Malfunctions of the exhaust valve
- wedge of the valve stem;
- clogging and contamination of the valve;
- deposits on the valve stem;
- insufficient sleeve clearance;
- deformation of the valve;
- valve burnout;
- damage to the valve mounting;
- damage or distortion of the spring;
- metal corrosion.
Symptoms of the exhaust valve faults
- high pressure of the exhaust gases;
- engine detonation;
- increased fuel consumption;
- “Check Engine” indicator reading on the instrument panel;
- fast engine overload;
- excessive condensation on the engine;
- smell of exhaust fumes inside the vehicle.
Causes of of the exhaust valve faults
- use of fuels with lower octane or impurities comprising heavy metals;
- excessive engine overheating;
- long engine run at idle speed;
- use of low-quality motor oil;
- oil burning and chemical decay;
- use of low-quality valves;
- overheating and subsequent deformation of the stem;
- failure of the fuel mixture system.
Diagnostics
Start the diagnosis with an inspection. First assess the state of the valve in the system. You also need to check its location and contact tightness. The optimum value of the contact surface width is 1,15-1,5 mm.
Further, check the gap between the valve and the piston. The piston must be turned by hand to its maximum extension. The standard value clearance is 2.5 mm. If it is less, there is a danger of the valve striking the piston, followed by an immediate destruction of the first.
You should also check the contamination level of the valve. In case of severe fouling or sticking of the combustion and the oil decay products it is required to clean the valve. For cleaning use alcohol-based solutions.
Repair and replacement of the exhaust valve
A damaged valve cannot be restored. Despite the fact that it is molded from high-strength metal alloy, at melting or deforming it only requires replacement.
To replace the valve, it is neccessary to remove the crankcase, so this kind of work, is recommended to carry out only at service stations. After installing the new part you need to grind in the valve to the cylinder seat with special grinding compound.
When disassembling the engine it is highly recommended to sign the components with a marker to avoid incorrect connection and further discrepancy of componennts. After installation of the engine a test drive is carried out at medium engine speeds.
Engine exhaust valve finder for