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Isuzu  Engine Information

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The following technical bulletins were published by AERA.


                                         Engine Prelubrication Procedure for
                                                 Isuzu Diesel Engines

Isuzu Truck of America has released the following procedure for prelubricating diesel engines.  This procedure applies to new, remanufactured or partially disassembled engines.

If the engine is equipped with a turbocharger be sure to pour 4 oz. of clean SAE CD grade engine oil into the turbo charger oil passage.  This can best be accomplished by removing the oil supply line to the turbocharger.  Rotate the compressor or turbine wheel by hand to distribute the oil.  Attach any oil supply lines that have been removed.

While holding the fuel shutoff lever closed crank the engine with the starter for 10 seconds.  This is applicable to all engines, whether turbocharged or naturally aspirated.  Pause for one minute to permit the batteries to recover and the starter to cool down and repeat this process two more times.

Release the fuel shutoff lever and start the engine.  Follow break-in procedures as outlined in the appropriate service manual or AERA's Break-In Procedure.

                                                                      The AERA Technical Committee


                                               Valve Train Ticking Sound On
                                                  1992-98 Isuzu 3.2L Engines

The AERA Technical Committee offers the following information regarding a valve train ticking sound on 1992-98 Isuzu 3.2L engines. 

One or more hydraulic lash adjusters do not fully extend due to varnish build up inside the adjusters. This condition results from exceeding the oil and filter change intervals on the vehicle. 

There are a couple of ways to possibly cure this problem that Isuzu offers. One of the simplest ways is changing the engine oil and filter using a 0W-30 synthetic engine oil prior to replacing any engine components. If the noise persists after those changes, refer to the following information. 

Once we have determined which bank the noise is coming from, the cylinder head valve cover needs be removed so that we can inspect each rocker arm for clearance at the valve tip. The noisy rocker arms are the ones with clearance when the rocker is on base circle of the cam and the valve is closed as shown in Figure 1. 

Note: Each cylinder head has an oil pressure relief valve that controls oil pressure to the rocker arms. If all rocker arms have clearance and/or the rocker arm pivot shaft is worn, then the cylinder head oil pressure relief valve may be stuck in the open position. 

Remove the rocker arm(s) that have clearance on them and inspect the wear pattern of the hydraulic lash adjuster surface contact with the valve stem as shown in Figure 2. Then remove the hydraulic lash adjuster from the rocker arms using your fingers. Do not damage the O-ring on the outside of the lash adjuster or replacement of the entire rocker arm is required. 

Insert a paper clip into the hole at the top of the lash adjuster and depress the spring loaded check ball while completely pushing in the piston at the opposite end. Some traces of oil may come out of the check ball hole. 

Carefully remove the O-ring and spray the lash adjuster piston with cleaner to remove any varnish while holding the piston open. Submerge in cleaning solvent with the check ball depressed and pump the piston repeatedly to allow the solvent to penetrate through the lash adjuster. 

Submerge the adjuster in clean 0W-30 synthetic engine oil with the check ball depressed and pump the piston repeatedly to allow the engine oil to penetrate through the lash adjuster. Then allow the piston to extend fully to fill the adjuster. 

Reinstall the O-ring and lube the rocker arm bore that houses the adjuster with 0W-30 synthetic engine oil, then push the adjuster back into place. Inspect for leaks at the check ball and piston by attempting to compress the adjuster without depressing the check ball. 

                                                                          The AERA Technical Committee


                                       Main Bearing Torque Caution For
                                   1992-98 Isuzu 3.2L VIN V & W Engines

The AERA Technical Committee offers the following caution on main bearing torque used for 1992-98 Isuzu 3.2L VIN V & W engines. This information should be referenced anytime main bearing caps are being installed and is used for both SOHC and DOHC engines.

During disassembly, make sure the main caps are marked as to their position front to rear. If they are not, number them before removing them in proper sequence shown in Figure 1 below. The bolts should be removed while the block is room temperature.

When installing the main caps, ensure reference mark on the cap points towards the front of the engine and the cap being installed is at the proper location. Tighten the main cap bolts to specifications and sequence shown below in Figure 2.

Tighten main cap bolts # 17,18,19,20,21,22,23 and 24 to 29 ft/lbs.
Tighten main cap side bolts # 1,2,3,4,5,6,7 and 8 to 29 ft/lbs.
Tighten main cap and Oil Gallery bolts # 9,10,11,12,13,14,15 and 16 to 22 ft/lbs. 
Then, tighten bolts # 9,10,11,12,13,14,15 an additional 55-65° degrees of rotation.

                                                                            The AERA Technical Committee


                                                 Valve Bridge Stud Caution For
                                   1998-2003 Isuzu 7.8L 6HK1-TC Diesel Engines

The AERA Technical Committee offers the following information regarding a caution for bridge studs on 1998-2003 Isuzu 7.8L 6HK1-TC diesel engines. It has been reported valve bridge studs have moved during engine operation and cylinder head service work.

Damage will result to either the rocker arm or valve rocker bridge if the stud installed height is higher than 1.496" (38.000 mm).  The correct installed bridge stud height is listed as 1.457-1.496" (37.000-38.000 mm). These studs are pressed into the cylinder head casting and use of special tool # J43268 will locate the studs to the correct height. 

This engine built by Isuzu is used in the following vehicle models sold by Isuzu, Chevrolet Trucks and GMC Trucks.

1999-2003 Chevrolet & GMC F-Model (T-Series) Medium Duty Tilt Cab Models.
2000-2003 Chevrolet & GMC WT 5500 Medium Duty Tilt Cab Models.
2003 Chevrolet & GMC C6500-C8500 Series Models (Some Topkick & Kodiak).
1998-2002 Isuzu FSR/FTR/FVR Commercial Vehicles.
2000-2003 Isuzu, Some FRR Commercial Vehicles.

                                                                        The AERA Technical Committee


                                                Excessive Smoking On
                           Isuzu C223 (2.2L) Turbocharged Diesel Engines

The AERA Technical Committee has been informed of an excessive smoking situation on the Isuzu C223 turbocharged diesel engine. This engine is often used in Trooper II and P'up (pickup) vehicles.

The C223 turbo-diesel engine has a PCV system that is complicated enough to be classified as intimidating.  The crankcase ventilation system uses two devices not normally found in gasoline engine applications.  

The first device, is an oil separator/retention tank, which acts as nothing more than a drop filter.  Crankcase fumes travel through a mesh medium that allows much of the oil to collect and drop out of the air stream into the bottom of the tank. Collected oil will drain back into the oil pan.  The remaining oil fumes are drawn through the induction system and become part of the combustion mixture.  

The second device is part of the return line drain from the retention tank.  This return line uses a one way check valve, Part # 8-94145-952-0. that allows oil to return to the oil pan, but does not expose the lower crankcase to the vacuum of the PCV system.  If this check valve becomes clogged or stuck closed, oil
may accumulate in the retention tank.  Excessive amounts of oil will then enter the induction system past the retention tank, resulting in dramatic engine smoking.  Smoke is particularly heavy during morning engine startup.

                                                                       The AERA Technical Committee


                                      Cylinder Head Bolt Caution On
                                                Isuzu 2.6L Engines

A loose head bolt has been found to be the cause of coolant leaks on some Isuzu 2.6L engines.  The leakage occurs at the center head bolt on the exhaust manifold side of the engine and seems to be caused by high engine temperatures.  This heat may cause the head bolt to stretch and lose its clamping ability, allowing coolant to seep past the head gasket and into the combustion chamber.  If the loosened bolt is not replaced, there is a possibility th at coolant deposits will accumulate on the exhaust valve's seating ace.

Correction of this situation requires removal of the cylinder head and complete inspection of the exhaust valves for deposits.  Install a new head gasket and replace all head bolts.  See the illustration below and torque bolts in sequence to 58-72 ft. lbs.  All components must be torqued to specification prior to
adjusting the valve train.  The engine may be rotated by the using a 17 mm wrench/socket on the power steering pulley nut.  Cold valve adjustment specification for both intake and exhaust is .008.
                                                                               The AERA Technical Committee


         Cylinder Head Installation Isuzu 4BD1/T Diesel Engines

Isuzu Truck of America recommends the following procedure when installing the cylinder head on 4BD1/T diesel engines.

Position the cylinder head gasket on the cylinder block with the TOP mark facing up and the FRONT mark facing forward. Lubricate the head bolts with engine oil on 4BD1 engines and tighten in two steps using the sequence outlined in the illustration below.  Turbo charged 4BD1T engine head bolts should be lubricated with molybdenum disulfied grease before installation.

There are two different length head bolts used.  Be sure to install the shorter length bolts on the injection pump side of the engine.

Engine            Bolt Status      Step 1         Step 2

4BD1              Reused         47-54 lbs.ft.  80-87 lbs.ft.
                       New               47-54 lbs.ft.  69-76 lbs.ft.

4BD1T             N/A               50 lbs.ft.       65 lbs.ft. *

                  * Then turn each bolt an additional 90o-120o.  

For additional information see AERA Bulletin: TB 628

                                                                              The AERA Technical Committee


                   Revised Cylinder Head Removal & Installation Procedure For
                                   2001-2003 GM 6.6L VIN 1 Diesel Engines

The AERA Technical Committee offers the following information on a revised cylinder head installation procedure for 2001-2003 GM 6.6L VIN 1 diesel engines. These modern diesel engines are referred to as the Duramax diesel and are a result of a joint venture between GM and Isuzu. This procedure should be used any time the cylinder head is being removed and re-installed. This supersedes information found in earlier published service manuals.
Figure 1. Head Bolt Removal Sequence  

It is now recommended that all M12 cylinder head bolts should be replaced at the time of cylinder head installation. These bolts have a pre-applied molybdenum disulfide coating for thread lubrication. Do not remove the coating or use any additional lubricant. Improperly lubricated threads will adversely affect the bolt torque and clamp load. Improper bolt torque and clamp load can lead to engine damage.

Notice: The left and right cylinder head gaskets are not interchangeable. Improper placement of the cylinder head gasket will block coolant and oil passages. Blocked coolant and oil passages will cause severe engine damage. Three different grade (thickness) head gaskets are available and use is determined by piston projection (See Figure 1). Those gaskets are also marked by no hole, one hole or two holes to indicate the different grades as well as ?L" and ?R" for left and right banks respectfully.

Cylinder Head Gasket Selection

                          Right Side         Left Side	       Piston Protrusion                  Holes 
Grade A             97288223         97309562       .0088 to less than .0108       none
Grade B             97288224         97309563       .0108 to less than .0128       one
Grade C             97309561         97288228       .0128 to less than .0148         two

After selecting the proper gasket determined by the cylinder with the highest piston protrusion follow the steps listed below to tighten the new cylinder head bolts.

1. Tighten new 12 mm bolts in sequence to 37 ft/lbs (50 Nm).
2. Tighten new 12 mm bolts in sequence to 59 ft/lbs (80 Nm). 
3. Rotate those bolts in sequence an additional 90° turn using a torque angle meter.
4. Rotate those bolts in sequence an additional 75° turn using a torque angle meter.
5. Tighten the M8 cylinder heat bolts to 18 lb ft (25 Nm).

AERA is unaware of an aftermarket supplier for these gaskets or bolts.

                                                                            The AERA Technical Committee

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