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Turbocharger oil passing and spilling from cylinder head cover-mounted breather on Mack Truck ASET® engines may be an easy repair

Engine Builders: The AERA Technical Committee explains that turbocharger oil passing and spilling from cylinder head cover-mounted breather on Mack Truck ASET® engines may be an easy repair.

The ASET engines exhibit very good oil pressure throughout the operating range, even at high ambient temperatures with hot oil temperatures. Higher oil pressure results in a greater volume of oil to all the parts of the engine. When the engine is not at normal operating temperature, oil drains back to the crankcase more slowly from the turbocharger and cylinder head areas. As a result, during the initial start-up and warm-up periods, these areas can become flooded and result in the following:

Turbocharger oil passing either at the compressor side, turbine or both.
Oil spilling out of the cylinder head cover-mounted breather.

If any of the above conditions are encountered, do not replace the turbocharger or any other component. These conditions can be corrected by installing two spacers under the oil pump pressure relief valve cap (see Figure 1 for part numbers and spacer sizes). Installing these spacers reduces cold oil pressure by approximately 15 psi, but has no effect on hot oil pressure. Tighten the relief valve cap to 100 ft.lbs. (136 Nm).

Engine Builders: The AERA Technical Committee offers the following information regarding a camshaft gear caution on 1996-'99 Ford 3.4L VIN N SHO engines. This gear is pressed onto the camshaft and over time may become loose.

Ford suggests adding Loctite® 294 to the camshafts which may extend the life of the bond between the camshaft gear and the tube. This procedure can only be done to engines that are not experiencing upper end valve train noise. If such noise is present, Ford says the camshaft may need to be replaced.

Measure the gap between the camshaft gear and the camshaft as shown in Figure 2 (Inspection B). The measured clearance must not exceed .047" (1.190 mm) on any of the four camshafts or the camshaft(s) must be replaced. After camshafts have been checked, clean the area between the camshaft and the sprocket using brake parts cleaner or equivalent to remove any engine oil that may be present. Blow the area clean and dry with shop air. This procedure should be performed twice per camshaft to make sure that all residues have been removed.

Apply light heat to each camshaft gear for about 30 seconds and then immediately apply the Loctite to each camshaft as shown below in Figure 3. Make sure that you get all the way around the camshaft gear so that there is a good bond between the gear and the camshaft.

The locking compound will begin to harden in 10 minutes after application. Full strength is achieved in 24 hours of sitting time. AERA members also have reported that centering the loose gear and then permanently welding it to the camshaft has resolved this type of condition.

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