Why Your Engine Knocks When Cold: Causes, Fixes & What to Watch For

An engine knocking noise doesn’t always signal a costly repair. It could stem from cold temperatures slowing down mechanical components or a misaligned piston in the cylinder. Additionally, the engine might need time to adjust to new motor oil, or the air-fuel mixture in the combustion chamber may not be properly balanced.

Why engines knock in cold weather

Several factors can cause an engine to produce a knocking noise. One primary reason for these sudden sounds is the cold weather experienced during winter months.

These problems might exist in warmer months, but cold winter temperatures can exacerbate them. This is particularly noticeable in older vehicles.

Knocking noises from an engine don’t point to a single issue. They are indicators of various underlying problems.

Below are some common reasons your engine might be making a knocking noise.

• Cold temperatures are slowing down certain engine components.
• The vehicle has over 200,000 miles, causing the piston to misalign in the cylinder.
• The engine has switched from light to heavier motor oil.
• The knocking sound isn’t from the engine but from worn parts needing repair or replacement.
• The air and fuel mixture in the combustion chamber is not at optimal levels.
• The motor oil hasn’t been changed recently.
• Sticky valve lifters are causing the noise.

These are the most frequent causes of engine knocking during cold weather.

Addressing engine knocking noises

Solving the knocking noise depends on its cause. Visit a mechanic to use diagnostic tools to pinpoint issues within your vehicle’s engine system.

Piston slap issues

If piston slap is causing the knocking, simply wait for the engine to warm up fully. No mechanic is needed, as this is often a sign of an aging vehicle.

However, if blue smoke accompanies the piston slap, it could indicate a serious problem, potentially leading to engine failure. What does blue smoke signify here?

Blue smoke suggests oil is leaking from the piston rings into the cylinder. If you notice blue smoke from the exhaust, replace the piston and its rings immediately.

Failing to act quickly may cause damage to spread to other engine components, leading to expensive repairs.

Aging engine issues

To reduce knocking in an older engine, let the vehicle warm up completely before driving. As vehicles age, their components become less efficient, which is a natural process.

Little can be done to eliminate knocking in an old engine. Regular checkups and cleaning out dirty motor oil when it accumulates are essential.

Sticky valve lifters

Valve lifters are critical to the engine’s combustion process. When they become sticky, it’s often due to infrequent vehicle use or overdue oil changes. Special cleaning products can address sticky valve lifters.

Using heavier motor oil

An engine needs time to adapt to heavier motor oil. Warming up the vehicle fully allows the oil to heat and coat engine parts effectively.

Though the engine typically uses lighter oil, it can adjust. Heavier oil won’t be too thick or sludgy, allowing smooth operation of engine components.

Imbalanced air-fuel mix

Knocking can occur if the air and fuel mixture in the combustion chamber is off. This could point to faulty sensors or injectors.

If sensors fail to detect proper air and fuel levels, a mechanic or you can check the vehicle’s diagnostic system for more details.

Old motor oil

If dirty, old oil is causing the knocking, an engine flush is needed. Dirty oil can hinder small and large engine components. An engine flush should be performed every 12,000 to 15,000 miles.

Final thoughts

Engines may produce knocking noises in winter for various reasons. To identify the exact issue, have a mechanic inspect your vehicle. An incorrect air-fuel mixture might indicate sensor problems.

If dirty oil is circulating in the engine, an engine flush may be necessary. For sticky valve lifters causing the noise, use specialized cleaning products.

Older vehicles with aging engines often knock in winter due to reduced efficiency. Regular maintenance is key to keeping an old car running smoothly.