Usage:
3408 Truck Engines
Description of Change: The flow control orifice in the coolant lines group is now machined into the temperature regulator housing. Formerly, an orifice plate was used between the oil cooler bonnet and the coolant inlet of the cylinder block. At the same time, the size of the orifice opening is changed from 1.75 in (44.5 mm) to 1.00 in (25.4 mm). The smaller opening and the new location increase the coolant pressure inside the engine, with a slower rate of flow through the radiator. This increases the pressure on the coolant in the engine to prevent bubbles which can cause pitting (corrosion) in the engine. Also, the slower flow rate gives more time for the natural removal of any air or vapor bubbles in the coolant.
Adaptable To: The new parts, used together, are direct replacements for the former parts, and can be installed on all earlier engines. Do not install either of the new parts without the other.
