What are the symptoms of small valve clearance?
2 Answers
The symptoms of excessively small valve clearance are valve leakage and erosion of the valve seat. Below is relevant information about valves: 1. Function of valves: Valves are specifically responsible for introducing air into the engine and expelling exhaust gases after combustion. Structurally, they are divided into intake valves and exhaust valves. The intake valve's role is to draw air into the engine to mix with fuel for combustion; the exhaust valve's role is to expel the combustion exhaust gases and dissipate heat. 2. Composition of valves: Valves consist of a valve head and stem. The head operates at high temperatures and withstands gas pressure, valve spring forces, and the inertia of transmission components, with poor lubrication and cooling conditions. Therefore, valves must possess certain strength, stiffness, heat resistance, and wear resistance.
Back when I drove my old car, I encountered the issue of valve clearance being adjusted too small. The idle speed was always unstable, with RPMs fluctuating up and down, and the steering wheel shaking like it was dancing disco. Acceleration was sluggish too—stepping on the gas pedal took forever to get any response, and climbing hills felt especially strenuous, as if the engine was slacking off. After cold starts, there was a regular clicking sound from under the hood, annoying enough to keep me awake. Fuel consumption soared, jumping from 7 liters to over 9 liters, costing me hundreds more in gas money. Once on a long highway trip, some white smoke appeared, scaring me into pulling over immediately. During the repair check, I learned that the tight clearance caused the valves not to seal properly, leaking power and wasting fuel, while thermal expansion made the valves stick, creating noise and overheating. Not fixing it in time could have burned out the valves, with repairs costing several thousand. Now, during every maintenance session, I remind the mechanic to check the clearance, and the problem hasn’t recurred since.
