Signs of a punched cylinder head gasket
Content
The cylinder head (cylinder head) is one of the main components in an internal combustion engine. This assembly can be conditionally called a cover that covers the cylinder block from above.
However, in most modern power units, the functional purpose of the cylinder head is much wider and is not limited to simple protection. As a rule, candles, nozzles, valves, camshaft and other parts are placed in it.
Also in the cylinder head are channels for the circulation of lubricant and coolant. The head is screwed to the cylinder block, and a sealing gasket is placed between them, the main purpose of which is to reliably isolate the cylinders from the external environment and from each other in order to prevent gas leakage from the combustion chambers.
The cylinder head gasket also prevents leakage of engine oil and antifreeze and prevents fluids from mixing with each other. The gasket can be solid copper or made of several layers of steel, between which there are layers of highly elastic polymer (elastomer).
You can find elastomeric gaskets on a steel frame. A composite material based on asbestos and rubber (paronite) is also often used, but this technology is already considered obsolete. Under certain conditions, this part may be damaged.
A blown head gasket looks something like this
Breakdown does not happen so rarely and threatens with very unpleasant consequences. Therefore, it will not be superfluous to know what leads to this and how to act in such a situation.
Why breakdown occurs
Often, a breakdown is the result of improper installation of the head or gasket. Installation and fixing of the cylinder head must be carried out according to a strict scheme in accordance with the manufacturer's instructions.
When tightening bolts, a certain sequence must be followed, and tightening must be done with a precisely specified torque. In many cases, the bolts themselves are not suitable for reuse; they must be replaced with new ones when replacing the gasket and do not forget to lubricate the threads.
Violation of these rules leads to an uneven fit of the surfaces to be joined and leakage. Sometimes the manufacturer recommends re-tightening the bolts some time after assembly to compensate for the effects of heat and vibration. Do not neglect this recommendation.
The fit may also be uneven if the mating surfaces are curved, dirty or have defects - bulges, gouges, scratches. Therefore, before assembling, carefully inspect the mating surfaces of the cylinder block, head and gasket to make sure that they are free of dirt and damage.
One of the main reasons leading to the breakdown of the cylinder head gasket is overheating of the motor. Overheating the engine can lead to many negative consequences, including deformation of the gasket and the surfaces adjacent to it.
And the unit overheats in most cases due to problems in the cooling system - a faulty thermostat, an idle pump, insufficient coolant level (coolant). Finally, the poor quality of the gasket itself can result in its breakdown some time after installation. With this, everything is clear - it is better to avoid saving on critical things.
Breakdown signs
Some symptoms clearly point to cylinder head gasket damage, others are not so obvious. Although the motor may continue to run steadily for some time, it is important not to miss the moment and not bring the situation to a critical point.
- Obvious signs include the exit of exhaust gases to the outside of the engine. It is noticeable visually and is usually accompanied by loud pops from under the hood.
- If the damage has affected the passage of the channel of the cooling system, gases can enter the coolant. Seething or foam is usually clearly visible when the cap of the expansion tank or radiator is removed (be careful, the system is under pressure!). Due to the presence of gas in the liquid, the cooling system hoses can swell and become hard.
- The reverse process is also possible, when antifreeze flows into the combustion chamber through damage to the gasket. This is usually indicated by white smoke from the muffler, which appears not only during the engine warm-up or high humidity. After a while, a drop in the coolant level becomes noticeable. The penetration of antifreeze into the cylinders is also indicated by wet candles or heavy soot on them.
- If oily spots are visible in the expansion tank of the cooling system, and there is a coating on the inside of the oil filler cap that resembles yellowish sour cream, then the coolant and engine oil have mixed. This emulsion can also be found on the dipstick. And most likely the reason for this is damage to the cylinder head gasket.
- When mixing liquids, such a seemingly paradoxical phenomenon as an increase in the oil level can sometimes be observed. But there is nothing strange about this, because when antifreeze enters the lubrication system, it dilutes the oil, increasing its amount. Of course, the quality of the motor lubrication deteriorates sharply, and the wear of parts increases.
- Since the cooling system is often affected during the breakdown of the gasket, this negatively affects the removal of heat from the motor and its temperature rises noticeably.
- Unstable operation of the engine, tripping, power drop, increase in fuel consumption can be observed if the partition between the cylinders is destroyed at the gasket.
- If the cylinder head is installed incorrectly or the gasket is punctured on its outer side, leaks or leaks may appear on the engine.
How to check the cylinder block gasket
There are not always obvious signs of gasket breakdown. In some cases, additional checks are needed. For example, unstable operation and increased gluttony of the engine may have different origins.
Clarity in this situation will make a compression test. If it is close in value in neighboring cylinders, but differs markedly from others, then most likely the wall of the gasket between the cylinders is damaged.
When gases enter the cooling system in small quantities, the bubbles in the expansion tank will be invisible. If you put a sealed plastic or rubber bag on the neck (here the condom, finally, came in handy!) And start the engine, then if there are gases in the antifreeze, it will gradually inflate.
What to do when the cylinder head gasket is damaged
If it turns out that the gasket is punctured, it must be urgently replaced. There are no options here. It is not too expensive, although much more will have to be paid for the work of replacing it, given that this process is quite complicated and time-consuming. It is highly undesirable to continue driving a car with a punctured cylinder head gasket, since one problem will soon necessarily pull others along with it.
Head deformation due to overheating, rupture of cooling system hoses, engine jamming - this is not a complete list. Accordingly, the cost of repairs will increase. When buying, do not bother too much with the gasket material; it has little effect on the durability of the part. Much more important is the quality of its manufacture, because you, of course, do not want to face the same problem again after some time.
Therefore, it is better to buy a branded gasket or an analogue of a reliable manufacturer. And don't forget to get new bolts. An old gasket should not be installed, even if it is not damaged, since re-crimping does not guarantee a reliable and tight seal.
If there are defects on the mating planes of the cylinder block and head, they will need to be ground. It is better to use a special precision machine, although with experience and patience it is possible to grind with a grinding wheel and even sandpaper.
The layer removed as a result of grinding must be compensated for by an increased thickness of the gasket. This must be taken into account when buying.
If, as a result of a breakdown, antifreeze and engine oil are mixed, you will have to flush the lubrication system and cooling system and replace both workers. liquids.
