Chapter 6: Engine
Open the hood and check the engine – it should be dry. Dust and grime is fine but it should be dry without any visible oil leaks. Look very carefully to see if the engine looks newly washed. The seller could be hiding an oil leak, although this is not always the case. Some people prefer to have the engine bay washed after a service or in preparation for sale.
Carefully (it could be very hot!) check to see if the engine is warm. Sometimes an engine, diesels in particular, can be difficult to start from cold so the seller will disguise this by kindly pre-heating it in advance of your arrival. Unless he has a good reason, an alarm bell should sound if you find the engine warm. We want to experience the car as we would in normal day-to-day driving – from cold, then again after it has heated up. Be wary if the seller doesn’t offer a good reason why the engine is warm. A warm engine could be hiding worn valve stem seals, failed heating plugs (in the case of diesels), or general engine wear which sounds worst when the engine is cold.
Service History
Ask to see the service book which details all the service work carried out on the car. A full and complete service history(if legitimate) is a great indicator that the car has been pampered. Be sure to ask for information on when the timing belt(if fitted) was last replaced. These are typically changed every 60,000miles. Failure of the timing belt normally spells the end for the engine – so be sure to check this out.
Engine Oil Check
Hold the mayo please!
Have a tissue handy and pull the engine oil dipstick out to check the oil condition. See pictures at the bottom of the previous page for typical locations.
The oil should be somewhere between honey-colored (new) and black (old oil). New oil turns black pretty quickly(especially diesel engines), so unless the oil change happened a few hundred miles before, the oil will most likely be dark brown or black. Check the dipstick carefully for a creamy white/beige/brown substance. It can look a lot like regular mayonnaise. This “mayonnaise” is the result of water from the cooling system mixing with the engine oil. It can come from a damaged cylinder head gasket, damaged cylinder head, or damage to the engine block.
If you find any creamy brown substance in the oil system, just walk away. Cylinder head/gasket damage requires a major strip-down of the engine to diagnose and repair the problem. Even if you can finance an engine rebuild, engines with these faults are often never the same once rebuilt.
Engine Water Check
Making sure the engine is cold, slowly open the cap of the engine cooling water cap. The coolant should be between the max and min levels indicated on the bottle and be a clear, green, red, or rusty brown color. Dip your finger inside and confirm that there is no black oil floating around inside. Rub your finger carefully against the side of the bottle to check whether there is oil clinging to the side. Look at the cap also for signs of oil. Oil here could mean a damaged cylinder head gasket, damaged cylinder head, or damage to the engine block. On some cars with automatic transmission, it could also be transmission oil entering the water system at the transmission inter-cooler.
Always err on the side of caution. If you find any oil in the cooling system, just walk away.
Engine Temperature – Keep it cool!
Start the engine & let the engine warm up – this will take at least 10 minutes if the car is taken for a drive or longer if sitting stationary and the weather is cold. Take a look at the coolant temperature gauge. The pointer needle should climb slowly and begin to rest around the midpoint of the temperature gauge. Open the bonnet and check the top radiator pipe(arrowed) as shown.
A hard radiator pipe indicates an over-pressurized water system. This is normally due to a failed cylinder head gasket or cracked cylinder head or block. It is terminal, so if you find this it’s time to walk away.
Engine Temperature
Watch when you are driving to make sure that the temperature gauge stays pretty stationary. It may rise slowly if you climb a long steep hill, but it shouldn’t move more than 5% on either side of the center of the gauge. A gauge which moves to the high temperature or low temperature a lot during normal driving could mean that the thermostat is faulty or that it was removed to disguise an overheating problem. A partially blocked radiator, faulty radiator fan, or faulty fan sensor may be causing the problem. The cylinder head gasket, cylinder head, or engine block may also be damaged.
Blow By – It’s a blow out!
Another item you need to check is the engine blow by. With the engine running, carefully loosen the oil cap. Slowly loosen your grip on the cap so it’s resting on top of the oil filler hole. Check the force of the gas coming out. The cap may bounce around a little, which is normal, but should not be blown off the oil filler hole by the force of the gases coming out. Excessive “blow by” would indicate that the engine is excessively worn.
Engine Summary
Engine Smoke
Smoke Signals
There are five types of smoke which will come from the tail pipe, from the engine burning fuel:
- Normal Grey
- Normal Frosty
- White
- Blue
- Black
Normal exhaust smoke will be a light gray color. On a cold day this smoke may appear a lot, but this a normal result of hot gases from the combustion chamber of the engine coming into contact with the colder ambient air, just like our breath when we breathe on a frosty morning.
However, smoke other than Grey / Frosty type smoke could spell trouble. See the table below:
Engine Smoke Table
Engine Test
Eyes and Ears Wide Open Please! It’s the Engine Test
Get the owner to start the car and rev it a little, while you stand back towards the middle of the car. You will be listening for rattling noises from the engine and at the same time looking at the tail pipe to see the exhaust smoke. I like to use the owner to do this job. If the car is fine, it sets them at ease. More importantly though, it lets you hear unpleasant engine noises more clearly than you would sitting in the driver’s seat.
Start Your Engines
We are looking for a quick straightforward start here. When the key is turned, the engine should turn over and fire into life within four seconds. Any longer than this and we should be concerned Try starting it again – did it take longer than four seconds? If so then it could be a weak battery, starter, motor, or a more serious engine issue. If only the battery is weak, the car will start normally the second, third, and subsequent times if enough time is given in between to recharge the battery (10 minutes should be enough). When the engine starts, listen for any excessive rattles or clanking. A little rattling noise is acceptable during the first 5-10 seconds, but this should disappear once the oil has circulated properly around the top of the engine. Rev the engine a little, up to 2500rpm is enough. Check the Engine Smoke Table to see if the engine is smoking normally. Go to the hood again and look and listen for any vibrations or misfires. The engine should idle and rev smoothly without hesitation – watch for excessive movement in the engine. More than an inch or so and it may need the engine or transmission mounts replaced.
Engine Summary
Next;
Part 5 : Transmission
Index
