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Technical

Highlights

 Printed on Recycled Paper

United States

Environmental Protection

Agency

Air and Radiation EPA420-F-02-035

September 2002

Office of Transportation and Air Quality

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. This fact sheet describes these requirements for several types

of highway and nonroad engines. Separate provisions apply to

rebuilding urban bus engines (pre-1994 model year) and locomotive

engines; these are not described here.

To which engines does this apply?

You will need to meet these requirements if you are rebuilding an engine

that has been certified to meet certain emission standards for the following types of engines and vehicles:

• Heavy-duty highway diesel engines (40 CFR Part 86)

• Land-based nonroad diesel engines (40 CFR 89)

• Recreational and commercial marine diesel engines (40 CFR Part

94)

• Land-based nonroad spark-ignition engines (40 CFR part 1048)

• All-terrain vehicles, off-highway motorcycles, and snowmobiles

The provisions we describe in this fact sheet apply generally to any

certified engine. For heavy-duty highway diesel engines and land-based

nonroad diesel engines, the recordkeeping requirements we describe

start with the model years listed in Table 1. The emission-control information label on each engine shows its model year and size or power

rating.
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What’s 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 assemblies 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 any records.

How do I meet the rebuilding requirements?

You must have a reasonable technical basis for knowing that you are

rebuilding the engine to its originally 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

reasonable 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 the catalytic converter or other aftertreatment device, if there is one.
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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 original 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.

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.

Can I make any changes to improve the engine?

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.

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 level of emission control. Contact us

if this is not clear from the engine’s emission-control information label.
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What records do I need to keep?

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.

Table 1

Implementation Schedule for Rebuild Recordkeeping Requirements

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*The dates shown apply to commercial marine diesel engines. Requirements related

to recreational marine diesel engines (as identified on the emission-control information label) apply two years later.

**Up to half of a manufacturer’s sales of off-highway motorcycles and allterrain vehicles may be uncertified in the 2006 model year. These vehicles will

not have an emission-control information label and the requirements described

in this fact sheet don’t apply to them.

For More Information

See the following regulations for a more detailed description:

• Heavy-duty highway engines: 40 CFR 86.004-40

• Nonroad diesel engines: 40 CFR 89.130

• Marine diesel engines: 40 CFR 94.11

• Nonroad spark-ignition engines and recreational vehicles: 40 CFR

1068.120

The provisions that apply uniquely to rebuilding locomotive engines are

described in Requirements for Railroads Regarding Locomotive Exhaust

Emission Standards (EPA420-F-99-036).

For additional information, visit the Office of Transportation and Air

Quality Web site at:

www.epa.gov/otaq

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You can also contact us at:

U.S. Environmental Protection Agency

Office of Transportation and Air Quality

Assessment and Standards Division

2000 Traverwood Dr.

Ann Arbor, MI

Voice-mail: (734) 214-4636

E-mail: ASDinfo@epa.gov