EGR – What is it? How does it work?

EGR – stands for Exhaust Gas Recirculation

EGR Valve and EGR system defined

The EGR valve is part of the EGR system. The EGR valve is controlled by an onboard computer system that tells the valve when to open, close and controls the flow rate of the valve as well. The EGR valve opens and closes to allow exhaust gases to flow back into the intake system. The gases make their way into the combustion chamber and act as inert gas to lower the combustion temperatures. The EGR valve is not constantly working and opening and closing all the time. On most vehicles, under heavy load and high RPM your EGR valve will not be opening. The purpose of the EGR system is to reduce or almost eliminate the amount of NOx your vehicle emits into the air we breathe.

Nitrogen and Oxygen combine at about 2500 degrees or higher creating NOx. If the combustion chamber reaches over 2500 degrees, the left-over gases inside the chamber combine and create smog or NOx. NOx is the low hanging smog you see in the air. The EGR system was designed to reduce the temperature inside the combustion chamber, so NOx is not created, and all the excess gases are burned off vs being released into the air.

Today, most modern Diesels tend to have EGR Coolers. EGR Coolers act like a radiator, the cooler has coolant in it which sucks the heat out of the air coming from the Exhaust system. This is an extremely important process because the exhaust coming out of the manifolds can be extremely hot. If this air is not cooled before entering the intake, then the extremely hot air could create more NOx to be released into the air instead of reducing the amount of NOx released.

Diesels more than gas vehicles tend to have problems with their EGR system because Diesels have what is called soot. Have you ever been driving down the road and you see a Diesel drive by and accelerate and a puff of black smoke can be seen coming out of the tailpipe? That black smoke is the “soot”, this can typically be seen in older Diesels because they do not have as many, if any, emissions control components.

Although some older Diesels could have EGR’s the EGR systems did not really start being installed on Diesels till about 2001. Newer Diesels have what is called a Diesel Particulate Filter. This filter captures the soot and does not allow it to be released into the atmosphere. If your Diesel Particulate Filter gets plugged up, then the soot will flow into your EGR Cooler. The EGR Cooler can then get plugged up with soot which will cause your EGR valve to stop working. Diesel Fuel Additive can help reduce the amount of soot your vehicle puts off which can assist in keeping your vehicle running well. Using Fuel Additive appropriately can help drivability, and your fuel and exhaust systems and even help your fuel economy. Fuel Additive will be further discussed on our website under Fuel Additive.

Some common problems we see with EGR Systems and EGR Valves

  1. Insufficient flow from EGR Valve
  2. EGR Coolers can break and crack open causing coolant loss, overheating, and engine failure.
  3. Diesel may run poorly if there’s a problem with your EGR Cooler
  4. Lack of performance
  5. Lack of boost

Plugged up EGR CCoolers and Valves can cause all kinds of problems.

***These problems ARE going to happen to every Diesel from the begining of the 2000’s and newer. Why? Because the EGR Valves, EGR Coolers and Diesel Particulate Filters are added on components tp lower emissions output***

 The parts that comprise an EGR system in a Diesel are:

  1. Cooler, Cooler Bypass Valve
  2. Pipes and plumbing between Cooler and exhaust, and Cooler and EGR and EGR to the Intake.
  3. EGR Valve
  4. Electronic Throttle
  5. Vaiable Turbo

***The components and parts in YOUR EGR system can differ depending on the year, make, model and manufacturer of your vehicle.***

The only manufacturer that did not change over to the EGR stsyem in the early 2000’s was Cummins. Cummins dud not add the EGR system till about 2007 when they came out with their 6.7L Diesel. The 5.9L Cummins and 7.3L Diesels did NOT have an EGR Valve. Cummins had to add the EGR System to stay within the EPA regulations when they came out with their 6.7L Diesel.

Is there any preventative maintenance I can do to preserve the life span of my EGR Cooler to help prevent major repairs?

Preventative maintenance as a good rule of thumb is a service not a repair for a problem you are already having. A few things you can do to preserve your EGR system and components is:

  1. Use Fuel Additive APPROPRIATLY
  2. If your Diesel has a Diesel Particulate Filtere, proper vehicle maintenace in acvordance with the manufacturer scheduled maintenance is CRITICAL! Fluids and filters will effect combustion efficiency and effect the DPF.

PLEASE NOTE: Driving habits can also affect the life of your EGR components

*** EGR systems on Diesel vehciles use EGR Coolers to cool the exhaust gases, most gasoline vehicles do NOT use EGR Coolers.***

If you have a question about your Diesel or EGR system, we at Champs Family Automotive are always here to help. Feel free to call either our Surprise 623-376-6791 or Gooyear 623-882-8200 shops at your earliest convenience.