5-111.bk Page 21 Monday, July 10, 2006 2:26 PM EGR Valve — The poppet-type valve, operated by hydraulic pressure from the engine oil system, meters exhaust gas from the exhaust manifold into the EGR circuit (Figure 9). The hydraulic pressure is controlled by a solenoid within the valve assembly reacting to signals from the engine EECU. An internal spool valve diverts hydraulic fluid, applying pressure to precisely position the EGR poppet valve for control of exhaust gas circulated through the engine. The poppet valve has two sealing surfaces on a common shaft to draw gases from the front and rear sections of the manifold simultaneously.
For current production (starting in March 2004), the design of the EGR control valve shaft seal has been changed to prevent contaminants from entering and damaging the oil seal. Additionally, a filter screen has been added to the oil inlet port (Figure 10). The screen and a wave washer are retained in the inlet port counterbore by the oil inlet fitting. 10 The center section of the exhaust manifold (Figure 15) is redesigned with mounting surfaces for the EGR valve and turbocharger. The valve, which is mounted on top the center section of the manifold, is a non-serviceable unit. If a failure should occur in any part of the valve, the valve must be replaced as an assembly.
9 Figure 10 — EGR Valve Oil Inlet Filter Screen Figure 9 — EGR Valve Page 21 DESCRIPTION AND OPERATION 1. O-Ring 2. Fitting Jam Nut 3. Integral Washer 4. Valve Body 5. Part Number Location 6. Filter Screen 7. Wave Washer 8. Oil Flow Direction