How to evaluate a diesel engine.

Knowing what to check will give you a good indication of an engine’s overall condition

An engine inspection may seem a huge task for individuals like me who are not trained in engines/machineries, however after speaking to some thought leaders in the industry, here are some insights that they share, and how they would go about conducting an engine inspection.

1. Dipstick – pull the engine oil dipstick, as you’re looking for any kind of condensation or grey material on the dipstick or underneath the (filler) lid. That would be an indication of water, moisture or coolant in the engine, which could be very serious and potentially damaging the main bearings. If the condition persists, it could be the result of a pin hole in a cylinder sleeve due to cavitation, a failure of the o-ring at the bottom of the sleeve or a head gasket leak.
2. Air Filter – once you have an idea of what things look like inside the crankcase, take a look at what the engine has been breathing. If dirt has been getting into the engine, that is an indicator of serious trouble. Ideally, the primary air filter should trap all the contaminants and everything behind it should be clean. One recommendation from industry experts would be to pull the air cleaner cover off and take a look at the secondary engine air filter, just to make sure everything looks fresh, clean and new. On many occasions, there is a date stamp on those inner filters which allows you to know how long it has been used or their use by dates. Knowing when the last time a filter was changed could be an indicator of the level of maintenance a machine was given by its owner.
3. Cooling System – Check the coolant level and make sure there’s no indication of oil or anything like that in the coolant. Usually, with coolant, oil will float to the top if the engine hasn’t been running. It’ll be evident in the overflow bottle or under the radiator cap. That problem is an indicator of a crack in the oil cooler, which forces higher-pressure oil into the lower-pressure cooling system. *Please ensure that the engine is cold when removing the radiator cap, doing that on a hot engine will result in scalding hot coolant gushing out.
4. Key Start – Once the preliminary checks are done, it’s time to start the engine up and see how it runs. Observe how long it takes for the r.p.m to level out. Does it run rough? Is it missing on one or two cylinders? How long does it crank over before firing? *Usually on electronic engines, extended cranking is an indication of some type of sensor failure, such as a crank position sensor, on older engines, it is due to low compression.
5. Infrared – An infrared non-contact thermometer will help provide a clearer picture of what’s happening inside the cylinders when the engine is running. Use it to check the temperature along the exhaust manifold at each cylinder. You should get fairly even temperature growth along the manifold. As you get closer to the turbo, the temperature will increase. They (cylinder exhaust manifold ports) should heat up relatively evenly. – If they don’t you could have a poor injector or low compression on one cylinder. If you have a poor injector or a poor combustion cylinder, that one exhaust manifold runner will be colder than the rest.
6. Smoke – Watching the exhaust smoke should also provide some useful clues. But what smoke indicates often depends on the age of the engine. With older equipment, you get lots of smoke, usually (with an internal problem). White smoke could be an indication of coolant loss or improper timing. Older tractors will smoke a light blue when they’re cold. Black smoke will be an indication of over fuelling or restricted air. Grey or hazy would usually indicate some type of oil burn off.

On newer Tier 4A and B engines, once they run for 15 – 20 seconds, you’ll see a bright white smoke, which is actually steam. That’s just from the injection of DEF. It’s common and will clear up as the engine warms up.

Check the crankcase ventilation tube on older engines for indications of blow by, which is an indication of cylinder failure or compression loss. But there won’t be an opportunity to do that on newer engines, which recycle crankcase ventilation into the engine intake manifold.

7. Dashboard – Don’t forget to check the dashboard for warning lights. On new engines, you’ll see an engine fault icon. If it is serious, there’ll be an immediate shutdown. The “stop” light will be on. A lot of new engines right now have a lot of system protections to keep that engine from hurting itself.

The biggest thing on new engines is maintenance, if they say to change the coolant every five years or 2,000 hours, they mean it. Whereas on an old tractor it didn’t really matter, on these it does.