The causes of knocking in the engine may be other malfunctions, which are described below.
Valve noise when starting the engine
When starting the engine, the hydraulic pushers immediately come into operation; for this, special check valves are used. They are designed to fill the lubrication system and the oil channel of hydraulic pushers and camshaft bearings with oil.
If the engine has not been running for a long time, valve knocking is not the cause of the breakdown. The fact is that when the engine has not been running for a long time, oil drains from the hydraulic pushers. When the engine is started, the hydraulic pushers fill with oil, and the knock disappears.
If the knock of valves in the area of the cylinder head continues on a warm engine, this indicates defects in one or more hydraulic pushers. They are beyond repair and should be replaced.
The cause of valve knocking, lasting from a few seconds to 10 minutes, may be the following:
- before starting the engine, the oil was changed in it;
- the engine has not been running for more than a day;
- engine starts after repair (pusher replacements).
Checking hydraulic pushers
1. Warm up the engine to operating temperature and let it idle until the fan turns on.
2. Run the engine at high speed for 2 minutes (2500 min-1).
3. If valve knocking continues, stop the engine.
4. Remove the cylinder head cover.
5. Turn the engine crankshaft so that the camshaft cams of the cylinder being checked are directed upwards.
Pic. 5.2. Checking hydraulic pushers: 1 - pin; 2 - pusher
6. Wooden or plastic pin 1 (pic. 5.2) press the pusher 2.
Attention! Do not use a metal tool, as this leads to scratches.
If you feel «air» until the valve opens, or the pusher drops quickly and without resistance, which means that the pusher needs to be replaced. This work should be done by specialists in a car repair shop.
Overspeed and engine life
High RPM reduces the life of the engine. If the engine is running at high speeds and atypical knocks or noises are heard, this indicates wear on the crankshaft or valve train. If the wear is strong, then the pusher may break, the valve and cylinder will not work. You will feel it by the reduction in engine power. The worst option is the destruction of the valve springs and the ingress of debris on the moving piston. As a rule, this leads to serious engine damage.