What is in timing chain engine oil? This is the real reason for the trouble.

People who have had a problem with a timing chain stretch have probably heard or read somewhere that it is related to changing the engine oil. If they understand mechanics, they know that it's not about lubricating the chain itself. So why?

Previously, the timing chain was so strong that it was almost impossible to replace it. In the best case, when repairing the main engine. Today it is a completely different design. In modern engines, the chains are much longer and stretched between several gears.. In addition, they are more distant from each other, because the camshafts located in the fuselage, i.e. close to the crankshaft, already history.

All this means that the chain must be correctly tensioned not only on the sprockets, but also between them. This role is performed by two types of elements - the so-called guides and tensioners. The skids stabilize the chain and tension it in the places of tension between the wheels., and tensioners (often one tensioner - marked with a red arrow in the photo) tighten the entire chain in one place through one of the shoes (in the photo the tensioner presses on the slider).

The timing chain tensioner is a relatively simple hydraulic component. (if mechanical, then do not read further, the article is about hydraulic). It works fully automatically based on the oil pressure generated in the system. The higher the pressure, the greater the voltage, the lower, the less. The chain must be tightened, for example, when the load on the engine increases, as well as when the chain or other elements are worn. The tensioner then compensates for wear on the timing components. There is one catch - it runs on the same oil that lubricates the engine.

The tensioner needs good oil.

The engine oil that enters the tensioner during the first stage of operation, after starting the engine, is relatively thick and cold. It doesn't have the right temperature yet, so it doesn't flow as well. After a while, when warming up, it does its job 100 percent. However, with oil consumption and contamination, the time between starting and proper operation of the oil, and hence the tensioner, increases. It lengthens even more when you pour too viscous oil into the engine. Or you change it too infrequently.

We got to the heart of the problem. Wrong tensioner this not only makes the chain too loose in the first minutes or minutes of operation, but also when the oil is too "thick" or dirty, the tensioner does not respond properly. As a result, an incorrectly tensioned timing chain destroys the interacting elements (sliders, gears). It's worse dirty oil may not reach an already dirty tensioner and this one will not work at all (change the voltage). The higher the wear of the mating elements, the more play, the chain wears out even more, until we reach the point where you hear ...

chain screen

It is impossible to check the condition of the timing chain drive in any non-invasive way without dismantling the entire housing and inspecting its components. Contrary to appearances, this is a big problem, but more on that later. More importantly, the noise coming from the timing case, which is not always picked up by a mechanic, let alone buying a used car, is a sign of wear on the timing chain drive. No noise, except for a loose timing chain. The faster the user response, the lower the potential costs. In many engines, it is enough to replace the tensioner and chain, in others a complete set of sleds, and in the third, in the most worn ones, gears still need to be replaced. It's even worse when it's gears with variable valve timing. This already means costs in the thousands of PLN just for spare parts.

It's such a big deal for this often timing chain engines are good engines. However, it is impossible to check this area without the involvement of a mechanic and a workshop. An example is Audi, BMW or Mercedes diesels with great durability. If everything is normal, then they are low-failure, powerful and economical. However, after buying a car with a stretched chain, but, for example, not yet noisy, it may turn out that in order to enjoy all the advantages of such a diesel engine, you need to spend PLN 3000-10000 on a timing belt replacement. .