Breaking in your New or Rebuilt Engine

The term “breaking in your engine” is a term used in our industry during the initial startup and run time of your engine.  This is where all the hard work and money you have invested comes together in a mechanical symphony.  This is a crucial time to check pressures and look for leaks, but what about everything going on inside the engine.  In this tip we will go over some of the key points on what to do when you are ready for initial startup as well as what other important habits you need to perform that will guarantee your engine is in top shape.

Break In Oil

We covered this a little more in depth in Tech Tip #25:  Break-In Oil; Why Old Is Better, but so we won’t  “beat a dead horse” more than needed other than to say that the  initial oil you run your engine on for the first 200 to 500 hours is extremely important.  Be sure that you are using the right stuff.

Initial Startup

This is usually the make it or break it moment.  I would consider this to be the first hour or so of engine run time, because most engine build issues arise during this period.  If you make it past this stage, you are generally less likely to experience any issues due to workmanship or defective part failures.  During this time, it is important to closely monitor coolant temperatures and oil pressures.  It is also good to “heat cycle” the engine a few times. Heat cycling is letting the engine get up to operating temperature and shutting it down to cool off. This lets all the engine parts expand and contract to find their sweet spot and stay there.  It is also a good time to run the engine at specific RPMs for different durations during this process. This helps to move oil into the galleys at different pressures allowing trapped air pockets to escape. It also helps to simulate operation of the machine without adding a load to let friction surfaces have a chance to show a problem, if there is one, without having a catastrophic failure. It’s better for you to find the problem now and have a chance to fix it rather than putting a hole in your engine block!   Lastly, change your oil filter and oil after the initial break-in period.  During the rebuilding process we all try to keep a clean work area and do our best to keep all the parts clean as well.  This isn’t a perfect world, and things happen that we all miss. Changing your oil after you pass this stage will allow any dirt or oil contamination to leave the engine, it will also help remove any wear metals that might have occurred during this time.

The Break In

This is the time frame that will determine how well your engine will run and will often change how often it might have issues as well.  You will hear several stories when you ask this question to the “ole timers”, some will tell you to only push it a little, others will tell you to push it in waves. Me, I say give it the hurt.  Now I am not saying to start the engine up and put it under full load.  Always do the proper warm up procedures for your engine; this is important.  What I am saying is don’t just sit there and idle, put it to work.  During the break in stage, your break in oil works in tandem with your freshly built engine.  Lubrication is being distributed, chemistry is happening with the additives in the oil, and the piston rings and cylinder walls are wearing to perfection.  Without the right conditions, these will not happen properly.  The most common among the things that you want to happen during the break-in is the “seating” of the piston rings.  Thought you should have “seated” the piston rings in the piston when you installed them, the term comes from the process of the rings wearing into the cylinder walls during the break in.  The hone pattern on the cylinder walls is responsible for helping to hold the oil for lubrication, while the lower piston ring is responsible for removing some of that oil, so it does not get consumed during combustion.  If the piston rings do not “seat” the walls of the cylinder can hold too much oil and the lower piston ring can’t keep up.  This causes excess oil consumption.  By putting the engine under a load, you are heating the piston rings forcing them to expand into the cylinder wall which helps to wear down some of the cylinder wall thus keeping it from holding too much oil, this is seating the rings.  Failure to do so can result in major oil consumption which can wreak havoc on other engine components. In the long term, it can even cause premature engine failure.

Now you might ask why this can’t be done prior to assembling the engine, and you would be right to ask.  It can be done, it is called “hone lapping” and it is a process that benefits many newer engines.  There are also different styles of honing, such as helical slide and plateau honing. All which assist in different ways to reduce oil consumption but may require the use of special “keystone” piston rings.  If your engine was not designed to work with these newer styles of honing, it would probably be best to stick with what you know is right. Your engine parts are designed to work with each other and changing something, no matter how small, can affect your engine in ways you might not have considered.

In short, be mindful of the fact that breaking in your engine properly is an important step in what should be a long life for your new engine.  Excessive idling and light loading are unhealthy for your engine, and not just during the break-in, but throughout the engine’s life.  Be mindful that monitoring engine temperatures and pressures and responding to them when irregularities first come to your attention, can allow you to solve a problem before it becomes catastrophic.  And providing your engine with regular care and maintenance after a proper break-in should have your engine running at its best for a very long time.