How to Maintain or Rebuild Engines
Certified to EPA Standards
The U.S. Environmental Protection Agency (EPA) has adopted
requirements that apply to the process of maintaining or rebuilding
engines. These requirements generally describe how to avoid violating
the prohibition against tampering with a certified engine; it therefore
applies broadly to all types of certified engines and vehicles. Separate
provisions apply for rebuilding and remanufacturing locomotive engines
and some marine diesel engines.
What is the general principle behind EPA's rebuilding requirements?
As someone who maintains or rebuilds engines, you must generally restore the engine
to its original configuration. This keeps the engine running the way the manufacturer
originally designed it to operate, both for controlling emissions and for achieving the
best overall performance. This adds an assurance that each engine will continue to
control emissions, consistent with the manufacturer's original design, throughout its
lifetime.
What does EPA consider "rebuilding"?
Rebuilding refers to a partial or complete rebuild of an engine or engine system. This
includes a major overhaul in which you replace the engine's pistons or power assem-
blies or make other changes that significantly increase the service life of the engine.
It also includes replacement or rebuilding of an engine's turbocharger/aftercooler
system or its fuel injection/electronic control system if it increases the service life of
the engine. For these provisions, rebuilding may or may not involve removing the
engine from the truck, equipment, or vessel. Usually rebuilding does not include
following the manufacturer's maintenance instructions or other routine maintenance;
for these simpler service items you still need to avoid making changes that might
increase emissions, but you don't need to keep records.
SEPA
United States
Environmental Protection
Agency
Office of Transportation and Air Quality
EPA-420-F-12-052
August 2012
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How do I meet the rebuilding requirements?
You must have a reasonable technical basis for knowing that you are rebuilding the engine to its
original certified configuration for all the relevant tolerances, calibrations, and specifications that
might affect emissions. You may use new, used, or rebuilt parts, but you should have a reason-
able technical basis for knowing that the parts perform the same function as the original parts.
You should follow the original engine manufacturer's instructions if you change any parameter
or design element. Also, be sure to check, clean, adjust, repair, or replace all critical emission-
related components as needed according to the original manufacturer's recommended practice.
This includes any installed catalytic converters or other aftertreatment devices.
What is a "reasonable technical basis"?
You have a reasonable basis if you do two main things. First, you must install parts (new, used, or
rebuilt) so a person familiar with the engine's design and function would reasonably believe that
the engine with those parts will control emissions to the same degree as with the original parts.
For example, it would be reasonable to believe that parts performing the same function as the
original parts (and to the same degree) would control emissions to the same degree as the origi-
nal parts. Second, adjust parameters or change design elements only according to the original
engine manufacturer's instructions. Or, if you differ from these instructions, you must have data
or some other technical basis to show you should not expect in-use emissions to increase for any
pollutant.
What about diagnostic codes in the engine's computers?
Don't erase or reset emission-related codes or signals without diagnosing and responding
appropriately to the diagnostic codes. Clear all codes from diagnostic systems when you return
the rebuilt engine to service. Don't disable a diagnostic signal without addressing the problem.
This doesn't apply to an engine if it has no onboard computer.
May I make any changes to improve the engine?
a
Yes. You may make changes if you have data or some other technical basis to show that emissions
will not increase. Also, you may use different than original parts or make other adjustments if
they make the engine operate like one of the engine manufacturer's newer certified models.
Does the rebuilt engine need to meet emission standards?
There is an expectation that the engine will continue to meet the emission standards that
applied when it was new, as long as it is restored to its original configuration. Rebuilders do not
need to perform emission testing to demonstrate that rebuilt engines meet emission standards.
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In the case of locomotives and some marine diesel engines, additional requirements apply when
engines are remanufactured. Under the regulations, remanufacturing is a type of rebuilding that
generally involves replacing all of an engine's cylinder liners, whether during a single maintC'
nance event or cumulatively within a five-year period.
May the rebuilt engine go into any vehicle, equipment, or vessel?
No, some restrictions apply. Rebuilt engines should return to the same type of service (highway,
nonroad, or marine). Also, the engine may not go into trucks, equipment, or vessels that
were originally powered by engines certified to a more stringent standard. Contact us at
complianceinfo@epa.gov if this is not clear from the engine's emission control information label.
What records do I need to keep?
Recordkeeping requirements apply for rebuilding heavy-duty highway engines and any types of
engines or vehicles that are subject to 40 CFR part 1068. However, the regulations waive the
recordkeeping requirement for all nonroad spark-ignition engines with total cylinder displace-
ment below 225 cc. Keep the following records for at least two years:
• the hours of operation (or mileage or other indication of age) at time of rebuild
• the work performed on the engine
• emission-related control components you worked on, including a listing of parts and
components you used
• engine parameter adjustments
• emission-related codes or signals you responded to and reset
You may keep records based on engine families rather than individual engines if that's the way
you do business. Keep the records in any format that allows us to review them if we ask. If you
are a "backyard mechanic" working on your own engines, we don't require you to keep any
records.
What records are not required?
You don't need to keep information that is not reasonably available through normal business
practices. We don't expect you to have information that you can't reasonably access. Also, you
don't need to keep any records of what other companies do.
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For More Information
See the following regulations for a more detailed description:
Nonroad engines and vehicles: 40 CFR 1068.120
Heavy-duty highway engines: 40 CFR 86.004-40
You can access documents related to emission standards for nonroad and highway engines on
EPA's Office of Transportation and Air Quality (OTAQ) web site at:
www.epa.gov/otaq/
You can also contact the OTAQ library for document information at:
U.S. Environmental Protection Agency
Office of Transportation and Air Quality Library
2000 Traverwood Drive
Ann Arbor, Michigan 48105
(734) 214-4311& 214-4434
Email: Group_AALibrary@epa.gov
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