EGR valve | Operation, performance, maintenance, we tell you everything

While our blog — logically — focuses on DPFs and catalytic converters, today it's time for the EGR valve. It is part of your vehicle's pollution control system and is mainly found on vehicles with diesel engines. Made mandatory by European regulations on pollutant emissions, it regularly arouses anger and discontent among motorists who doubt its real effectiveness. If you want to understand why a simple valve arouses so much passion, here is our article on the EGR valve. Between operation, performance and maintenance, we tell you everything.

Role and function of the EGR valve

The EGR (Exhaust Gas Recirculation) valve is a mechanical part that recycles part of the exhaust gases. Located between the intake manifold and the exhaust manifold, it aims to reduce nitrogen oxide emissions, which are particularly harmful to health and the environment.

A valve and a diaphragm make up this assembly. Part of the exhaust gas flows through the EGR valve and is reintroduced into the intake. The other part of the gas continues its way through the exhaust line, undergoes treatment by the DPF or catalyst and finally escapes through the muffler.

The valve opens or closes intermittently, depending on the parameters provided by the solenoid valve. In this way, the EGR valve recycles between 5 and 35% of the exhaust gases by re-burning them. This theoretically reduces the amount of CO2 in the exhaust gases when they mix with the air we breathe.

Effectively cleaning an EGR valve

Calamitous scale

With these little explanations established, you will then easily understand what always ends up happening. Since the EGR valve is a system within which polluting gases flow, it eventually fouls. Fine particles and carbon deposits settle on the part, build up and eventually clog the valve.

If the valve remains in the open position, it will continuously redirect some of the exhaust gases. Your car's injection system will suffer seriously and in turn become clogged. Conversely, if the valve remains closed, no redirection takes place. Your sedan or SUV will then pollute the ambient air more than it should.

Many options for a clean room

How then to effectively maintain an EGR valve ? In the same way as for a DPF or a catalytic converter. Short urban trips at low revs are a pain in the ass for our vehicles, which are only too happy to unleash their horses on large stretches of tarmac. So plan to drive on the motorway fairly regularly to get the engine up to temperature.

What about cleaning ? There are indeed products to clean the EGR valve, to be poured into the fuel tank. If the part is too clogged, a dismantling and a deep cleaning will then become necessary. If, despite all your efforts, the result is not satisfactory, you will most likely have to go through the repair and replacement process. You will then have to pay between £250 and £650 at your garage, including parts and labour.

>> read also: What is a diesel particulate filter ?

How to tell if your vehicle's EGR valve is out of order

We have just explained that the major disadvantage of the EGR valve lies in the fact that it clogs up very quickly. Diesel drivers will not contradict us on this point.

When you say clogging, you say failure to come. You will detect an EGR valve malfunction quite easily. The vehicle suddenly loses power, to the point where it doesn't rev up at all. We'll let you imagine how dangerous this is if this sudden drop in rpm occurs when you're overtaking another vehicle at full speed.

Other symptoms include the car grazing and stalling very often, as well as the release of thick black smoke, far from making you sympathetic to other users of the public space.

In the event of a breakdown, a warning light will adorn the dashboard of your vehicle. Depending on the make of your car, you will see the engine light or the exhaust warning light. The vehicle's operating instructions will then provide you with any clarification you may need.

Removing or overriding the valve

Whether it is fitted to a Clio 2, a Peugeot 307 or even an Opel Zafira, the EGR valve works the same way. The temptation is often great to disconnect it, to condemn it or to dismantle it, pure and simple. No matter what you call this operation, it remains strictly forbidden by law.

Some smart guys don't remove it, but plug it by closing the valve, so that the gases no longer pass through it and go directly out the exhaust system. This is undetectable, even at the technical inspection. However, let's remind these smart guys that they risk a fine of up to £7,500, which gives us food for thought.

Note, however, that this override is not always possible. Depending on the model, the car will fault and display an error code.

The announced turn of screw in 2019 concerning the reform of the technical control is more of an announcement effect than a real threat. Nevertheless, be careful and at Krosfou we consider that an informed motorist is worth two.