Usage:
3406, 3406B Truck Engines
- SUPPLEMENT: 06/00/90
TRUCK ENGINE NEWS, FEBRUARY 1990, PAGE 1, "Improvements Made To Water Pumps; New Groups/Parts Available For Certain Applications " for 3406, 3406B Truck Engines. Add the following to this article: The 9Y5647 Water Pump Group will NOT be serviced. Instead, the 9Y5646 Water Pump Group, 9Y5652 Adapter and 9M3786, 4K6804, 4F7387 Seals are required.
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A new nonmetallic impeller is used in the water pump groups. The hub of the impeller is chamfered to allow more phenolic impeller material (black or brown plastic) to surround the metal drive splines. See Illustrations 1 and 2. This helps eliminate early hour cure cracking, and reduces bond separation in extreme service applications. The part numbers of the improved water pump groups with nonmetallic impeller have not changed. The new 7C5479 Impeller (nonmetallic) is a direct replacement for the former 5N7438 Impeller which has been canceled. A larger 4M0347 Washer (3) may be substituted in the field for the standard 9M6527 Washer to improve the clamping load on the nonmetallic material of the 7C5479 Impeller. See Illustration 3.
Illustration 1. Comparison of former (left) and new (right) nonmetallic impellers.
Illustration 2. New nonmetallic impeller with chamfered hub.
A new 9Y5647 Water Pump Group is available that uses a 9Y5652 Adapter (cast iron) and 9Y5646 Pump Group. See Illustration 3. This adapter (1) may reduce cavitation erosion when the recommended ethylene-glycol mixture is not used in the cooling system. Coolant conditioner MUST always be used in the 3400 Family of Engines.
The new 9Y5646 Water Pump Group has a cast iron impeller (2). The 9Y5651 Impeller (cast iron) can be used in extreme load applications. The cast iron impeller is a solid iron casting which would eliminate hub separation as a possible problem.
NOTE: The 9Y5652 Cast Iron Adapter is not compatible with the 7C5479 Impeller because of possible vane to adapter interference.
Illustration 3. Location of cast iron impeller and adapter.
The new 9Y5647 and 9Y5646 Water Pump Groups are available for parts service. The 9Y5646 Water Pump Group is available as remanufactured 0R2856 Water Pump Group.