EGR for Heavy Duty Engines

The EGR system is used on all vehicles for the purpose of reducing nitrogen oxide emissions. The amount of exhaust flow through the EGR is directly proportionate to the cubic inch displacement and compression ratio.

Heavy-duty trucks such as 10-wheel tractors using large displacement engines and running in all climatic zones and altitudes use more sophisticated computers. It’s necessary to determine the amount of exhaust flow into the cylinders necessary to maintain satisfactory emissions under all conditions of load and atmosphere.

Diesel engine design concentrates on torque more than horsepower. And their service life is far superior to that of a gas engine due to the lubricating properties of their fuel, the heavier construction and very high oil pressure. They also have the advantage in fuel economy.

On the flip side, diesel engines run very “dirty” requiring more service than a gasoline engine. Dirty relating to the amount of soot produced. This soot in the exhaust is re-burned in the engine through the EGR system. Due to the high-compression soot contaminates the oil and requires more frequent oil changes.

The type of oil used is another major factor. It must be designed for diesels. Oil changes should be accomplished every 3000 miles or close.

The EGR and oil cooler must be checked for leaks or clogging on a regular basis. If either begins to clog the engine temperature will begin to rise. If this happens it’s indicative of the clogged cooler. This is a repair that must be done as soon as possible. If ignored, you could quickly be looking at a bill sufficient to make your cheese slide off your cracker. EGR coolers

MTU-Motor 12V 1600 C

MTU-Motor 12V 1600 C (Photo credit: Tognum: MTU & MTU Onsite Energy)

have been a problem on diesels for some time and require an after-market solution to correct. The new coolers have aluminum tubing rather than radiator cores and will last much longer and are trouble free.

How to Clean an EGR Valve

egr valve diagram

The Exhaust Recirculation Valve (EGR) is used to reintroduce spent exhaust gas back into the engine’s cylinders to reduce nitrogen oxide emissions.

The more an engine’s ignition timing is advanced before top dead center the more efficient the engine resulting in more power and better fuel economy.

The downside to advancing the ignition timing is the increased cylinder head temperature. At high temperatures nitrogen oxides form, which, when expelled through the exhaust, have a detrimental effect on our atmosphere—Green House effect.

This is where the EGR comes into play. The EGR is designed to re-route exhaust gas from the exhaust manifold, through a steel tube to the EGR. The EGR is generally situated on the top rear of the intake manifold.

Exhaust gas enters the EGR through the metal tube and exits through a hole in the base of the EGR which sits on a corresponding hole in the intake manifold. A tapered plug called a “Pintle” plugs the hole in the base of the EGR when exhaust gas introduction is unwanted.

As engine rpm increases above idle, engine vacuum is directed to the EGR from a computer actuated vacuum solenoid. This causes a vacuum diaphragm in the EGR to lift the pintle off the hole in its base allowing exhaust gas to pass into the intake manifold. The cylinder head temperature is lowered preventing nitrogen oxide.

Carbon from the exhaust tends to plug the hole in the intake manifold and the one in the EGR. Use a wrench and remove the metal exhaust tube to the EGR at the EGR. Pull the vacuum hose off the EGR and remove the two bolts securing it to the intake manifold using a socket.

Lift the EGR off the intake manifold along with the gasket beneath. The gasket is important. If it is broken or torn it must be replaced. Remove the carbon plugging the hole in the intake manifold using a screwdriver or similar device.

Spray carburetor cleaner on the EGR’s pintle to loosen the carbon. Use your fingers to lift the inside diaphragm thereby lifting the pintle out of the hole in the base. Using a small wire brush, clean the pintle of all carbon and spray again to remove any remaining carbon. The pintle should move easily up and down and completely seal the hole in the base.

Install the gasket followed by the EGR valve. Torque the two EGR base bolts to factory specifications that are found online. Connect and tighten the metal exhaust intake tube. Push the vacuum hose on the EGR.