Under the bonnet

How to check car engine health


CarVeto history checks cannot assure the health of a vehicle engine. Therefore, this section provides a vital step to avoiding an unreliable vehicle and expensive repair bills.

Engine checks only take a few minutes to run.

Begin by checking that the engine is cold or slightly warm, to avoid the risk of injury. If the engine is already hot it is worth asking the owner why.

Ideally, the engine will be stone cold to run the most effective engine checks.


Oil filler cap and dip stick

Open the oil filler cap and notice any creamy or mayonnaise substances on the inside of the cap.

Pull out the oil dip stick, clean with a piece of cloth, dip back into place and pull out once more. Look for the oil level, oil colour or any unusual creamy substances.


  • Expect dark oil on a diesel engine
  • Expect a transparent oil with petrol engine vehicles
    If oil is darkened a little on a petrol vehicle a service may be due – check when the vehicle was last serviced, via the service book.
  • Mayonnaise-type substances in the oil indicate terminal problems


If the oil level is below minimum levels via the dip stick it means the working parts of the engine are not properly lubricated and may lead to significant mechanical issues.

If the oil level is above the maximum levels via the dip stick it may indicate the engine is burning oil and the seller is regularly topping up.


Checking the expansion bottle

Once more, ensure the engine is cool or cold before opening the expansion bottle. Expect a transparent liquid with yellow, pink or blue colouration, that signals antifreeze.

  • Look for white, creamy substances again, similarly to when dipping the oil stick
  • Creamy substances within the expansion bottle or its cap lead to terminal mechanical issues


how to identify if a car engine is reliable


Additional engine checks

Examine the engine block checking for any oil or water leaks. Bend down under the front bumper and look under the engine for evidence of oil or water leaks. Look at the ground under the engine for any dried oil stains that could indicate an oil leak.


Battery check

View the battery to see if it looks recently replaced.

Most batteries last about 5 years. You may also see a battery looking glass that should signal a green colour. A green display indicates the battery is in good condition. A black display indicates the battery is near its end of life.


Final engine checks

Start the engine from cold listening for any churning, chiming, knocking or grinding noises. Anything that sounds out of the ordinary. Problematic engines may make unusual noises from cold.

Whilst the engine is running turn the steering wheel to full lock. Ensure there are no squeaking or whining noises whilst turning the steering wheel. Such noises can indicate a leaky or broken steering rack.

Read our last post about car dashboard warning checks

The team, CarVeto

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