Valve noise when starting the engine
When the engine has not been running for a long time, valve knocking is not the cause of the breakdown. When the engine is not running for a long time, the oil from the hydraulic tappets drains. When the engine is started, the hydraulic pushers immediately 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 causes of valve knocking can be the following:
- 1. Before starting the engine, the oil was changed in it.
- 2. The engine did not work for more than a day.
- 3. The engine starts after replacing the pushers.
The principle of hydraulic adjustment of thermal valve clearances
Pic. 4.18. Hydraulic pusher in the context: 1 - camshaft; 2 - oil reservoir in the body; 3 - check valve; 4 – oil supply channel; 5 – high pressure zone; 6 - valve stem; 7 - spring; 8 - cylinder; 9 - piston; 10 - hydraulic pusher body
Hydraulic pushers consist of two main parts - a piston and a cylinder (pic. 4.18). The spring presses the piston against the surface of the pusher. When the valve is closed, oil flows from the engine lubrication system through the oil gallery in the block head through the overflow hole in the pusher housing into the pusher cylinder. The pusher check valve is open and oil fills the piston grooves. When the camshaft cam is pressed on the pusher, its body presses on the piston, under the influence of which the valve closes and stops the oil bypass. Since the liquid is not compressible, the oil in this case serves as a rigid connection between the camshaft cam and the valve stem, so there is no gap when the valve is pressed. In this case, the pressure difference is compensated by bypassing oil from the pusher cylinder into its housing, providing additional lubrication of the working parts of the camshaft cams. After closing the valve, the pressure in the pusher body drops, the check valve opens, and the cylinder is again filled with oil.
During long-term operation of the engine, parts of the valve mechanism wear out, however, due to the principle of operation of hydraulic pushers, valve clearances can be checked after a relatively long period of time.
Checking hydraulic pushers
1. Warm up the engine.
2. Let the engine idle until the fan turns on for the first time.
3. Let the engine run for 2 minutes at high speed (2500 min-1).
4. Turn off the engine.
5. Remove the cylinder head cover.
6. Turn the engine until the camshaft cams of the cylinder being checked are pointing upwards.
Pic. 4.19. Checking the hydraulic pusher: 1 - pusher; 2 - wedge
7. Use a wooden or plastic pin to press the pusher (pic. 4.19).
8. If at the same time the pusher drops quickly and without resistance, it should be replaced. This work should be done by specialists in a car repair shop.
Work at high speeds
High speed operation reduces the life of the engine. If the engine is running at high speeds and knocks or noises are heard, this indicates wear on the crankshaft or valve mechanism. If the wear is strong, then the pusher may break. As a rule, this leads to serious engine damage.
Some malfunctions of hydraulic pushers, their causes and remedies are given in table.