3/1/2002
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Tips for completing the job when resurfacing 16.3L Mack diesel cylinder heads
Q Any tips for completing the job when resurfacing 16.3L Mack diesel cylinder heads?
A The AERA Technical Committee recommends that you pay attention to the fire ring grooves on 1990-2000 Mack E9 diesel engine cylinder heads whenever you resurface the head.
This cylinder head incorporates a circular groove around each combustion chamber and a fire ring bead on the cylinder sleeves. The ring should be restored before returning the head to service.
The fire ring groove on the head surface is required to seal this engine’s high combustion pressures and should resemble the illustration shown in Figure 1.
Whenever the cylinder head is resurfaced, the fire ring groove geometry must be restored to a depth of .005-.013˝ (.127-.330 mm). Tooling for machining the fire ring groove is available from Mack Trucks and aftermarket tool manufacturers.
Q Why does the GM 4.3L balance shaft gear have excessive alignment clearance?
A What you think is "excessive" is actually a concession to OEM assembly concerns. The 1992-2001 GM 4.3L VIN W and X engines use a balance shaft assembly located above the camshaft in the lifter valley area. the shaft is driven off a gear located on the camshaft.
Some AERA members have noted an "excessive" amount of clearance between the alignment dowel hole and alignment pin. Actually, this is a normal condition. Although this type of assembly would typically incorporate a snug fit, the three mounting bolts and holes provide sufficient alignment to allow the correct timing of the gear.
The engine manufacturer specification is .0430-.0435˝ (1.092-1.105 mm) clearance at this location for ease of assembly at the factory. A tight fit would only slow down the assembly line. Aftermarket suppliers of this gear are also providing “excessive” clearance between the two components.
Q What could cause coolant aeration on a 1992 Chrysler Caravan 3.0L engine?
A The AERA Technical committee offers the following information concerning air entering the engine cooling system for 1989-2000 Chrysler VIN 3 and S engines. This condition is often diagnosed as a crack in a cylinder head(s) or a leaking head gasket. However, the absence of hydrocarbons in the coolant indicates some other cause.
This engine utilizes a combination of two coolant inlet pipes located in the valley of the block as shown in Figure 2. They connect the water pump to the heater core and the rear of the engine. These pipes Figure 3, are sealed with O-rings that should be replaced every time the components are disassembled. If this happens, air may be pulled into the cooling system.
Q What’s the proper procedure for removing the intake manifold on a GM 3.8L engine?
A The 3.8L GM VIN K engine uses a two-piece intake manifold assembly. It is necessary to remove the upper intake manifold to service the lower intake, because two mounting bolts are located under the upper manifold.
The two hidden bolts are located in the right front and left rear corners of the lower intake manifold shown in Figure 4 by numbers 5 and 7. Attempting to remove the two manifolds as an assembly will damage the lower manifold.
To install the lower intake manifold, make sure to use a locking compound on the bolt threads and to adhere to the minimal torque value used.
- Clean all oil from the cylinder block, heads and the intake manifold sealing the surfaces with a suitable solvent;
- Clean the intake manifold bolts and bolt holes;
- Apply thread locking compound (GM p/n 12345493 or equivalent) to the intake manifold bolt threads before assembly; and
- Tighten the mounting bolts in sequence.
The upper intake manifold bolt torque should not exceed 89 in. lbs. (10 Nm). Be sure to follow the sequence shown in Figure 5 while tightening each bolt.
Note: Lower intake manifolds used from 1995-’98 (p/n 24505728) should be replaced with new manifolds (p/n 24508923) when degradation of the composite material is observed around the EGR stove pipe shown in Figure 6.
Replacement of the upper intake with p/n 17113136 is also necessary when the revised lower manifold is installed.