What’s the story on piston cooling tubes for Navistar diesel engines?

The AERA Technical Department says that the piston cooling tube design on Navistar DT 466 and 570 diesel engines has been revised, and this information should be considered anytime the tubes are removed for service on engines with a serial number higher than 2,000,000.

The new piston cooling tube is lighter than previous designs while increasing its structural stiffness. The old piston cooling tube mounting bracket was machined from block steel (Figure 1). The new piston cooling tube has a stamped steel bracket (Figure 2) that is available in two different configurations and comes in a kit that also includes a bolt. Do not use an old bolt with the new piston cooling tube.

The new piston cooling tube is a direct drop-in replacement. The old piston cooling tube will continue to be issued from parts service until supply is exhausted.
It is also important to note that the revised tubes now use an O-ring on the underside of the tube mounting area as shown in Figure 3.

CAUTION: Ensure that you select the correct type of piston cooling tube – with knurling or without knurling as shown in Figure 2 – to install in your customer’s engine, or severe engine damage will result.

I have had complaints of a whining noise in customers’ 3.5L GM engines. Any idea what might be causing it?

A whine or rattle noise that occurs on light acceleration and may be more pronounced at start up or after an overnight soak has been reported on 2004 GM 3.5L VIN 6 Engines. The source of the noise may be an interaction between the balance shaft chain and the tensioner. There are two balance shafts in this engine that are driven by the crankshaft to keep the engine running smoothly. This noise may vary from vehicle to vehicle but does not cause any durability concerns.

To cure this problem, GM has designed a new tensioner to eliminate the noise. The tensioner kit, p/n 89017543, consists of oil fed tensioner, longer tensioner bolts, balance shaft drive chain and right side balance shaft assembly. Please note that it is necessary to install the updated balance shaft assembly because it contains an oil feed passage for the oil fed tensioner.

This new tensioner was introduced into production in the mid December time frame. If the customers’ vehicle was built prior to VIN breakpoints 48123220 (Chevrolet) and 48123225 (GMC), installation of the new tensioner kit is recommended.

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