How do I test if the EGR valve is working?

Start the engine and place a finger on the diaphragm of the E.G.R. control valve while increasing engine speed from idling to 3,000 to 3,500 rpm. With coolant temperature below 30°C (86°F), the valve should not operate; with coolant above 50°C (122°F), it should operate.

What should I check if the EGR valve operates when the engine is cold?

If the E.G.R. control valve operates when coolant temperature is below 30°C (86°F), check the thermal vacuum valve.

Where is the thermal vacuum valve located?

It is mounted on the right side of the intake manifold. It detects engine coolant temperature by means of a built-in bimetal and opens or closes the vacuum passage.

What are the parts of the EGR control valve?

The diagram labels: 1 diaphragm spring, 2 diaphragm, 3 valve shaft, 4 valve, 5 valve seat, and 6 valve chamber.

How does the EGR control valve work?

It controls the quantity of exhaust gas led to the intake manifold through vertical movement of the valve connected to the diaphragm, to which vacuum is applied in response to the opening of the carburetor throttle valve.

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Nissan Micra EGR System Description & Inspection - EGR Valve, Thermal Vacuum Valve

E.G.R. control valve and thermal vacuum valve cross-section diagrams, Nissan EF & EC manual

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EGR control valve and thermal vacuum valve cutaways plus function check; EGR control valve should operate when coolant is above 50C and engine raised to 3,000-3,500 rpm.

AI caption June 2005 · Photo 125 of 412

This is a page from a factory service manual covering the Exhaust Emission Control — E.G.R. (Exhaust Gas Recirculation) System, page EF & EC-25. The left column continues the system description: the E.G.R. control valve regulates the quantity of exhaust gas fed to the intake manifold via vertical movement of a valve connected to a diaphragm, actuated by vacuum in response to carburetor throttle valve opening. A cutaway diagram (EC231) labels six components: diaphragm spring, diaphragm, valve shaft, valve, valve seat, and valve chamber. The thermal vacuum valve, mounted on the right side of the intake manifold, senses engine coolant temperature via a built-in bimetal and opens or closes the vacuum passage; a second diagram (EC232) shows the O-ring, bimetal, and spring. The right column gives inspection procedures for the entire system: visually check hoses for cracks, then start the engine and feel the E.G.R. valve diaphragm. With coolant below 30°C (86°F), the valve should NOT move when engine speed is raised from idle to 3,000–3,500 rpm (illustration SEC140A); with coolant above 50°C (122°F), it SHOULD move under the same test (illustration SEC141A). If the valve operates when cold, the thermal vacuum valve should be checked.

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Frequently asked questions

How do I test if the EGR valve is working?: Start the engine and place a finger on the diaphragm of the E.G.R. control valve while increasing engine speed from idling to 3,000 to 3,500 rpm. With coolant temperature below 30°C (86°F), the valve should not operate; with coolant above 50°C (122°F), it should operate.
What should I check if the EGR valve operates when the engine is cold?: If the E.G.R. control valve operates when coolant temperature is below 30°C (86°F), check the thermal vacuum valve.
Where is the thermal vacuum valve located?: It is mounted on the right side of the intake manifold. It detects engine coolant temperature by means of a built-in bimetal and opens or closes the vacuum passage.
What are the parts of the EGR control valve?: The diagram labels: 1 diaphragm spring, 2 diaphragm, 3 valve shaft, 4 valve, 5 valve seat, and 6 valve chamber.
How does the EGR control valve work?: It controls the quantity of exhaust gas led to the intake manifold through vertical movement of the valve connected to the diaphragm, to which vacuum is applied in response to the opening of the carburetor throttle valve.