You know the scenario – you’ve been in the market for months trying to find the perfect car to build and all of the sudden one pops up in the forums that looks to be exactly what you’ve been looking for. You trip over the dog and step on the cat to get your phone and quickly call the guy selling it and the first question out of your mouth is, “how does it run?”

For some, if the car runs and drives, that’s usually enough to start negotiating on the purchase price; but like many components of a vehicle, problems may not always be apparent on the surface. Unless you plan on pulling the engine and rebuilding it, or replacing it altogether, there are a few things you should check to get an accurate sense of the condition of the vehicle’s engine and to ensure that you can immediately enjoy driving the car when you bring it home.

Check the basics:

  • Look for oil leaks. Is the engine clean and dry, or is it caked with grease and oil? If it’s the latter, the engine may need the valve covers, oil pan and other parts tightened, or seals replaced; not necessarily a red flag.
  • Grab a white napkin and pull the dipstick. If the oil you wipe off the dipstick is clear and clean, you know the engine has been fairly well maintained. However, if the oil is dark brown or black, the engine may need a good servicing; but, if the oil looks like chocolate milk or has any metallic flakes in it, you’re looking at a head gasket failure or damage to internal components, which will be costly to fix.
  • Remove the oil cap and look down into the engine’s cylinder head; you want to see clean shiny metal parts. If the parts hidden underneath look to be caked with carbon, then the motor has probably not been well maintained.
  • Remove the radiator cap. A well maintained engine in good condition would have clean coolant. Any presence of oil in the coolant indicates that either a head gasket is leaking oil into the coolant system, or that the engine has a cracked cylinder head.

Always ask to do a cold start of the engine: Starting an engine cold after sitting a day or two, opposed to warmed up allows you to get a true feel for how fussy an engine might be and lets you see its behavior as it reaches operating temperature. If the fuel delivery system is improperly tuned, it may take a while to get it running, and may mean a tune up or fuel system overhaul is needed. Additionally, when valve guides are worn, or the valve stem seals are bad, oil tends to seep down into the cylinders as the engine sits for a few hours or longer, causing a noticeable puff of smoke at start up – if this happens, the cylinder heads need to be serviced or repaired.

Listen for tapping, pinging or knocking: The presence of any abnormal sound is a sure sign that something is wrong with an engine. However, the cause of a sound can be ambiguous since these symptoms can mean something as simple as a spark plug needing replacement, or something as severe as damaged main bearings. Hearing any abnormal sounds when running the engine should be a red flag to inspect other things.

Bring a vacuum gauge: Simply bring a vacuum gauge and hook it to a manifold vacuum port. An engine in good condition, should maintain a steady vacuum reading when idling. If the gauge is dipping every second or two, the engine may have issues with the fuel delivery system, the ignition, or may just have a vacuum leak somewhere. If the gauge is completely erratic and you can’t seem to get a reading, then the engine likely has more serious problems.

Actually drive the car: To get to know a prospective project car’s condition, don’t be afraid to drive it. This will not only give you a feel for the performance of the car and its engine’s condition, but will also give you a feel for other components like the transmission, the suspension, steering system and more. When driving a car to get a feel for the engine, take it somewhere that you can get it up to speed, such as a highway, so that you can get the revs up and row through the gears. Monitor the dash gauges for any signs of a problem. As you drive, check for acceleration stumbles and flat spots. These are indicative of carburetor or fuel injection system or ignition system problems.

Run a compression a leak down test: It might be difficult to convince a seller to let you test the compression of each cylinder at their home, but if you manage to get the go ahead to do so, or the ok to have a mechanic inspect the engine, these two tests will tell a lot about the condition of an engine. During a compression test, if all cylinders show a close to equal amount of pressure near the manufacturer’s specs, then the engine is probably in good condition and will not require much if any servicing; however if one cylinder is much lower than the rest, it usually means that either piston rings, a head gasket, or valve has failed and will require repair, or an engine rebuild. If you pinpoint a cylinder with low compression, running a leak down test will help pinpoint the cause. Most of the time, If air is escaping into the exhaust system or intake manifold, then the fault is more than likely caused by valve failure. If air is escaping into the cooling system, then the culprit is likely a faulty head gasket or cracked head. Lastly, if air is escaping into the crankcase, it indicates that the cylinder’s piston rings are worn out or have failed.

By utilizing the method outlined above and by bringing a couple essential tools that all car enthusiasts should have in their tool box along for the test drive, its pretty easy to get a feel for the condition of the engine under the hood, and can safeguard you from buying a money pit.

Alyson Yarberry