DIY Mechanic’s Guide to Troubleshooting EGR Systems

Owners of diesel-powered engines appreciate their vehicle’s longevity and minimal maintenance. Diesel engines have long been the top choice for those seeking lots of power, high mileage and few issues. But even diesels can run into trouble sometimes, especially if you typically drive short distances at very low speeds where systems like the EGR cooler don’t get fully used. Continue reading

How Does Exhaust Gas Recirculation Work on a Diesel Engine?

closeup powerful diesel engine

What Is Exhaust Gas Recirculation?

Exhaust Gas Recirculation (EGR) is used in diesel engines to reduce harmful emissions of nitrogen oxides (NOx), specifically, nitric oxide, nitrogen dioxide and nitrous oxide. These greenhouse gases contribute to the breakdown of the Earth’s ozone layer and add to increasing levels of unhealthy smog in high-density areas. Continue reading

Demystifying the EGR Diesel System

EGR part in use inside car

If you’re not a car enthusiast, you’ve probably only heard the term EGR when the local mechanic was giving you bad news about the repairs required to fix your vehicle.

It likely went something along the lines of, “Your EGR valve is having problems,” or “You need to change your EGR sensor.”

When it comes to either diesel engines or motors, EGR systems are a key component in increasing gas mileage and lowering carbon and CO2 emissions, all while lowering the working temperature of your engine.

If you like cars, you should know all about the EGR diesel system, how it works, and why it is used in 99% of diesel engines produced by automotive manufacturers.

What Exactly Is an EGR Diesel System?

EGR stands for “Exhaust Gas Recirculation.” Contrary to what you might imagine, this is a very simple process of recirculating part of the exhaust fumes back into the power stroke.

In layman’s terms, it means what would normally come out of your exhaust pipe is sent back into the engine to get burnt again—re-using the same air and diesel a second time around.

Why Use an EGR System?

There are a few different reasons to consider an EGR system. The first reason concerns pollution.

When your diesel engine compresses the diesel and creates combustion, not all the diesel gets burnt off. To avoid excess diesel-infused CO2 from entering our atmosphere, the system is designed to recirculate some of the exhaust.

The recirculated diesel is burned along with the unused diesel to get a cleaner burn, preventing global warming, smog, and a whole host of other environmental problems. This is done by using more of the diesel that would have been wasted out of the exhaust pipe, thus causing less pollution.

close up of used car EGR

It’s Efficient

The second reason for the system is efficiency. With the rising prices of fuel and the costs associated with burning fossil fuels, the less you waste, the cheaper it is, in terms of fuel costs.

The EGR uses less fuel as part of the combustion, as the diesel/air mix is partly used exhaust fumes, rather than 100% fresh fuel. By adding up to 50% exhaust back into the system, you need less diesel to cause the combustion that powers the motor, saving you money and fuel.

Doing this allows the computer to control the heat and get more efficient use out of the engine. This results in a lower running temperature and better efficiency. Consequentially, an EGR is sometimes called an “EGR cooler” when referring to the overall system.

These days, every major diesel car or truck manufacturer is using an EGR system in their engines. Ford introduced it in the late 1970s on their bigger model pickups and commercial fleet vehicles. Since then, all other major manufacturers have incorporated the idea and concept in some form.

With the help of EGR systems, the heavy polluting diesel engines of our youth are now much more environmentally friendly and can produce up to 60% fewer carbon emissions, though that’s still not a mandatory requirement in vehicle and engine production worldwide.

EGR valve isolated

EGR Regulations

EGR systems are regulated and mandatory in most developed countries, including Canada, the U.S., the UK, and Europe. They are not used in older models and developing countries where the rules governing pollution by vehicles are less regulated.

The EGR systems for large trucks and pickups now come with a huge degree of customization based on personal preference and need. In some cases, people opt to add additional aftermarket or performance versions of EGR systems to their trucks, cars, and buses.

Aftermarket performance EGR systems are some of the most sought-after custom jobs that enthusiasts make to their diesel truck engines, and, in most cases, come combined with ram air or super chargers. These systems are specially designed to increase power and/or efficiency.

Final Thoughts

Most diesel engines in the trucks and SUVs we love to drive wouldn’t meet federal pollution and fossil fuel guidelines without their EGR systems. As the world continues to become more polluted, we can still enjoy our big trucks without losing power or having to pay more taxes for our workhorse vehicles.

What fun would your F350 be with a 3.0-liter engine or, worse yet, a fully electric one? It would lack the power required to tow, haul, or move our goods and equipment.

There is nothing more exciting than the throaty growl of a diesel engine as it thunders under the hood of your truck. EGR systems help to make them more efficient, convenient, and responsible to both our pockets and our environment!

What causes an EGR cooler to go bad?


With any car repair it can be difficult to spot the exact reason why any part may have gone out or worn out. With many parts, there are specific reasons that often lead to failure and knowing a bit about these possible causes for failure can help you to keep your car up and running for far longer. With a complicated part like the EGR cooler, there are two or three possible causes for failure and each points to the need for further service of your vehicle.

The first and most common cause is of course restricted coolant flow. This generally happens when there is a blockage or contaminants in the oil cooler. This restriction of coolant makes it possible for the EGR cooler to stop functioning properly due to increased heat that often throws the sensor off. This restriction of coolant is something that should be looked into by a professional mechanic to help rule out any other issues that may be hiding. A restriction in coolant flow can also affect the rest of your engine and may cause overheating and other serious issues that could lead to the need to completely overhaul a system.

Another cause may be that the part has simply worn out or become old. Often times sensors and complicated parts like the EGR cooler are very finicky. This means that they can wear out easily just through normal wear and tear. Also, taking the time to have your car serviced and properly maintained is the best way to insure that parts do not wear out. Often, a mechanic can spot issues before they become major issues making it possible to correct these problems before they cause even more damage to your system that may already be compromised.

How to Install an EGR Cooler in Duramax

Common to both gasoline and diesel engines, the Chevy Duramax uses a valve to drive the EGR (Exhaust Gas Recirculation) Cooler system. Along with reducing exhaust gas temperatures by up to 800 degrees, the EGR cooler also improves gas mileage and greatly reduces harmful emissions. The valve is the most important component and eventually clogs, needing replacement. To install or replace your EGR Cooler valve, follow these steps.

  • Disconnect the negative terminal of your battery to avoid unwelcome shocks.
  • Find the engine exhaust manifold, which will be on the driver’s side of a Duramax engine.
  • Locate and follow the tubing connected to the manifold to the other end. It’s connected to your EGR system.
  • Disconnect the wiring harness. Press in on the release tab. This will unlock the harness.
  • Loosen and remove the clip on the metal tubing coming from the exhaust manifold.
  • You can then take out the EGR cooler valve after removing the Torx bolts that hold it in place.
  • Place the new EGR valve in exactly the same position as the old one, securing it with the Torx bolts.
  • Re-attach and replace the manifold exhaust tubing. Be sure tighten the clasp.
  • Re-plug in the wiring harness, snapping it in place.
  • You can now reconnect the battery cable.

Be sure to test your installed EGR Cooler valve by starting your engine. Listen for moving air. If you don’t hear any vacuum-like sounds, you installed the new EGR cooler valve properly. Your EGR Cooler system–and your Duramax diesel–should now conserve fuel help save the environment.

Is an EGR Delete Legal?

MTU Exhaust Gas Recirculation

MTU Exhaust Gas Recirculation (Photo credit: Tognum: MTU & MTU Onsite Energy)

Truckers have debated the pros and cons of deleting an EGR (exhaust gas recirculation) system for years. However, there is one overriding risky downside to this action.

Deleting any pollution control device, such as an EGR, is illegal. Not only locally illegal, but this is a federal crime. Should your state inspection also test for emissions, you will fail.

Do not dismiss this particular federal crime. The fines for deleting EGRs or other emission control devices are large, sometimes $10,000 or more. While it’s true fines of this magnitude are rare, you’ll enjoy little benefit, except some loss of engine efficiency, by deleting your EGR.

You also must keep your EGR cooler. Make sure it’s working, as some have a tendency to fail, sending a warning code to your truck’s computer. These can be expensive to replace.

While deleting EGR will not recirculate exhaust gases, making more space for clean air in your combustion chamber, is traditional wisdom. However, modern engines, both gasoline and diesel, are often unable to take advantage of this clean air to improve power and efficiency. You may actually endure reduced horse power.

Since the greatest supposed advantage becomes a neutral issue, the risk of illegally deleting EGR makes no reasonable sense.

What is an EGR Cooler?

Exhaust gas recirculation (EGR) coolers are primarily found in diesel engines. Their purpose is to process exhaust gases and lower emissions. They connect the intake manifold to the exhaust manifold and in most vehicles, they are bolted to the side of the engine, usually on the left cylinder head. EGR coolers vary in size and design, depending upon the size of the engine and certain emissions standards.

There are two chambers in the EGR cooler – an outer chamber and an inner chamber. Anti-freeze runs through the outer chamber and the exhaust gases flow through the inner chamber. As they run through the cooler, the anti-freeze cools down the exhaust gases as both are cycled back into the engine. The exhaust gas recirculation cooler can reduce exhaust temperatures up to 1,000 degrees by the time they reach the EGR valve. The most common gas an EGR cooler deals with is Nitrous Oxide (NOx) which forms at high engine temperatures.

When an exhaust gas recirculation cooler fails, the anti-freeze mixes with the exhaust gases and it produces heavy, white smoke that is discharged from the tail pipe. Other signs of a malfunctioning EGR cooler are a check engine light and a failed emissions test.

In addition to automotive engines, exhaust gas recirculation coolers are also using in mining equipment, oil and gas industry pumping equipment and locomotives.

What does an EGR Cooler do?

An EGR, or Exhaust Gas Recirculation valve, halts a portion of the exhaust gas from leaving the vehicle through the tailpipe and reintroduces it into the engine removing from it the nitrous oxide to reduce emissions. The trouble with this process is that exhaust is already hot, and it’s being recirculated into a hot engine. An EGR cooler, then, makes this less of a problem by cooling the recirculated exhaust and NOx before reintroducing it to the vehicle’s cylinders and sending the less offensive emissions out of the vehicle.

The cooled and separated gas mixture is said to increase the vehicle’s gas efficiency and lifespan because a cooler engine has to work less hard to keep all of its moving parts mobile. Most car manufacturers do not publish their findings on the tests they conduct to see ho well engines actually perform with an EGR cooler in place. Two camps have formed on the assumptions that a cooler engine performs better and the engine has to work harder to keep the cooler going and therefore the engine performance isn’t better it’s worse.

While that particular argument rages on, engine manufacturers are testing new models of EGR coolers on newer model cars. One specifically designed for diesel engines is hoped to increase diesel engine’s fuel efficiency and keep the diesel engines cooler. Diesel engines have a tendency to run hotter than standard engines, so this would be quite the boon to the trucking industry.

In the meantime, cars and trucks that are required to meet emissions regulations are equipped with the current working models of EGR valves and coolers. They have been proven to, at the very least, reduce emissions effectively, and since that’s what they were designed to do, they will continue to be installed in all present and future models of vehicles until something better comes along to replace it. California happens to be one of the states that has such regulations, and there are steep penalties and fines if your car or truck doesn’t pass annual emissions testing, cooled or not. Since most cars and trucks sold in these states are previously checked for an EGR and its cooler, only the out of state vehicle owners need to worry.

Reduce Nitrous Oxide Emissions with an EGR Cooler

English: 3 types of combustion chamber for Jet...

English: 3 types of combustion chamber for Jet engine (Photo credit: Wikipedia)

Before you can understand how an exhaust gas recirculation (EGR) cooler helps, you have to know what the EGR valve does. When the EGR system senses back pressure from the exhaust, it channels exhaust gas back into the engine — more specifically, the combustion chamber. This provides several benefits, including better fuel mileage and allowing the engine to warm up faster since the air in the combustion chamber is warmer. At the same time, the recirculated exhaust is cooler than the combustion chamber, so it also cools the engine while increasing the temperature of the gas.

Furthermore, exhaust is used in hybrid vehicles. When the vehicle comes to a stop, the combustion engine shuts off. If the engine is off too long, it gets cold. The exhaust gas keeps the combustion engine from cooling too quickly, thus keeping it more efficient when the hybrid switches from electric to fuel.

When the engine is too hot, the EGR system diverts the exhaust gas elsewhere so the engine doesn’t overheat. Because introducing exhaust gas into the combustion chamber is excellent for the environment in that it reduces the amount of nitrous oxides emitted into the atmosphere, if an engine uses an EGR cooler, more of the exhaust gas can be diverted into the combustion chamber.

Nitrous oxides are created with high temperatures. A vehicle can register exhaust manifold temperatures of 600 degrees Fahrenheit and more. By cooling down the engine with the exhaust gas, the engine puts out less nitrous oxides, which is much better for the atmosphere.

Another benefit of using an EGR system set up with a cooler is that the fuel burns cooler, which means that there is less detonation. Thus, the timing on the engine can be changed to further increase fuel mileage. It also helps keep heat transfer energy loss lower, which means more of the horsepower and torque created by the engine is transferred to the wheels.

By using an EGR cooler, you still get the benefit of warming up the fuel and coolant and cooling off the engine, but because the exhaust gas is cooler than without using an EGR cooler, the engine uses more of the recirculated exhaust in the engine, thus reducing the nitrous oxides emitted into the atmosphere.