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Exhaust gas recirculation (EGR) - model 3.0 l
 | To perform maintenance on system components required manual vacuum pump with a vacuum gauge. |
Operating principle The principle of operation of the EGR system  | In order to reduce nitrogen oxides in an exhaust system part of exhaust gas is routed back into the engine. The main components are a recirculation valve EGR, modulating valve and thermovacuum valve (TVV) (location of the first two on the engine shown in the accompanying illustration). |
The modulating valve controls the depth of the vacuum applied to the EGR valve in order to maintain a constant level of EGR. At low temperature coolant TVV is closed and shuts off the vacuum to the valve EGR, supports the latter also closed. When the coolant temperature reaches normal operating temperature, TVV opens, providing access to the modulating vacuum valve. Aperture modulating valve is pressed by exhaust gases from the exhaust system and provides or shuts off the air in the vacuum tube valve EGR, thereby controlling the opening / closing of the latter. At low loads and low engine speeds when the pressure of exhaust gases is small, the spring diaphragm overcomes the pressure, opening the air supply. Accordingly, the EGR valve remains closed.
At high load / engine speeds the pressure of the exhaust gas also rises, overcoming the resistance of the spring and the diaphragm blocking the air supply. At the same time on the EGR valve affects the total depth of the vacuum, which raises the level of exhaust gas recirculation. Checking the operation of the system | - Check the condition of all vacuum hoses. Replace defective.
- Start the engine and warm it up to normal operating temperature. With the engine running, the opening-closing the throttle, observing the behavior of the diaphragm EGR. The EGR valve must be opened and closed simultaneously with the damper.
- If the test conditions are not met, check the system components individually.
Check the EGR valve - Stop the engine and disconnect the supply tube from the vacuum valve EGR.
- Connect the hand vacuum pump with a vacuum gauge to the EGR valve and create a vacuum depth of 120 mm Hg. Art.
- The valve must open smoothly and remain open until the vacuum dropped, otherwise it must be replaced.
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Check modulating valve | - Enter the length of the wire of suitable length to the lower fitting modulating valve.
- Lightly press the diaphragm and using a hand vacuum pump to create a vacuum at the top of the valve fitting.
- If the valve does not hold a vacuum, it can be considered faulty.
- Check thermal vacuum valve
- Start the engine from cold. Disconnect the vacuum hose from the top of the union of the modulating valve.
- Put a finger to the open end of the hose and increase engine speed. Vacuum must not be felt.
- Warm up the engine to normal operating temperature. Again, put a finger to the end of the hose and lift turns. Now, the vacuum should be felt.
- If necessary, replace TVV (arrangement TVV on the engine shown in the accompanying illustration).
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Check thermal vacuum valve | - Start the engine from cold. Disconnect the vacuum hose from the top of the union of the modulating valve.
- Put a finger to the open end of the hose and increase engine speed. Vacuum must not be felt.
- Warm up the engine to normal operating temperature. Again, put a finger to the end of the hose and lift turns. Now, the vacuum should be felt.
 | - If necessary, replace TVV (arrangement TVV on the engine shown in the accompanying illustration).
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