What is an EGR Cooler? Has my EGR Cooler failed?

EmissionsWhat is an EGR Cooler? Has my EGR Cooler failed?

What is an EGR Cooler? Has my EGR Cooler failed?

What is an EGR Cooler? Has my EGR Cooler failed?

The term “EGR Cooler” has and will continue to become more popular in diesel repair shops in the United States and around the world. Many of you may be asking why this is or what does an EGR Cooler do. Let’s answer a few questions:

What does “EGR” stand for?

Exhaust Gas Recirculation.

Why do most of the latest diesel engines have EGR Coolers?

The EPA (Environmental Protection Agency) has continued to tighten it regulations around exhaust emission for diesel engines. Engine manufactures designed EGR systems to recirculate a portion of the exhaust gases back through the engine primarily to reduce NOx (Nitrogen Oxides which are bad for the environment). The EGR cooler is the portion of this system used to reduce the temperature of the exhaust gas before being recirculated into the engine intake air.

Why do EGR Cooler Fail?

An EGR cooler primarily fails by cracking internally. There are no moving parts in an EGR Cooler. An EGR cooler is simply a heat exchanger which exchanges heat from the exhaust air to the engine coolant. One portion of the EGR cooler has exhaust gases flowing through it (latest designs use tubes) while the other portion of the EGR cooler is flooded with engine coolant. After many cycles of heating up and cooling down, the thermal expansion/contraction causes the materials inside the EGR cooler to fatigue and fracture. When this happens, engine coolant mixes with the exhaust stream.

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How do you diagnose a failed EGR Cooler?

There are a few things you can check to determine whether or not your EGR cooler has failed:

  • Check your coolant level. Is there any coolant in the overflow bottle? If your engine is consuming coolant, the EGR cooler may be cracked and leaking coolant into the exhaust system
  • Is there white smoke coming from the engine’s exhaust pipe? IF the EGR cooler is cracked the coolant will leak into the exhaust system and vaporize.
  • Remove the EGR valve. Does the EGR valve look wet, gummed up, or steam cleaned. This may be a result of an EGR cooler problem.


Failures in the emissions systems are often minor at first and snowball into bigger problems over time. Be sure to address any issues with your diesel engine’s operation sooner than later. An inexpensive fix now could save you thousands of dollars later. Diesel Pro offers an extensive line of EGR related products. Be sure to check out our products on our website or call us if you can’t find what you are looking for.