Thinking about buying a used diesel car? It can be asmartmove, offering impressive fuel economy and robust engines. However, like any used car purchase, there are specific things you need to consider when inspecting a diesel to ensure you're getting a reliable vehicle and avoiding costly repairs down the road. This comprehensive guide will help you navigate the world of used diesel cars, covering everything from engine checks to exhaust systems, giving you the confidence to make an informed decision.
All About Buying a Used Diesel Car
Diesel engines have a reputation for beingdurableand fuel-efficient, making them attractive options in the used car market. But unlike their gasoline counterparts, diesels operate with different technologies and thus require a slightly different inspection approach. Before the 1930s, diesel engines were large and primarily used in ships and industrial equipment. Advances during and after World War II made diesel engines smaller and more suitable for use in cars and trucks.
Choosing a diesel-powered vehicle is appealing to those seeking excellent fuel economy, especially on long journeys. For example, diesel engines offer better MPG over gasoline when towing or hauling. Plus, they typically last longer than their gasoline counterparts. Diesels usecompression ignition, meaning they don't rely on spark plugs. Diesel fuel is injected directly into the cylinder, creating more torque. Modern diesel vehicles include advanced technologies such as turbochargers, direct injection, and exhaust after-treatment systems to meet emission standards and improve performance. This advanced engineering adds complexity to the engines.
Therefore, buying a used diesel car requires a detailed inspection to ensure all the components are in good working order. It's all about carefully evaluating its functionality and overall condition.
Benefits of a Used Diesel Car
One of the most significant benefits of owning a diesel car is itssuperior fuel economy, particularly at high speeds. Diesel engines are inherently more efficient than gasoline engines. Due to their design, the diesel engine also typically delivers greater torque, which is the rotational force that moves the car. The result is better performance when towing heavy loads or driving uphill.
For example, a gasoline SUV might get 20 MPG while towing a camper, whereas a diesel truck would achieve 25 MPG or more under the same conditions. Some diesel car models can run for hundreds of thousands of miles with proper maintenance, highlighting their durability. This longevity translates to lower long-term ownership costs if the initial inspection and purchase are handled carefully. This robust construction and fuel economy are desirable traits for many owners.
Independent tests often confirm the increased lifespan of diesel engines, with some manufacturers estimating over 300,000 miles before major repairs are needed. It's important to remember that older diesel vehicles can have less strict emissions, but also lack some of the more complex and expensive emissions control systems that can be problematic on newer diesels. Choosing which type of diesel to purchase depends on your budget and mechanical aptitude.
How to Check a Used Diesel Car Before You Buy
1. Inspect the Engine
Start with a thoroughvisual inspectionof the engine. Look for any signs of leaks (oil, coolant, fuel) around the engine block, hoses, and fittings. Note the color of the fluids. Black can indicate oil, green or orange may be coolant, and fuel leaks might have a distinct smell. Check the condition of the belts and hoses for cracks, fraying, or swelling.
Next,start the engine. Listen for any unusual noises like knocking, ticking, or hissing. These can indicate potential problems within the engine. Let the engine run for a few minutes and watch for excessive smoke from the exhaust. While some smoke is normal on start-up, continuous black or blue smoke can signify issues with the fuel system or internal engine wear. Diesel knock is normal at first in cold conditions, but should quickly dissipate as the engine reaches operating temperature. If it does not, it may need attention.
2. Check the Turbocharger (if equipped)
Many modern diesel cars are equipped withturbochargers, which enhance power and efficiency. Check the turbocharger for proper operation. With the engine running, listen for a whistling or whining sound from the turbocharger. A healthy turbo should spool up smoothly as the engine accelerates.
Inspect the turbocharger hoses and connections for leaks or damage. A failing turbocharger can significantly impact engine performance and fuel economy, and repairs can be costly. Excessive oil consumption can also be indicative of a turbocharger seal failure.
3. Evaluate the Exhaust System and Emissions Equipment
The exhaust system on a diesel car includes a diesel particulate filter (DPF) and, in some cases, a selective catalytic reduction (SCR) system.Check the DPF for proper function. Look for any warning lights on the dashboard related to the DPF. Diesel vehicles often have an indicator telling when the DPF is cleaning, a process called regeneration. If you are test driving a car with a clogged DPF, the warning indicator will be present and limp mode may be activated.
Inspect the exhaust system for leaks, rust, or damage. A damaged exhaust system can reduce fuel efficiency and create emissions issues. For SCR systems, check the DEF (Diesel Exhaust Fluid) level and ensure the system is functioning correctly. If you are in an emissions-testing state, consider the cost of emissions repairs, especially for older diesels.
4. Examine the Fuel System
Diesel fuel systems are complex and require high precision.Check the fuel filterand look for any signs of contamination. Examine the fuel lines and injectors for leaks or damage. Starting problems, rough idling, and poor fuel economy can be signs of fuel system issues.
It's also worth investigating the history of fuel filter replacements, as neglected fuel filters can lead to significant problems with the injectors and fuel pump. These parts can be quite expensive, so it’s crucial to catch any potential issues early. Check for any signs of black smoke from the exhaust, which could indicate over-fueling or incomplete combustion.
Tips Before Buying a Used Diesel Car
Before you commit to buying a used diesel car, there are a few essential tips to keep in mind.Always obtain a vehicle history reportfrom a reputable source like Carfax or Auto Check. This report can reveal valuable information about the car's past, including accidents, maintenance records, and title issues.
It is highly recommended that youhave the car inspected by a qualified mechanicspecializing in diesel engines. They can perform a comprehensive inspection and identify any potential problems that might not be obvious to the untrained eye. Ignoring these steps could lead to significant repair bills down the road. Also, be aware that diesel engines may require slightly different maintenance than their gasoline counterparts, and plan to keep up with this maintenance to prolong engine life.
Common Issues and Solutions
Used diesel cars can come with specific issues that you should be aware of. One common problem is DPF clogging, which can lead to reduced performance and expensive repairs. Ensure the DPF is functioning correctly and that the car is driven in a way that allows the DPF to regenerate regularly.
Another potential issue isinjector failure. Diesel injectors are precision components that can become clogged or damaged over time. Symptoms of injector problems include rough idling, poor fuel economy, and excessive smoke. If you suspect injector issues, have them tested and replaced if necessary. Regular fuel filter replacements can help prevent injector problems.
Finally, be aware of potentialturbocharger issues. Turbochargers can fail due to oil starvation, contamination, or wear. Symptoms of turbocharger failure include reduced power, excessive smoke, and unusual noises. Regular oil changes and inspections can help prevent turbocharger problems. If a failure does occur, professional replacement is typically required.
Conclusion
Purchasing a used diesel car can be a great investment if you know what to look for. By following this guide and conducting a thorough inspection, you can make an informed decision and avoid costly repairs down the road. Remember to check the engine, turbocharger, exhaust system, and fuel system carefully.
Obtain a vehicle history report, have the car inspected by a qualified mechanic, and be aware of common issues and solutions. Doing your homework will help you find a reliable and fuel-efficient diesel car that will provide years of enjoyable driving. Don't hesitate to ask the seller questions and take the car for an extended test drive to assess its performance under various conditions. With the right approach, you can drive off with confidence knowing you made a smart purchase.