1998/02/09 Caterpillar

793 (3SJ) 793B (1HL),
793C (4AR) Off-Highway Trucks

Description of Change: Several changes have been made to the Smart Wastegate within the exhaust bypass group that will result in improved reliability, performance, and serviceability. These changes include:

* An improved air supply hose material to provide higher temperature capability.

* A larger diameter air supply hose to provide a greater quantity of air to the exhaust bypass valve (wastegate) (A). This results in improved wastegate performance and response.

* The wastegate solenoid valve manifold (F) is reoriented to a more vertical position to reduce the potential for contaminant buildup. Contaminant buildup can result in poor wastegate performance. Also, the reoriented manifold allows the use of larger air ports (already in the manifold) which lower the restriction to air flow.

* The air supply hose that formerly ran between the cab and the wastegate solenoid has been split at the engine/machine interface (B) to provide improved serviceability. The section of the hose that goes between the engine/machine interface and the cab is part of the brake control group.

Adaptable To: The new components in the 121-5800 Exhaust Bypass Group are identified in the chart and illustration. The new 6J-7777 Hose Assembly has been added to the 124-7690 Brake Control Group. This new hose runs between the cab and the engine/machine interface bracket (5). The new components identified in this article are effective with 3516B (7TR441) Engine in the 793C Off-Highway Truck. The new components are also effective with 3516 EUI (2PK1514) Engine and Remanufactured 3516 EUI (7CL502) Engine for the 793B Off-Highway Truck. When used together, all the new components are adaptable to all earlier 793C, 793B and 793 Off-Highway Trucks with a Smart Wastegate.

The illustration shows the new orientation of the 3E-3510 Manifold (F). The manifold must be positioned so:

* The 109-4591 Solenoid Valve Group (D) is nearly upright.

* The manifold part number (3E-3510), which is stamped on the manifold, must face toward the turbocharger support frame (C).

Formerly, the air supply was connected to manifold port "P". Manifold port "P" is now unused and can be plugged. The air supply is now connected to an unlabeled port. Hose assembly (E) is still connected to manifold port "E" as the air outlet port.

Location of new components in the 121-5800 (793C) and 117-0062 (793B) Exhaust Bypass Groups. Wastegate (A). Engine/Machine Interface (B). Turbocharger Support Group (C). 109-4591 Solenoid Valve Group (D). Air Supply Hose Assembly to Wastegate (E). 3E-3510 Manifold (F).