Used Car Inspection

How to Inspect a
Used Cars Mechanical Condition

How to inspect a used cars mechanical condition...
The 5th of 8 steps in the used car inspection guide.

The fifth step to your used car inspection is the basic mechanical inspection. This is where you get to take a look under the hood and it's good practice to do this car buying inspection before and after the test drive.

Reinspecting after the test drive, will help to show leaks that may have been steam cleaned away and/or just leaks that weren't there before.

The Hood

  • Any noticeable leaks from the engine.

  • Dry rotted belts or hoses.

  • Clean air filter.

  • Obvious signs of damage to spark plug wires.

  • Rust.

    Quick Note: Never Buy A Car With Rust!
    Rust will eat a car from the ground up.

  • Corrosion on the battery.

  • Condition of the battery cables.

    Surprisingly, these have become very
    expensive to replace on newer cars.

  • and Any other very obvious damage or missing parts.

Fluid Check

Look for:

  • Fluid leaks on the ground
    • Coolant = Greenish
    • Engine oil = Dark brown or black
    • Transmission oil = Red
    • Power steering oil = Red
    • Brake fluid = Clear possibly with a hint of brown


  • Oil color and consistency.

    If it's thick, sludgy, watery or there are metallic pieces present stay away.

  • The color of the dipstick.

    If it has a burnt color, this could be a sign of the engine running overheated.

  • Water or coolant on the oil cap.

    Big problems if they are present.

  • The smell of the oil.

    If it smells like gas the car will need a new engine soon.

  • Smoke coming from the oil cap hole while the engine is running. If so the piston rings are worn.
Smaller oil leaks are OK on higher mile or older cars.


  • Remove dipstick and check fluid color. It should be clean and red.

  • Check for a brown color and a burnt smell.

  • Check to see if the fluid is milky.

  • Check for metal pieces in the fluid.

If you find any of the negatives, this is bad news and will more than likely lead to big problems. I'd suggest you find another car.


First off, Never remove a radiator cap while the car is hot! This could to lead to very serious injuries.

  • Remove the "cold" cap and look for any signs of rust on the cap and around the rim.

  • Check around the radiator area for any obvious coolant leaks.

  • Smell for any signs of gas or oil in the coolant. Bad news if they are present.

  • Oil floating on top of coolant. Also bad news. I'd suggest you find another car.


  • Check for rust.

    Yes, get down on your knees and look under the car carefully. With a flashlight preferably. Read Rusty Car Scam.

  • Check to ensure no parts are hanging or held on with a coat hanger.

and Glass

Check all windows and glass for cracks and/or chips.

Now that you've inspected the cars mechanical condition,
What would you like to do next?

< Go Back To Step 4
VIN History Check
|Move On To Step 6 >
Interior Inspection

Or you can...

Review the entire Used Car Inspection guide by returning from -
Cars Mechanical to Used Car Inspection main page

Go to Insider Car Buying Tips home

Share this page:
Enjoy this page? Please pay it forward. Here's how...

Would you prefer to share this page with others by linking to it?

  1. Click on the HTML link code below.
  2. Copy and paste it, adding a note of your own, into your blog, a Web page, forums, a blog comment, your Facebook account, or anywhere that someone would find this page valuable.