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Hey Engine Man: Why Do I Keep Scoring My Engine Cylinders?

Successful Farming magazine Engine Man Ray Bohacz has engine grease and field dirt under his fingernails from a life spent repairing vehicles and running a farm. When he's not busy in the shop, he's working on maintenance articles and videos for Successful Farming magazine and answering questions from readers. 
 
The following is a letter Bohacz received from Jerry Tice:
 
I have an AgroPower 5000 42-hp. diesel that is a three-cylinder configuration. I have just had the fourth cylinder go bad, but unfortunately I never kept tract of which cylinder was replaced as each was replaced by a different mechanic. At least one of the cylinders has gone bad for the second time. The sleeve and piston are deeply grooved vertically. The tractor is 20 years old but used less than 100 hours per year. I change the oil at the start of each year. Can you tell what is wrong from this information?  
 
Response from the Engine Man:
I am not familiar with an AgroPower 5000 tractor. I have heard of an AgriPower tractor but not an AgroPower brand. This may be important since it will determine the engine we are discussing. I believe the AgriPower models were a Fiat and then Zetor, or vice versa.
 
I would like to know the following so that I can be of more help to answer your question:
  1. What are the symptoms that led you to take the engine apart? Smoke? Noise? Oil consumption?
  2. Is any failure analysis being performed by the mechanic or only the parts changed?
  3. Is it a liquid-cooled or air-cooled engine?
In general, scoring of the cylinder wall and piston skirt first presents itself as scuffing that then, over time, leads to scoring. There are a number of main reasons for this to occur which include:
  • Poor fit of piston to bore
  • Wrist pin walking out of pin bore
  • Overfueling
  • Poor oiling of the bore from a failed or stuck ring
  • Excessive heat or, the inverse, too cold when running
  • Excessive lugging
Since the engine is sleeved, it is safe for me to assume that it is liquid-cooled, but I want to make sure. Historically, if cavitation of a wet liner occurs, the cylinder gets pinholes, but it is possible on an engine that has low hours like yours for it to cause scoring too, but that isn't common.
 
If the tractor is running fine, now we can try to determine a reason via coolant and oil analysis, but those fluids would have needed to be in service for at least 25 hours for the test to be valid.
 
Do you have a maintenance question? Email Ray at SFEngineman@Agriculture.com.
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