What is the reason for the valves being quiet when cold but noisy when hot?

[LaLayla]

The reason for the valves being quiet when cold but noisy when hot is: If the valves are noisy when the engine is hot, this indicates that there is clearance in the valves. It is necessary to check whether the engine oil is insufficient. If the engine oil level is normal, then the valves need to be replaced. During cold starts, due to the high viscosity and poor fluidity of the engine oil, there may be operational noise in the short term, and slight sounds may occur when the moving parts come into contact. This situation is normal and there is no need to worry. A cold start refers to starting the engine when the car has been parked for a long time and the car's temperature is the same as the ambient temperature. Many car owners hear a clicking abnormal noise from the engine compartment during cold starts. This noise sounds very abnormal, unlike the performance of a car running normally.

[Zane]

This is a common issue I encounter, especially when driving older cars. When starting a cold engine, the parts contract tightly, with minimal valve clearance or just enough oil lubrication, so it runs quietly without noise. But once it heats up, the expansion increases, components like hydraulic lifters or valve springs stretch out, and the friction sounds between metal parts become noticeable, particularly during uphill acceleration. Sometimes it's due to poor oil quality that thins out when hot, failing to provide adequate lubrication. It's best to check the valve clearance settings and oil viscosity; switching to a thicker summer-grade oil might help. If not repaired promptly, the noise could worsen and potentially damage the engine, so it's advisable to visit a professional shop for adjustment as soon as the issue is noticed.

[SimonLee]

I've been driving for over a decade and know how annoying this kind of noise can be. When the engine is cold, it doesn't make noise because the thick oil provides good protection and the valve components remain stable. After the engine warms up and the temperature rises, parts expand causing increased clearances, the oil film thins leaving small gaps, and the whooshing sound emerges. This is especially common in older models or those with worn hydraulic lifters, as thermal expansion makes components more prone to looseness and noise. I recommend checking your engine's oil pressure and trying fresh oil. Don't neglect routine maintenance - regularly inspect the valve system to prevent minor issues from becoming major problems.

[EmilianoDella]

I've encountered a similar situation before, where the car made creaking noises when it got hot. It's mainly due to thermal expansion effects: when the engine is cold, everything is tight and silent, but as it heats up, metal parts expand, gaps loosen, and noises occur. It could also be that the engine oil is too thin, providing insufficient lubrication. Don't worry, a simple solution is to switch to high-quality oil and check the valve clearance – tighten it if necessary.