What are the symptoms of poor engine valve sealing?
3 Answers
Symptoms of poor engine valve sealing include: 1. Vehicle shaking and failure to start; 2. Decreased cylinder pressure, incomplete combustion, leading to carbon buildup; 3. Accelerated wear of pistons and cylinder liners. Causes of poor engine valve sealing are: 1. Insufficient valve clearance; 2. Excessive carbon deposits on the contact surface; 3. Deformation of the valve seat, valve tip, or rocker arm; 4. Spring failure. The function of the valve is to specifically input air into the engine and expel exhaust gases after combustion. Based on engine structure, valves are categorized into: 1. Intake valve: Draws air into the engine to mix with fuel for combustion; 2. Exhaust valve: Expels combustion exhaust gases and dissipates heat.
I've experienced the issue of engine valve leakage before. The most obvious symptom is difficulty during cold starts – it takes three or four cranks to get the engine going in the morning. At idle, the steering wheel shakes like a massage chair, and the RPM needle dances up and down. When driving on the highway, acceleration feels sluggish; even flooring the gas pedal doesn't provide much power, especially noticeable when going uphill. The sudden spike in fuel consumption is the most frustrating part – the same route now burns one-third more fuel. The exhaust pipe may backfire with popping sounds or emit black smoke, and if you listen carefully, you can hear a hissing air leakage sound from the engine. When these symptoms appear, there's an 80% chance it's a valve sealing problem that needs immediate repair, otherwise, the piston rings will suffer collateral damage.
A poorly sealing valve is no small matter—it can significantly reduce cylinder pressure. I once worked on a car where the owner complained about sluggish acceleration. After testing, we found the cylinder pressure was 20% below the standard value. This air leakage caused incomplete combustion of the air-fuel mixture, resulting in strong gasoline fumes from the exhaust and heavy carbon buildup on the inner walls of the tailpipe. Difficult cold starts occur due to insufficient cylinder pressure from the leakage, which improves slightly when the engine warms up but still leads to rough idling. The biggest headache is the chain reaction of issues it can trigger, such as burning oil (blue smoke) as engine oil seeps into the combustion chamber through the valve stem gaps. If you hear a ticking noise, pay extra attention—it could indicate increased valve clearance or worn lifters.
