The valves referred to in the title of this article are no longer new to modern cars. However, they arouse so many emotions among motorists that it is worth once again to get acquainted with their operation and typical faults that contribute to their malfunction.
The EGR valve (Exhaust Gas Recirculation) is the most important element of the exhaust gas recirculation system. Its primary task is to reduce the amount of oxygen supplied to the combustion chamber, while reducing the temperature. This action slows down the combustion process and reduces the emission of harmful nitrogen oxides (NOx). In practice, part of the exhaust gas instead of the exhaust system is directed back to the intake manifold (recirculation) and burns there.
Differently in gasoline – differently in diesel
It turns out that the symptoms of EGR valve malfunction may be different in spark and diesel units. For the former, the engine is usually unstable, and in some cases goes out. In parallel, errors are stored in the controller’s memory resulting from the detection of an incorrect composition of the air-fuel mixture. In turn, diesels are generally free of these shortcomings. Usually, the only symptom of a malfunctioning EGR valve is strong smoke from the exhaust pipe, which manifests itself especially during sharp acceleration.
How to exchange …
The basic premise determining the life of EGR valves is the cleanliness of fuel refueled at the stations. To increase the durability of this basic element of the exhaust gas recirculation system, good quality fuel should be used. Generally, following the above principle, it was accepted to determine the service life of properly operated EGR valves for 2-3 years or a course of 50,000. km. To make a proper exchange, some basic rules must be followed. First of all, the operation is performed with a cold engine. After removing the EGR valve, thoroughly clean its contact surface, and above all remove the remains of the old gasket. Attention! When installing a new valve, only new brand gaskets must be used. It is unacceptable to make additional counterparts or, worse, to unknown origin of sealing pastes. This is particularly important because any leaks at the EGR valve mounting location will lead to irreversible damage in a short time. Usually this is the burning out of the channel – remember that the exhaust gases blow out have a temperature ranging from 400 to even over 600 degrees Celsius, and the latter cannot be sealed anymore. The next step is to correct the threads in the holes (using the appropriate tap). When installing the valve, remember to use only new fastening screws, which must be tightened with the correct torque. The latter should also be smeared with a measure that will protect them against baking (so that they can easily be removed during the next EGR replacement). Once the valve has been properly installed, its function should be checked – preferably during a short test drive.
… and what not to do
Experts categorically advise against complete and permanent exhaust gas blanking, which is to replace the installation of a new EGR valve. This is usually done by applying a similar gasket to the factory one, but without holes, with the plug still attached, to avoid write errors by the controller. However, this operation can have deplorable results, leading to an uncontrolled increase in exhaust gas temperature (in the case of gasoline units) or an excessive increase in harmful particulate emissions (in diesel engines). A less invasive “economical” method to save money that would have to be spent on a new EGR valve is to clean this damaged item. However, experts advise against performing this operation because it guarantees only temporary improvement of performance.