Under normal conditions, amount of gas flowing out of high-speed gasoline engine piston and piston ring assembly should be less than 1% of intake air volume. increased power loss, increased fuel consumption and deterioration of lubricating oil quality.
Due to high temperature of crankcase gases, as well as dust and alumina mixed with intake air, this not only accelerates wear of parts, but also increases viscosity of engine oil and turns oil black. ; in addition, when blow-by gases increase, it is difficult to cool due to gas, and oil often evaporates into white smoke and is thrown out of oil pan, causing machine parts to overheat.
Due to formation of blow-by gases, temperature of piston and piston ring rises, causing lubricating oil in annular groove and ring to ablate and stick together. The piston ring loses elasticity, gets stuck or breaks, which increases number of malfunctions and exacerbates wear of parts.
Degraded lubricating oil and ring sticking increase cylinder, piston and ring wear and exacerbate early wear and corrosion of other related parts. In addition, due to increased pressure in crankcase, oil losses increase, increasing oil consumption. It can be seen that blowing engine is very harmful.
[Reason for engine failure]
The piston ring does not fit, breaks and wears out, resulting in poor cylinder sealing and gas purge;
The opening gap of piston ring, as well as side and back gaps, are too large for formation of blow-by gases;
The air filter is installed incorrectly or filter element is damaged, and a large amount of dust and impurities are sucked into cylinder, causing wear, resulting in poor sealing of cylinder and blowing out gas;
Cylinder head bolts not tightened to normal torque, cylinder gasket loose, gas escaping machine;
Valve and valve seat not sealed;
The cooling system is seriously lacking water and temperature rises sharply;
The piston is partially stuck to piston ring and cylinder liner, and piston has a large deformation area. Causes an engine breakdown.
[Diagnosis and troubleshooting of gas blow-by problems]
Crankcase blow-by in an engine is a relatively complex malfunction. Gas breakthrough is one of most common engine malfunctions. Gas breakthrough is part of expansion gases formed at high temperature and high pressure. in cylinder during operation, which is removed from body through anomalous channels - an external phenomenon.
Its appearance and development seriously threatens normal operation of engine. If it is light, it will reduce power output, waste energy, and if severe, it will damage machine parts and cause an accident.
When engine is scavenged, pressure and temperature at end of engine compression and combustion pressure will decrease, resulting in difficult starting, insufficient power, and increased fuel consumption.
In event of a strong blow-by, engine cannot be started.
The strong sound of crankcase gases is similar to a knock in a cylinder. When oil filler cap is opened, a large amount of gas escapes.
Common engine parts that emit gases include valve cover gas leakage, oil filler gas leakage, and white smoke.
For engines with blow-by problems, first check filtering effect of air filter (for example, presence of dust on inner wall of intake manifold of a diesel engine);
Check whether filter element is damaged. If filter does not work and dust and impurities enter cylinder, this will inevitably cause severe wear and even scuffing of cylinder and breakage of ring, which will inevitably lead to blow-by gases. .
In addition, if valve and guide tube are worn and loose and seat clearance exceeds allowable gap, some gas will escape from valve chamber cover through gap.
In case of gas breakthrough in cylinders, first check pressure in cylinders one by one using pressure gauge. The pressure difference in each cylinder should not exceed 10% of its average value.
Engine gas breakthrough and poor sealing lead to abnormal cylinder and piston (ring) wear, excessive engine oil consumption and oxidative wear, engine overheating, piston (ring) sticking to cylinders, melt wear and piston ring breakage, and other accidents main factor.
When pressure in cylinder drops, to find out cause of decrease, you can inject a small amount of fresh engine oil into cylinder from spark plug hole, and then measure pressure again; intake manifold vacuum degree can also be checked to judge engine leakage.
On this basis, analyze cause, then prescribe right remedy to eliminate it, and take effective measures to prevent it in order to prevent such failures from occurring.