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The following technical bulletins were published by AERA.
 DISTRIBUTOR GEAR WEAR
                                             Distributor Gear Wear On
                                  GM 4.1L (HT-4100 Cadillac) Engines

Premature distributor gear wear has been noted on GM 4.1L (HT-4100 Cadillac) engines.

Since there is no direct lubrication of the distributor gear, General Motors has revised the gear to help eliminate this problem.  The revised gear carries GM Part #10499813 and can be identified by a cut ring on the body section of the gear.

Since the cam bearing housing bores are fully grooved, AERA members have enhanced lubrication of the gear.  Drill a small (1/32) hole from the groove of the last cam bearing housing bore forward toward the distributor opening of the cylinder block. 
Inserting the distributor into the block can be of assistance in locating this hole.

                                                                      The AERA Technical Committee
 REVISED INTAKE MANIFOLD GASKET END SEALS
           Revised Intake Manifold Gasket End Seal On
              GM 4.1, 4.5 & 4.9L (Cadillac) Engines


General Motors Corporation has revised the intake manifold end
gaskets for all of their aluminum V8 engines used in Cadillac
automobiles.  The revised seal features reinforced flanges to
more positively retain the seal in position on the cylinder block
(Figure 1).  A pair of end seals is available under GM Part
#3635212.

The revised seals can be used as is on all transverse application
but need to be slightly modified when used on longitudinal
engines.  Material needs to be trimmed from the flanges to
accommodate the internal ribs in this block.  Relieve the front
seal in two areas and the rear seal in one area (Figure 2).  For
proper fit the seal should lay flat on the cylinder block.

For additional information see AERA Technical Publications: ES 19


                                     The AERA Technical Committee


April 1991 - TB 758

##END##
 OIL PUMP DRIVE/DISTRIBUTOR GEAR
  Effect Of Oil Thickening On Oil Pump Drive/Distributor Spiral
               Gear On Cadillac And Other Engines

It has been reported that oil thickening, caused by overheating,
can cause failure of the oil pump drive and distributor gears in
Cadillac and possibly other engines.  On Cadillac, the
distributor gear set is lubricated by oil spray from the timing
chain.

Thickened oil reduces this lubricating spray and also imposes an
added load on the oil pump.  Replacing the failed parts is only a
temporary remedy.  To completely correct this situation, it is
necessary to disassemble the engine and clean it thoroughly.


                                     The AERA Technical Committee


September 1972 - SPB 9

##END##
 ENGINE INSTALLATION CAUTION
                 Engine Installation Caution on
         1981 GM 6.0L (368 CID) 4-6-8 Equipped Vehicles


AERA members should exercise special caution when installing 1981
GM 6.0L (368 CID) 4-6-8, or modulated displacement engines into
Cadillac manufactured vehicles.

The 4-6-8 engine was designed by Cadillac to turn off 2 or 4
cylinders at a time during reduced load conditions to increase
fuel economy.  Reducing the number of active cylinders is
accomplished through valve selector solenoids to control whether
a valve will open or remain closed.  While the piston still
travels up and down in the cylinder, both intake and exhaust
valves remain closed when the cylinder is deactivated.  

Frequent owner complaints finally lead most dealerships to
disconnect those parts of the system that controlled cylinder
deactivation, permitting the engine to operate on 8 cylinders all
of the time.  

AERA members have reported installing engines into these vehicles
and reconnecting all of the electrical connectors found in the
engine compartment.  This has led to erratic engine operation
caused by attaching sensors that specifically dealt with the
modulated displacement option.  It is therefore extremely
important to tag all electrical connections, even those that are
not attached to a sensor or other component.


                                     The AERA Technical Committee


November 1989 - SB 173


##END##
 HYDRAULIC LIFTER UPDATE
                           Hydraulic Lifter Update On
                        GM 4.1L (252 CID) HT-4100 Engines


A revised hydraulic lifter assembly has been released by General
Motors for the 4.1L (252 CID) HT-4100 engine used exclusively in
Cadillac automobiles.

The revised lifter assembly carries part #5234360 and features a
revised foot radius for improved service life.  It replaces
lifter #5234235 for this engine only.  The former lifter should
be used for the current 6.0L (368 CID) engine and all past model
V-8 gasoline engines used after 1968.  Whenever lifter
replacement is called for on 4.1L (252 CID) engines, the new part
number should be substituted.

Aftermarket manufacturers have followed suit and offer the
revised component under the following part numbers.

              Dana                        213-1685
              Pioneer Barnes              VT-969
              Sealed Power                HT-969
              TRW                         VL-73

Check with your aftermarket parts warehouse or distributor for
additional part numbers.

The illustrations below feature a representative aftermarket design of
the lifter.  However, the ribs are simply used for identification and
may appear in different locations depending on manufacturer.


                                                                    
                                          The AERA Technical Committee


December 1990 - TB 721
Please Destroy TB 334

##END##
 LOW COOLANT OR LOSS ON 1997-2001 GM 3.0L EGNINES
                                                  Low Coolant Or Loss On 
                                         1997-2001 GM 3.0L VIN R Engines

AERA Members have reported a low coolant or coolant loss on 1997-2001 GM 3.0L VIN R engines. This engine was used in the Cadillac Catera. 

Customers may complain of low coolant light being on and or engine overheating as well. An oil cooler cover leaking due to an adhesion condition between the oil cooler cover and the engine block may cause this condition. 

Remove the oil cooler cover from the engine and the old sealant from the engine block and the oil cooler cover. Use only a plastic or metal scraper to remove the old sealant residue. Clean both surfaces using a solvent that will not leave any residue on those surfaces. 

Apply a .080 bead of sealant, Part #2378521 (Canada use Part @#88901148) or equivalent, in the groove around the engine oil cooler cover as shown in Figure 1. Install the engine oil cooler cover back to the engine block and torque to 22 ft/lbs.

                                                                          The AERA Technical Committee
 CRANKSHAFT MAIN BEARING UPDATE ON HT-4100 ENGINES
                Crankshaft Main Bearing Update On
                GM 4.1L (252 CID) HT-4100 Engines


Cadillac has updated the design of the main bearings for all 4.1L
(252 CID) HT-4100 engines.

The new bearings feature a slightly bigger wall thickness.  The
#5 main bearing has been reduced in length from 1.029 to .982. 
This was done to reduce the amount of oil at the rear seal by
providing a channel to direct oil away from the rear seal. 
Several aftermarket bearing manufacturers have updated their
inventory to reflect the new Cadillac specifications.

The main bearing oil clearance can only be checked on these
engines with the cylinder heads and intake manifold installed and
torqued to specifications.  Bearing oil clearances can differ
greatly between an unassembled and assembled engine.  Overall oil
bearing clearance should never exceed .002.

(ITALICS ON) 
For additional information see AERA Bulletins: TB 474R, TB 491 &
TB 702
(ITALICS OFF)

                                     The AERA Technical Committee


October 1990 - TB 703

##END##
 LOWER END KNOCKING NOISE ON HT-4100 ENGINES
                                      Lower End Knocking Noises On
                                   GM 4.1L (252 CID) HT-4100 Engines

Some Cadillac automobiles equipped with 4.1L (252 CID) HT-4100 engines
may experience lower end knocking noises.

According to Cadillac, such a noise may be caused by interference between the cylinder block or piston and the first crankshaft counterweight (see illustration).  Apparently later style crankshafts were produced with fully machined counterweights to eliminate interference conditions.

Transverse engines use crankshaft Part #1629092 while longitudinal
engines use crankshaft Part #1629093.

For additional information see AERA Bulletins: TB 474R & TB 491

                                                                            The AERA Technical Committee
 LOOSE INTAKE MANIFOLD BOLTS ON HT4100 ENGINES
                                   Loose Intake Manifold Bolts On
                              1982-83 Cadillac 4.1L (252 CID) V-8 HT4100 Engines

Oil consumption, excessive coolant loss and poor performance may be due to loose intake manifold bolts on some 1982-83 Cadillacs equipped with subject engines.

To cure the problem, carefully retorque the bolts.  This is preferable to installing a new gasket because the new gasket will crush over time and lead to another loss of bolt torque.

If the intake manifold gaskets must be replaced, not that a restrictor in the center exhaust crossflow port is located on 1983 right bank gaskets.  This restrictor is not required on 1982 engines.

When retorquing the bolts, the correct sequence and ft-lbs must be adhered to or engine distortion may occur.  The sequence is shown below:

                    Bolt Tightening Sequence

1.  Tighten bolts 1,2,3 & 4 in sequence to 15 ft-lbs (20.0 N·m).
2.  Tighten bolts 5 thru 16 in sequence to 22 ft-lbs (30.0 N·m).
3.  Retighten all bolts in sequence to 22 ft-lbs (30.0 N·m).
4.  Repeat Step 3.

                                                                    The AERA Technical Committee
 CLICKING NOISE
                                                   Clicking Noise On
                                               GM 4.5 & 4.9L Engines

AERA members should be aware of a noise coming from the front of 4.5 & 4.9L Cadillac engines.  The clicking or rasping noise may appear on new and remanufactured engines.

Improper clamping load of the bolts that attach the water pump pulley to the water pump has been found to be the cause. Excessive paint buildup in the threaded bolt holes of the water pump flange may prevent the bolts from achieving the proper torque.  A single loose bolt may allow the pulley to wobble
slightly, resulting in the clicking noise.  

Technicians should be instructed to remove the paint by running a tap down the threaded bolt holes of the pulley flange before mounting the water pump to the engine.  Both original equipment and replacement water pumps may be affected by this condition.

                                                                         The AERA Technical Committee