Como avaliar motor de carro usado, antes da compra!

Summary

The video teaches how to evaluate the engine of a used car to avoid costly repairs. It explains how to listen for unusual engine noises, check for issues like stuck valves, and assess carbon buildup. The presenter provides tips for inspecting different parts of the engine, such as the exhaust, reservoir, and the valve cap, and emphasizes the importance of test driving the car. It also warns about potential problems like worn turbochargers, engine leaks, and faulty seals, offering a step-by-step guide to help buyers make informed decisions and avoid expensive surprises.

Takeaways

• 🛠️ Inspect the engine by turning off the air conditioner and listening for abnormal noises, ensuring the motor runs smoothly without fluctuations.
• ⚠️ Be cautious of fluctuating engine sounds, which could indicate valve issues, potentially leading to expensive repairs (e.g., up to R$7,000).
• 🚗 If you hear a dry, grinding noise while reversing, the crankshaft could be loose, leading to costly engine repairs (around R$12,000 to R$15,000).
• 🛑 Check for sludge or a ‘coffee with milk’ appearance under the oil cap, which may indicate a head gasket issue, costing R$2,500 to R$4,000 to fix.
• 🔍 Always inspect the oil dipstick after test driving to ensure no hidden issues with engine cleanliness or oil leaks.
• 💧 Look for water or oil mixing in the engine, which could indicate overheating or head gasket problems, resulting in significant expenses.
• 💨 Check the exhaust for black residue, which is normal, but beware of oily residue as it indicates a problem with the engine’s lower segment.
• 🔧 Carbon buildup in the engine can lead to poor performance, but descaling can fix it. Heavy buildup may suggest neglect and could be a dealbreaker.
• 🔍 Inspect the water reservoir for cleanliness, as dirty or poorly maintained water indicates potential radiator or head gasket issues.
• 🚘 Pay attention to the type of smoke coming from the exhaust: white smoke can be from cold weather or adulterated fuel, black smoke from excess fuel, and blue smoke signals serious engine problems (like segment wear).

Q & A

What is the first step in evaluating a car's engine according to the script?

The first step is to open the car's hood, turn off the air conditioning, and listen to the engine's sound. This helps identify whether the engine is running smoothly or has irregular noises.

Why is it important to distinguish the sound of a three-cylinder engine?

A three-cylinder engine is naturally louder than other engines, so it's important not to confuse its normal sound with a problem. This prevents misdiagnosing a healthy engine as faulty.

What are the signs of a stuck valve in an engine, and what could be the potential cost of repairs?

If the engine sound is irregular, with the engine running up and down in a non-linear way, it could indicate a stuck valve. Repairing this issue can cost around R$ 7,000 or more.

What could a dry, scraping noise in the engine indicate, and what is the potential repair cost?

A dry, scraping noise in the engine could indicate a loose crankshaft or flywheel, which could require significant engine repairs, costing between R$ 12,000 to R$ 15,000 for a three-cylinder engine.

What does finding a mixture of oil and water (referred to as 'coffee with milk') under the engine cap suggest?

This suggests a possible issue with the engine’s head gasket or overheating, which can cause water to mix with oil. The cost to fix this problem could range from R$ 2,500 to R$ 4,000.

How can carbonization inside the engine affect a car, and what are the solutions?

Carbonization indicates that the engine has not been well-maintained, with burnt oil forming a crust inside the engine. The solution is to perform a decarbonization process, which involves cleaning the engine and replacing filters and oil.

What should you check when looking at a car's exhaust system during an evaluation?

Check the exhaust for any oil mixed with soot, which could indicate problems with the engine's lower parts or turbo system. If oil is found, it could mean a costly engine or turbo repair.

What does white smoke coming from the exhaust indicate?

White smoke could indicate that water is entering the engine, often due to a head gasket failure. However, in cold weather or with bad fuel, white smoke can be normal and less concerning.

What could blue smoke from the exhaust indicate, and what is the likely cost of repair?

Blue smoke indicates that oil is burning in the engine due to worn piston rings or cylinder walls. This usually requires rebuilding the engine, which can cost between R$ 9,000 to R$ 15,000.

Why is it important to inspect the car's reservoir when evaluating the engine?

The condition of the reservoir can show whether the car has been using improper fluids like tap water, which can lead to damage in the cooling system, radiators, or even the engine's head gasket.