There are two types of valves: the exhaust valve and the intake valve. A cylinder has at least one of each, but your engine configuration may include:
- 3 per cylinder (2 intake, 1 exhaust)
- 4 per cylinder (2 admissions, 2 exhaust)
- 5 per cylinder (3 admissions, 2 exhaust)
In the 4-stroke engine, the purpose of the intake valves is to open and close at a precise moment to introduce fresh gases into the combustion chamber; for the exhaust valves, they open and close at a precise moment for the evacuation of the burnt gases in the exhaust manifold.
The valves are formed of a tulip, which closes the intake or exhaust duct, extended by a cylindrical tail passing through a guide, and opening in the vicinity of the camshaft, which actuate them periodically in translation: the sealing between the cylinder head on the oil side and the combustion chamber on the engine side is ensured by the valve stem seal.
The valve stem seal is from the family of lip seals, or SPI seals. Its largest diameter is fitted on the valve guide and the smallest, consisting of a cylindrical lip circled by a circular spring, seals on the valve stem, which performs its translation.
The valve stem seals the valve, preventing oil stored in the cylinder head from entering the cylinder.
Replacement of the valve stem seal is required after the following symptoms are apparent:
- Abnormal oil consumption
- Characteristic blue fumes in deceleration: the engine draws oil through the valve shanks, the pressure in the cylinders being low due to the absence of engine combustion.
In the case of diesel engines, if the valves are in the longitudinal axis of the piston previously positioned at the TDC, they are unhooked from their return spring and placed on the piston head; the valve stem seals are then accessible and can be replaced. If the engine turns accidentally at that moment, the piston goes down and the valve falls in the cylinder: the dismounting of the cylinder head is thus obligatory!
In a petrol engine, if the valve shaft forms an angle with the piston, a valve lock tool is introduced through the spark plug hole.
In some cases, removal of the cylinder head is mandatory, resulting in higher costs.
If you suspect that there may be an issue with your exhaust valve or a warning light has illuminated on your dashboard, contact our team at MCC Manchester Road. Our experts will perform your valve change Bradford.
Visit us at MCC Manchester Road Ltd, 662 Manchester Road, Bradford, West Yorkshire, BD5 7NL
Telephone: 01274 731322