Determining the health of an engine, before or after purchase.June 27, 2018
Regardless if it is an engine you already own or are considering the purchase of a piece of equipment some concerns stay the same; the health of the power plant.
Farm machinery and trucks are known for the robust nature of their construction but the ravages of time, hard work and quite possibly some less than sterling owners over the years that did not believe in maintenance, can all take its toll. A beautiful machine with a badly worn engine in many ways is useless and not worth owning.
To avoid potential engine problems or just wanting to know the health of a machine you already own, some simple investigative work is all that is required. The following procedures can be applied when applicable to either gas or diesel engines, regardless of the year or make.
Look, listen, test
Your investigation into the engine’s health or lack their-of begins with a good visual inspection. I am not worried about minor items centered around consumable parts such as the fan belt or battery, these are easily and inexpensively replaced. But these areas are a telltale sign of how the machine was cared for and the mindset of the owner. Corrosion covered battery terminals and a cracked and dry fan belt speak volumes for a lack of maintenance and the mindset of the owner.
Begin with the inside of the tailpipe. Stick your finger in and see how it comes out. Are the carbon deposits especially heavy? This would indicate rich running on both a gas or diesel engine. When an engine is running with a very rich mixture the fuel will wash past the piston rings and into the engine oil, diminishing its lubricity and creating excessive wear of the piston rings and glaze over of the cylinder wall. If the tailpipe has damp and oily deposits that is a sign of oil being pushed past the third ring on the piston or the valve guides. The ideal is to find a minimum amount of carbon (either a gas or diesel) and that it is dry.
Now go over to the engine dipstick and pull it out and look at the oil color and general appearance and level. The color is not a 100% true indicator of things since it can look deceptively dark even on a well- cared for machine.
If the level is low, that too is telling of the care the engine has seen. Take the dipstick and put it to your nose and take a whiff. Regardless of the fuel type you do not want to glean the odor of hydrocarbons. If the tailpipe inspection proved acceptable and the engine oil is fuel laden, then the machine most likely has seen numerous cold starts and short run times which though are not desirable and cause an exponential amount of wear, but should not be a deal breaker.
Another thing to look for at the dipstick is any signs of white sludge/condensation. The same holds true for the backside of the oil fill cap. When moisture mixes with engine oil it produces a milky white scum. It can be indicative of three things:
The engine was cold started often and never brought to full temperature of the engine oil.
The crankcase breather system is clogged and the engine cannot evacuate moisture, pressure and cylinder blow-by.
There is a crack in a water passage in the engine and coolant is mixing with the oil or a head gasket has failed.
If possible, when the oil fill cap is off look inside with a flashlight. You do not want to see a build-up of sludge of any color. If the material is dark in color that indicates very poor oil service and or the use of inferior lubricants. If it is white, then it is caused by moisture.
Inexpensive to replace, my concern being if the engine was used to do some degree of work, a radiator in poor condition would cause it to run hot, especially around the water jacket of the cylinder head cooling the exhaust valve and combustion chamber.
On a cylinder head with pressed-in valve seats this is the scenario to cause a seat to drop from thermal stress, and when it does, destroy the engine. An underperforming radiator is also the precursor to a cracked cylinder head between the bridge area that is separating the intake and exhaust valves.
On a gas engine remove the distributor cap and grab the rotor and try to move it side-to-side. If there is excessive play, then the bushing in the distributor (or magneto) is worn and the engine timing will skew at higher rpm. Again, the appearance and condition of the inside of the distributor or magneto will tell of its service history.
Start the engine and while doing so listen to how it cranks and the sound. Is it smooth and rhythmic? Does it start easily and once fired how does it sound? As soon as it fires does the oil pressure come up quickly and the valvetrain quiet down. If it does not then it can be a combination of either the oil screen being plugged with sludge, the oil pump weak or the bearing clearances being excessive.
With a diesel engine also pay attention to how easily it starts. Is the cranking speed sufficient? If a diesel cranks well but it is hard to fire it usually is due to worn compression rings and or the cylinder wall. If the engine uses glow plugs once timed out, it should start almost immediately. If not the glow plugs aren’t working properly.
Let the engine warm-up and listen to it while also listening to the exhaust note and feeling the pulses with your hand. Is it smooth and rhythmic? How does the exhaust smell? Are the pistons very noisy (slap)? If there is excessive piston slap when cold, the piston-to-cylinder wall clearance is extreme. It will quiet down a little when the engine heats up and the piston expands. How is the oil pressure if there is a gauge and it works?
Now bring the engine speed up. Does anything change? Does it take the throttle smoothly or stumble? Excessive valve train wear usually speaks up right off-idle. If applicable, put the engine under load. How does the clutch feel and the engine take a drive-away load at closed throttle? Are there any strange vibrations or harmonics?
The last step is to evoke science through the use of oil, coolant and hydraulic fluid analysis. There are many good laboratories that specialize in these services and each test is usually around $35.00. The only caveat being all of the fluids being tested need to have accumulated some hours of use on them for the results to be valid.
I especially like the coolant test on a diesel since through elemental analysis it can be determined if cylinder liner cavitation erosion is occurring prior to a pin hole forming in the liner. This test can either add piece of mind or steer you away from the purchase of a potential nightmare.
The engine oil and hydraulic fluid test can be an excellent predictor of a pending failure through excessive wear material and can also detect other foreign material in the fluid such as moisture or cross contamination from other areas, such as engine coolant.
It goes without saying that none of us can predict the future life of an engine, but by spending a few dollars on fluid testing and implementing the things to look for outlined in this primer, you can move forward with confidence, having performed a high level of due diligence. And if you already own the engine, apply these protocols and see how you stand. It is always better to know than to not know. When it comes to engine health, ignorance is not bliss!