.Then remove the hose clamp. In the next step, dismantle the head of the block. The cover is usually fixed on four bolts. Also remove the oil pan. On some cars for this you will first need to remove the front exhaust pipe. After that, loosen the bolts of the water pump pulley. So we remove the drive belts that go to the air conditioning and other attachments.
Next we need to find a place between the crankshaft and the side of the engine crankcase. Here we place a wooden bar and unscrew the shaft pulley. To do this, you should apply the end head of a large exchange (usually 27 or 30).
The next step is to remove the pump pulley. Under it is a gasket - it also needs to be removed. Additionally remove the oil pump. Turn off the camshaft gear. They are mounted on bolts. The shaft itself is also removed using an adjustable wrench.
So, we have released access to the chain and now we can proceed to dismantle it. To do this, remove the damper in the upper part, the bar that is responsible for the tension of the damper, and hydraulic tensioner.After that, take the lower bar and put it on her hairpin. Next, remove the old timing chain. With the help of a flat screwdriver, get rid of the gear that is below.
Now you can compare the length of the old chain with a new one. Usually it stretches about 2-3 centimeters. This is a very serious indicator. How to install a new chain? It should be placed in place of the old in the same way and additionally lubricated with engine oil. After removing all the dirt from the side of the engine, moisten a clean cloth in a degreaser. Also, it should go in those places where sealant was previously detected. It must be carefully scraped off and put a new one.
Pay attention to the timing chain marks. The element must be installed so that the tags match on the pulleys and on the chain itself. After that, you can proceed to the assembly of all attachments and components. Pay special attention to the head of the block.
It is tightened in a special pattern, criss-cross, while respecting the torque. The exact time of all cars is different, and this can be found in the instruction manual. In places where gaskets were installed, you need to put new ones.Old sealing elements can not be used - they have shrunk and will be ineffective.
Chain or belt?
Timing cars, as we said earlier, can have two types of drive. This is a chain or belt. It is clear that if you have an engine with a timing chain, you should not put the belt in any case. But what if there is a choice between two cars? There is no unequivocal answer to the question “what’s better”. Both drive elements have their pros and cons. Thus, the circuit is more reliable, because it never breaks and signals about the signs in advance. But at the same time it is noisy in work, and it is much more difficult to replace it than a belt. The latter, in turn, does not emit noise in the work.
But it has to be changed more often - every 60 thousand kilometers. In case of breakage, the bend of valves is inevitable. The only exceptions are the 8-valve engine. But today they are practically not produced.
So, we figured out when to change the timing chain and how to do it yourself. In total, the operation will take a full day light. To get the job done quickly, you need to prepare in advance all the new gaskets, stock up with sealant and tools.Please note that if the head of the block is incorrectly tightened, it is possible that the gasket burns out and deformation of the cylinder head itself.