How to Adjust Car Valves?
3 Answers
Adjusting car valves involves the following steps: 1. Rotate the engine crankshaft to position a cylinder at the top dead center of the compression stroke; 2. Loosen the valve adjustment screw on the rocker arm and tighten the nut, then insert a tool between the valve stem and the rocker arm; 3. Turn the adjustment screw and remove the tool; 4. Rotate the crankshaft and adjust the valve clearance for the remaining cylinders using the same method. The function of valves is to: intake air into the engine and expel exhaust gases after combustion. Engine structure can be divided into: 1. Intake valves, which draw air into the engine to mix with fuel for combustion; 2. Exhaust valves, which expel combustion gases and dissipate heat.
Last time I adjusted the valve clearance on my old car's engine, here's how I did it: First, remember to remove all the spark plugs to make turning the crankshaft easier. Locate the top dead center position of the cylinder, then slowly rotate the crankshaft pulley until the valve reaches its highest point. Use a feeler gauge to measure the clearance - the 0.2mm blade should slide in with slight resistance for proper adjustment. You'll need two wrenches to adjust the screw, and be extra careful not to lose the clearance when tightening the lock nut. After adjusting all four cylinders, double-check the settings, otherwise the engine will develop a 'ticking' sound. It's best to perform the entire process on a cold engine, and be careful not to drop tools into the engine bay. Lay down a cloth if there's too much oil residue to work on.
Most new cars nowadays use hydraulic lifters that don't require adjusting clearance, but older mechanical tappet engines need manual adjustment. Be gentle when removing the valve cover - those rubber gaskets tend to age and crack. After adjustment, remember to clean off any residual oil traces from the sealing strip before reassembly, otherwise it will definitely leak oil within six months. When turning the crankshaft, don't force it with a wrench; use a 19mm socket for gentle rotation to avoid damaging the pulley. Experience tells me valve adjustment is most accurate at room temperatures between 10-20°C - adjustments made in extreme cold will cause noise when summer comes.
