The EGR cooler is a component used to lower the temperature of the exhaust gases that are recirculated by the EGR system. The EGR system recirculates exhaust gases back into the engine in order to decrease cylinder temperatures and NOx emissions. The gas circulated by the EGR system can be considerably hot however, especially in vehicles equipped with diesel engines. For this reason many diesel engines are equipped with EGR coolers to lower the temperature of the exhaust gases before they enter the engine.
An EGR cooler is a metal device that employs thin passages and fins to cool the exhaust gases. They function in much the same way as a radiator functions, by using the cool air passing through the fins to cool the exhaust gases as they flow through the cooler. When the EGR cooler has any issues, it can cause problems with the functionality of the EGR system. This can lead to performance issues, and even problems with passing emissions standards for states where they are required. Usually a bad or failing EGR cooler will produce a few symptoms that can alert the driver of a potential problem that should be serviced.
1. Engine overheating
One of the first symptoms of a potential problem with the EGR cooler is engine overheating. If the EGR cooler has any issues that restrict the flow of exhaust gases through the cooler it can cause the engine to overheat. Over time, carbon can build up on the inside of the EGR cooler and restrict flow through the cooler. This can cause the unit to overheat, at which point it will not be able to cool the exhaust gases, and the engine will overheat as a result. Engine overheating can lead to knock or ping from the engine, and even serious damage, if the issue is left unattended.
2. Exhaust leak
Another issue of a problem with the EGR cooler is exhaust leaks. If the EGR cooler gaskets fail, or the cooler gets damaged for any reason, it can cause an exhaust leak to develop. An exhaust leak may be heard as an audible hissing or tapping sound coming from the front of the vehicle. This will reduce the efficiency of the EGR system, and negatively affect engine performance.
3. Check Engine Light comes on
Another symptom of a bad or failing EGR cooler is a Check Engine Light. If the computer detects a problem with the EGR system, such as insufficient flow or exhaust, it will set off the Check Engine Light to alert the driver of the issue. A Check Engine Light can also be set off by a wide variety of other issues, so having the computer scanned for trouble codes is highly recommended.
EGR coolers are not found on all vehicles, but for the vehicles that are equipped with them they are critical to the performance and driveability of the vehicle. Any problems with the EGR cooler can also lead to increased emissions, which will be a problem for states that require emissions testing for all of their vehicles. For this reason, if you suspect that your EGR cooler may be having an issue, have the vehicle inspected by a professional technician, such as one from YourMechanic, to determine if the cooler should be replaced.
This article originally appeared on YourMechanic.com as Symptoms of a Bad or Failing EGR Cooler and was authored by Ed Ruelas.