5-111.bk Page 22 Monday, July 10, 2006 2:26 PM EGR Cooler — The cooler (Figure 11) is a stainless steel assembly mounted on the lower right side of the cylinder block. Hot exhaust gases enter the cooler making two passes through the core. Entering gases flow down through the outer core half and up through the inner half to exit at the top. Coolant flowing directly from the water pump makes three passes through the core. Entering at the rear, coolant is channelled forward through the top part of the core, then down and back through the bottom part, and finally up and forward for one more pass through the top before exiting at the front.
This flow pattern achieves the greatest cooling effect while maintaining coolant temperatures below the boiling point. EGR MASS Flow System Tubes and Clamps — A one-piece, 2-inch (51 mm) diameter tube is used to connect the EGR valve to the cooler on the hot side of the system. On the cool side of the system, a 1.5-inch (38 mm) diameter one-piece tube arrangement is used for routing the exhaust gases from the cooler to the mixer tube on the inlet manifold. The upper portion of the one-piece tube is fitted with the EGR MASS Flow sensors that provide system information to the EECU. Current production now consists of a one-piece cool tube arrangement and a revised mounting system (Figure 12).
Hose connections with constant tension-style clamps are used at both ends, eliminating the bellows sections as used with the two-piece arrangement. Coupling adapters are used in combination with the hoses to complete the connections on engines with flange-style cool tube ports on the mixer tube and EGR cooler. On later-production engines, the flange-style tube ports on the EGR cooler and mixer tube are redesigned to accept the hose connections directly, eliminating the need for the coupling adapters. A petcock is located at the bottom rear corner of the cooler for draining the cooler when it is to be removed for service.
While there are no specific service requirements for the cooler, it is essential for coolant quality to be maintained to keep the core from becoming blocked. Also, prolonged idling can cause carbon buildup and blockage within the core and should be avoided. 11 The EGR MASS Flow sensors are an integral part of both EGR gas cool tube arrangements and cannot be removed. The sensors are calibrated specifically to the EGR cool tube and the EGR MASS Flow System module. If replacement is required, the entire cool tube assembly with its integral sensors and connecting harnesses MUST BE replaced along with the MASS Flow System module attached to the back of the EECU cooling plate.
Figure 11 — EGR Cooler Page 22 DESCRIPTION AND OPERATION 1. Coolant Outlet 2. Gas Outlet 3. Gas Inlet 4. Coolant Inlet