The oil flows from under the valve cover. Oil leak - what to do

The lubrication system of an internal combustion engine is similar to the human circulatory system. Oil, like blood, circulates in a closed circle, lubricating, cooling and cleaning moving parts. All this, of course, occurs under a certain pressure, a reduction or excess of which will invariably lead to a disruption in the work process.

The slightest leakage of oil from the engine - a signal to the fact that there was a depressurization of the system. And this is a serious reason to think about the diagnosis of the power unit.

In this article, we will talk about what causes and how to eliminate the leakage of oil from under the valve cover.

What is the valve cover?

This element of the internal combustion engine is designed to protect the gas distribution mechanism from getting into it dirt, dust and moisture. In addition, the cover protects all the engine compartment from the oil, which is supplied under pressure for lubrication of the timing.

The first internal combustion engines did not have a valve cover, because of which the timing mechanism constantly had to be washed and cleaned. Over time, the timing was covered with stamped covers made of thin sheet steel. Today, this element is made of aluminum by casting. And this is not just a cover, but an entire structure, whose tasks include protection of the timing, participation in the crankcase ventilation process, and the collection of oil sprayed by the moving parts of the timing mechanism.

In order to ensure tightness, the valve cover is attached to the cylinder head through a rubber or silicone gasket. In some new cars, the gasket is not put at all: its role is performed by a layer of special sealant.

Possible leak locations

If you notice that the oil flows from under the valve cover, try to pinpoint the leakage location. Most often, the lubricant can flow out:

• In places of connection of a cover with a head of the block of cylinders owing to deterioration of a lining or superfluous pressure in system;
• In places of bolted connection of the cover to the cylinder head;
• From the oil filler neck.

In rare cases, oil leakage may occur on the lid body itself. This may be due to mechanical damage or factory rejection during casting.

Causes of oil leakage from under the valve cover

The leakage of oil from under the valve cover can be due to two factors:

• Loss of their sealing properties;
• Increase of oil pressure in the system.

In the first case, the gasket, due to the considerable operating time and the influence of high temperature, simply coarsens or breaks, which can not but affect the integrity of the system. This is not the worst case. It is enough to change the old gasket to a new one, and the tightness will be restored.

But if oil leakages from the valve cover are caused by increased pressure inside the system, further diagnostics will be required. And you need to start it by measuring the pressure.

How to measure the oil pressure

As already mentioned, the lubricant circulates through special channels inside the engine under the pressure created by the oil pump. Normal oil pressure for each engine is different, it all depends on its volume, the number of cylinders, valves, etc. In order not to guess, look in the manual of your car, everything is indicated there. So, if the pressure in the system decreases, its sensor will immediately signal to you about this lamp on the dashboard. If there is an increase, he will not react in any way. In other words, high pressure can only be determined by connecting a special liquid manometer to the engine instead of the sensor. Being guided by its indications, it can be concluded that the oil flows from under the valve cover due to the increase in pressure in the system, or the cause is still in the gasket (seals).

About what high oil pressure says

For a car, as for a person, "hypertension" does not bode well. In our case, it is evidence of a malfunction in the lubrication system. So, if in your car oil flows from under the valve cover, and you diagnosed increasing its pressure, the reason for this may be:

• Violation of normal crankcase ventilation due to clogging of the oil separator grids;
• Clogging of oil channels of a head of the block of cylinders;
• Clogged oil filter;
• Jamming of the pressure relief valve in the closed position.

Consider these reasons in more detail, and in the order in which it is better to carry out the diagnosis: from the simplest to the most complex.

Malfunction of normal crankcase ventilation

Let's start with the most common reason for increasing the pressure in the lubrication system found in domestic cars. Most often, the oil from under the valve cover of the VAZ starts to ooze due to a malfunction of the crankcase ventilation. Simply put, crankcase gases, which are free to leave the engine, encounter obstructions in their path, and begin to accumulate inside, creating excessive pressure. In this case, it not only presses oil from under the valve cover, but can also be thrown out through the breather into the air filter housing.

What kind of obstacles can this be? First, the oil separator grid, if it is clogged with combustion products. And secondly, the usual deposits and dirt on the inner walls of the fittings, to which the ventilation hoses are attached. So, if driving oil from under the valve cover in our car, do not be lazy to remove the valve cover and rinse the oil separator net, and at the same time clean the fittings.

Clogging of oil channels and filter

The head of the block of cylinders has a whole network of special channels, through which the oil moves. The use of low-quality lubricant, getting into the mud system, overheating of the engine are the main reasons why these channels can become clogged. When this happens, the oil pressure naturally increases, because the oil pump continues to work.

The same happens when the filter clogs. It loses its throughput, creating an increased pressure in the system. And there is nothing surprising in that the oil flows from under the valve cover, if you changed the filter several years ago.

This problem is eliminated by replacing the filter element and flushing the system using special fluids.

Malfunction of the pressure relief valve

Often increasing the oil pressure is a consequence of the malfunction of the oil pump pressure regulator, because it regulates it. The most common cause of the malfunction is jamming in the closed position caused by the ingress of friction products (small shavings) or dirt into its mechanism. It is not difficult to get rid of this problem. The valve is easily disassembled and cleaned, however for this purpose it will be necessary to dismantle the oil pump.

Select the valve cover gasket

Pay enough attention to the selection of the gasket, since you will not be able to eliminate the leakage of oil from under the valve cover using a defective product. Preference here is better to give the original spare parts, after learning its factory catalog number. If the design provides a rubber gasket, make sure that the rubber was soft and had no cracks or tensions. All these defects will necessarily affect the tightness.

Do I need to lubricate the rubber seal with sealant?

As for the use of sealant, the opinions of the mechanics differ. Some consider its use unacceptable, while others, on the contrary, argue that only with it you can achieve full tightness. Let's just say, if the surfaces of the cover and the cylinder block have roughness, the use of a sealant is desirable, but only if it is applied with a neat thin layer. If the surfaces are perfectly flat, you can do without it, because a few years ago, no one used such a sealant. Well and for cars where the lining is not provided by a design, without hermetic not to manage.

If the oil flows from the neck or in places of bolted connections

It happens that the oil does not flow from the place where the cylinder head and valve cover surfaces are connected, but, for example, from the oil filler neck or where there is a bolted connection. The reason for these leaks is all the same excess pressure. Having eliminated the reasons of the raised pressure, it is recommended to replace rubber sealants of bolts (if they are provided by a design), and also to check up tightness of a cover маслозаливной a mouth.

Helpful Tips

Finally, here are some useful tips that will help you avoid problems with oil leakage or to deal with them faster.

1. Timely replace the oil in the engine, as well as the oil filter.
2. Use only high-quality grease.
3. Do not allow grease, water, other process fluids to enter the system.
4. When passing the maintenance, do not forget to check the oil pressure in the lubrication system. If it is found, immediately repair the car.
5. Do not allow the engine to overheat.
6. Check the operation of the units responsible for the ventilation of the crankcase.
7. When choosing a gasket for the valve cover, give preference to the original product.
8. Apply sealant to the gasket with a thin continuous layer. Do not allow it to hit the gas distributor.
9. While tightening the valve cover, do not over tighten the bolts.
10. After detecting leakage of oil from under the valve cover, do not tighten with diagnostics and repair.