How to find if you have a bad gasket?

A cylinder gasket is installed between the cylinder head and the cylinder block. The cylinder head bolts are used to ensure the sealing of the cylinder and prevent leakage of gas, cooling water and lubricating oil. The high-temperature and high-pressure gas generated in the cylinder and the cooling water and oil with a certain pressure and flow through the cylinder liner must be tightly sealed, and can withstand the corrosion of water, gas and oil. 

The ablation of ordinary gaskets is due to the impact of high-temperature and high-pressure gas on gaskets, bag mouth, rings and asbestos plates, resulting in leakage of steel cylinders, oil and cooling water. In case of failure, the engine power decreases, the cylinder pressure is insufficient, and the exhaust pipe breaks, the cylinder gasket shall be replaced immediately.

1. Cylinder gasket ablation fault phenomenon

（1）Burn loss between two cylinder edges of the cylinder gasket: the power of the starting strategic engine is obviously insufficient, the car is unable to drive safely, and the acceleration is poor. Take down the air filter. When the engine is idling, the air inlet pipe mouth can hear a "snapping" sound.

（2）The burned part of the cylinder gasket is connected with the water jacket hole: the water tank starts to bubble, open the boiler, and exhaust white smoke.

（3）The combustion part of the air cushion is connected with the oil circuit: part of the oil flows into the cylinder and is ablated, and the exhaust gas emits blue smoke.

（4） The burned part of the cylinder gasket is related to the external atmospheric environment: the engine lacks power, the economy deteriorates, and the damaged part has strong cracks.

2. Causes of cylinder gasket ablation

（1）When the engine works under heavy load for a long time, knock combustion often occurs, which causes local high-temperature and high-pressure ablation of the cylinder gasket in the cylinder.

（2） When bolts are used to fasten the cylinder head, students are not required to manage and operate according to the regulations, and the uneven torque problem causes the cylinder gasket not to stick smoothly on the joint surface between the cylinder block and the cylinder head, which directly leads to gas channeling.

（3） If the ignition advance angle or injection advance angle is too large, the maximum pressure and temperature of the cycle will be too high.

（4）The quality of the cylinder gasket is poor, the thickness is uneven, there are bubbles at the mouth of the bag, the asbestos is unevenly laid or the wrapping is not tight.

（5） The cylinder head is warped and deformed, the flatness of the cylinder block is out of tolerance, some cylinder head bolts are loose, and the sealing is not tight.

（6）The driving technology operation and management method is improper, and the driver is used to accelerating and running at a high speed. Excessive pressure aggravates the erosion of the cylinder gasket.

3. Cylinder gasket ablation diagnosis

Check the compression pressure of two adjacent cylinders of the engine with a cylinder pressure gauge. If the compression pressure of both cylinders is very low, it is usually due to poor sealing of the cylinder gasket. Then carry out the following specific tests:

(1) Check the sealing condition of cylinder gasket with rubber hose

Start the engine, and place one end of the rubber hose close to the ear, and the other end along the joint between the cylinder head and the cylinder block that may be poorly sealed. If the sealing of the cylinder gasket is poor, you can clearly hear the bleeding sound at the air leakage place.

⑵ Check the tightness of the working cylinder gasket by looking at the radiator spray

Open the radiator cap, keep the engine idling, observe the radiator coolant filler, and quickly step down the accelerator pedal to the bottom. If the coolant continuously sprays bubbles when accelerating suddenly, it indicates that the cylinder gasket is not well sealed. The more bubbles, the more serious the leakage. Under severe idling conditions, the radiator port will turn over.

(3) Test the sealing performance of cylinder gasket with exhaust gas analyzer

Some engine radiator coolant filler holes are under the iron plate, and no bubbles can be seen. Open the radiator cap, place the probe of the exhaust gas analyzer on the open radiator cap, and do not touch the coolant. If HC can be detected during rapid acceleration, the cylinder gasket seal is poor.

(4) Air leakage of the cylinder gasket will affect the engine working temperature too high

If the power is reduced, the cylinder head shall be replaced in time, otherwise the cylinder head may be damaged, the cylinder head shall be scrapped, and the coolant may enter the combustion chamber.

(5) When the engine is working, if you feel the air impacting your hands, move your hands around the cylinder gasket. When the gasket is seriously damaged, the gasket seal is invalid because bubbles emerge from the joint between the cylinder head and the cylinder block.

(6)During use, it is found that when the water level in the water tank drops rapidly, pull out the dipstick to check that there is water in the oil (the oil color turns yellow or even white), which causes air leakage of the cylinder gasket; In addition, the temperature of the cooling water in the water tank rises too fast, the boiler often boils down, and the water inlet splashes. However, the water inlet pipe has no depression, and the cooling water has no obvious consumption, leading to the leakage of the cylinder liner gasket. If the above phenomenon occurs, replace the cylinder gasket with a new one.

4. Use and maintenance of cylinder gasket

In use, the cylinder gasket shall have sufficient strength under the protection of high-temperature and high-pressure environmental gas, and be not easy to be damaged. It shall also develop the characteristics of heat-resistant and corrosion-resistant materials; It has a certain time elasticity, can compensate a flatness of the joint surface, and has its own good sealing property; The cylinder is easy to disassemble, non stick and has a long service life. At present, asbestos cylinder gasket is widely studied and used in our country. Its structure is asbestos with metal wire sandwiched between it, copper sheet is used to edge around the water hole, and copper sheet is used to inlay the combustion chamber hole to prevent high-temperature ablation. Attention shall be paid to the following problems during installation and maintenance:

(1) Dismantle the cylinder head bolts and replace the cylinder gasket after the engine is completely cooled to avoid deflection and deformation of the cylinder head.

(2) Check whether the surface of the cylinder gasket is concave, protruding or damaged; Check whether the flatness of the cylinder head and cylinder block meets the requirements, then clean the cylinder gasket, cylinder head and cylinder block, and dry them with high-pressure air to prevent dirt from affecting the sealing.

(3) The selected cylinder gasket must be an original accessory with reliable quality and meet the requirements (specification and model). During installation, pay attention to the upper and lower orientation marks to prevent reverse installation and human failure.

(4) Tighten the cylinder head bolts according to the technical management specifications. Due to the cross problem of symmetrical expansion of business from the central government to both ends, tighten them to the specified torque in 2~4 times; It is safer and more reliable to fasten once again in the hot car state.

(5) Do not remove the rusted cylinder head bolts. Do not use iron to harden the bolts to avoid damaging the cylinder head. Inject kerosene into the screw hole of the cylinder head to soak it for a while, and then remove it smoothly.

(6) Improper storage, disassembly and assembly of cylinder head, damage and deformation of cylinder gasket, improper cleaning during installation will lead to poor operation quality, poor sealing, artificial failure and other problems, which must be paid attention to.