Clogged EGR valve: Symptoms and what to do


What is the EGR valve?

The EGR valve is a component that serves to reduce the emission level of modern vehicles. This valve recirculates part of the exhaust gases back into the engine (between 5% and 15%). This allows complete combustion of the fuel and a reduction of toxic substances, including nitrogen oxide.

Some vehicles have a mechanical EGR valve, actuated by the gas flow, while others have an electronic one. Generally, the electronic versions, like all other components, tend to give more problems in the long run.


EGR stands for Exhaust Gas Recirculation.

The EGR valve is almost always fitted to almost all diesel engines and more and more recently also to petrol engines.

Car EGR valve indicator light: what is it?

The EGR valve does not have a dedicated indicator light itself, but any problems are indicated by the general engine fault light. However, newer cars, in addition to illuminating the general engine fault light, will indicate on the digital display or in a code or directly the cause of the problem, in this case the EGR valve.

The general engine fault warning light is the red one that represents an engine. If you are unable to recognise it, we recommend you take a look at our Guide to Car Indicators.

What are the benefits of a good EGR valve?

In addition to lessening the environmental impact of our driving, a fully functioning EGR valve in good condition also benefits the driver. We see all the benefits of a well-functioning EGR valve:

  • Increased enginelife - by helping to lower the temperature inside the engine, the EGR valve contributes to the longevity of our engine. Specifically, the EGR valve helps keep the cylinder valves at a lower temperature, resulting in lower thermal stress and longer life.
  • Fuel economy: If the EGR valve becomes clogged, which happens after thousands of miles, combustion will be uneven and more fuel will be consumed. To keep the engine in a state of perfect efficiency, don't underestimate or forget the EGR valve.
  • Fewer emissions - in the end, the EGR valve is a mechanism designed to reduce emissions. If it becomes clogged or damaged, it stops performing this task and we risk driving and polluting much more. Unfortunately, many people don't care about the environment, but it may interest you to know that emissions are measured during the ministerial test. If the EGR valve is not working properly, the emissions will be too high and you will most likely fail the test. To find out about all the other checks performed during the service take a look at this article.

Symptoms of a broken or clogged EGR valve?

Like all car components, EGR valves are subject to wear and tear and can therefore break. Because they deal with exhaust gases, they can become clogged and clogged in the long run, becoming partially or completely non-functional. Let us now look at the possible causes of EGR valve failure:


  1. Increased particulate matter in the exhaust gas - if the EGR valve becomes blocked or clogged, it could remain open and increase the number of particulate pollutants and unburned fuel in the exhaust gas. A pretty clear symptom is if we notice that more black liquid is coming out of our car's exhaust pipe than usual. A few drops can only be dirty condensation, but a constant drip is a symptom of a clogged EGR valve.
  2. Difficulty starting the engine - a faulty EGR valve that remains open can create a vacuum leak inside the intake manifold, leading to problems starting the engine.
  3. Loss of power at low revs - if the valve cannot close because it is clogged or broken, the engine will not be as efficient as under normal conditions.
  4. Engine knocking - if an abnormal amount of exhaust gas is recirculated, the combustion of the engine may not be correct and cause knocking. Usually this sound is due to the fact that some of the fuel remains untapped and is recirculated too soon.

What problems does a broken or clogged EGR valve cause?

If the EGR valve is broken or clogged, the following scenarios can occur:

  • The EGR valve remains open - in this case the engine receives less fresh air and combustion problems and increased wear of internal parts can occur.
  • The EGR valve remains closed - in this case the engine is not running as efficiently as possible and emitting more pollutants into the atmosphere.

How much does it cost to replace the EGR valve?

If an EGR valve is too clogged or damaged after years of wear and tear, replacement becomes the only possible option. Fortunately, this component is quite inexpensive, usually between 50 and 70 euros.


If we then rely on a specialist garage, the price of the EGR valve will be added to the cost of the garage's labour. Normally a good mechanic should not take more than two hours. Calculating an average labour cost of 40 euros per hour, the replacement of the EGR valve should cost us a total of about 150 euros.


What to do if the EGR valve is dirty?

It can often happen that the EGR valve is only very dirty and not necessarily damaged or broken.

In this case we can also avoid replacement and opt for the much cheaper cleaning procedure.

To clean the EGR valve you need to buy an EGR valve cleaner, making sure it is specific to your car. There are several versions in circulation, some suitable for diesel engines and others specifically for petrol engines.

You can buy the EGR valve cleaner from both physical stores and the various online accessory sites. The cost of the cleaner is usually around 15-20 euros.

The EGR valve cleaner acts on the dirt and revitalizes the valves by removing scale and exhaust residue. What's great is that you don't even need to remove a single screw, the cleaner acts as a closed loop cleaner and greatly reduces costs.

Another advantage of using the cleaner is that it restores normal exhaust gas flows, reducing fuel consumption and increasing the car's performance. In addition, the cleaner greatly reduces the residual smoke that we normally see coming out of the muffler.



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