| CYLINDER HEAD BOLT CAUTION |
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 |
| CRANKSHAFT CAUTION FOR 3.2L ISUZU ENGINES |
Crankshaft Caution For
1996-2002 Isuzu 3.2L Engines
The AERA Technical Committee offers the following crankshaft caution for 1996-2002 Isuzu 3.2L engines. This caution is expressed to engine rebuilders when crankshaft replacement is required. This engine series has used two different crankshaft assemblies during the above mentioned time period. Intermixing those crankshafts may produce a no-start situation.
The difference in the crankshafts is in the diameter of the ignition reluctor wheel attached to between the 3rd and 4th rod journal. The measurement difference is only slight and may not be noticed if only visual comparison of the two crankshafts is made.
To determine which crankshaft you?re working on it is suggested to measure outside diameter of the reluctor wheel on the crankshaft and refer to the chart below.
Application Engine Model Reluctor Diameter OE Crank Part #
1996-97 ? 6VD1 6.937 (176.200 MM) 8971094432
1997 ? -2002 6VD1W 7.250 (184.150 MM) 8791318572
The difference, however, is enough to interrupt the ignition signal from the crankshaft to allow a no start condition. Changing the crankshaft out to is one method of correction and removing the old reluctor wheel and placing it on the replacement crankshaft is another.
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| HYDRAULIC LIFTER REPLACEMENT ON 3.2L SOHC ENG. |
Hydraulic Lifter Replacement On
1992-96 Isuzu 3.2L SOHC Engines
The AERA Technical Committee offers the following information regarding hydraulic lifter replacement on 1992-96 Isuzu 3.2L SOHC engines. This information applies to new, rebuilt or lifters that have been disassembled and cleaned.
To assure proper operation of this lifter, it should be primed with engine oil before it is installed into the rocker arm. Doing so will eliminate the possibility of the lifter being dislodged before the lifter is fully primed with pressurized engine oil.
To prime this lifter submerge it in clean engine oil, then gently compress and decompress the lifter until no air bubbles come out while doing so. The rocker arm should then be dipped in oil and the lifter inserted into the rocker arm. Assemble all lifter/rockers and then reassemble those components to their rocker shaft. This procedure will also prevent trapped air in the rocker arm socket, even though the lifter is self-bleeding.
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| REAR CRANKSHAFT OIL SEAL LEAK |
Rear Crankshaft Oil Seal Leak On
1992-1994 4BD2TC GM Diesel Engines
The AERA Technical Committee offers the following information for rear crankshaft oil seal leaks on 1992-94 4BD2TC GM diesel engines*. This four cylinder turbocharged diesel engine is used in GMC and Chevrolet W4 model trucks. If this leaking condition can be verified as coming from the rear main seal, installing a revised oil seal may resolve the leak.
The installed position of this seal, Part #97072823, is critical to assure an effective seal. When correctly installed, the seal depth should be .445-.468 (11.3-11.98 mm) below the rear face or the crankshaft. The use of tool number J41269 (Figure 2) is also advised to minimize seal distortion during installation.
Trucks that are equiped with an automatic transmission require the removal of the pilot bushing before installing a new seal. After installing the new seal, install the flywheel/flexplate and torque the mounting bolts to 115 ft. lbs.
* This engine is built for GM by Isuzu Motors.
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| PISTON PROTRUSION |
Piston Protrusion On
1985-97 Isuzu 4BD1/T & 4BD2-TC Diesel Engines
The AERA Technical Committee offers the following information on piston protrusion for 1985-97 Isuzu 4BD1/T & 4BD2-TC diesel engines. The following information has not been previously published in Isuzu service manuals. The information listed below has been obtained from engines during disassembly and verified by Isuzu engine builders.
Engine Desired Piston Protrusion
4BD1 .020-.034 (.508-.864 mm)
4BD1-T .020-.034 (.508-.864 mm)
4BD2-TC .020-.037 (.508-.940 mm)
These engines have been observed to suffer from cylinder block/head deck erosion that is observed during disassembly, most often because of a head gasket failure. If erosion is noted, the head and block surfaces require resurfacing before they can be placed back in service.
Engines assembled with piston protrusion higher than the listed specifications may produce excessive cylinder pressure or allow piston to valve contact. Excessive cylinder pressure may lead to engine or head gasket failure.
AERA members are adjusting the center to center distance of this engine?s connecting rod. In some instances, the standard size factory bushing Part #ES1-12251-027 can be used. In other situations where a more dramatic correction is required, a bushing that has a .020 smaller inside diameter is used.
AERA is currently aware of one aftermarkert supplier for the .020 smaller ID bushing with Part #S4653L. One AERA member has also reported occasional connecting rod bolt breakage if the bolts are not replaced during engine assembly.
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| CAM TIMING CHAIN MARK |
Cam Timing Chain Marks On
1976-88 Isuzu 1.8 & 1.9L Engines
AERA members have expressed some confusion aligning cam timing marks on 1976-88 Isuzu 1.8 & 1.9L engines. The confusion starts while reading service manual information referencing marked plates on the cam timing chain. Apparently, some aftermarket timing chains do not have the marked plates which indicate the correct positioning for installation. The original equipment chain has two marked plates that must align with sprocket marks when properly installed.
The installation of an unmarked timing chain can be achieved by ensuring the correct number of links are between the cam and crankshaft sprocket marks. To correctly position the sprocket marks also depends on which direction you are counting, clockwise or counter clockwise.
When properly timed, the number of plates between the sprocket marks will be 24 counting in a clockwise direction. The number of plates counting counter clockwise should be 21, when the chain is properly installed. Both timing methods are viewed from the front of the engine.
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| CRANKSHAFT SPECIFICATIONS |
Crankshaft Specifications On
1985-89 Isuzu 2.0L VIN F Engines
The AERA Technical Committee offers the following crankshaft specifications for 1985-89 Isuzu 2.0L VIN F engines. It appears that depending upon the
source, different crankshaft journal diameters have been published. The amount of difference is slight, but could cause an engine failure if the incorrect
specifications are used to grind the crankshaft.
The correct diameter for the connecting rod journal is 1.9262-1.9268 (48.925-48.940 mm). The correct diameter for the main bearing journal is 2.2016-
2.2022 (55.921-55.936 mm).
Crankshaft Specifications Oil Clearance
Connecting Rod Journal 1.9262-1.9268 .0007-.0020
(48.925-48.940 mm)
Main Bearing Journal 2.2016-2.2022 .0008-.0020
(57.980-58.00 mm)
Stroke 3.2283 (82.00 mm)
End Play .002-.010 (.051-.254 mm)
Previously published information indicated the main journal diameter could be as much as .0016 larger than the above specifications. Whereas, the rod
journal may have been as much as .0014 (.0356 mm) larger. If an engine is assembled with either of these situations, there may be insufficient bearing
oil clearance.
The AERA Technical Committee |
| CRACKED HEAD ON 83-87 1.7, 2.2, 2.5 & 2.8L ENGINE |
Cracked Cylinder Heads On
1983-87 Isuzu 1.7, 2.2, 2.5 & 2.8L Diesel Engines
AERA members have reported cracked cylinder heads on 1983-87 Isuzu 1.7, 2.2, 2.5 & 2.8L diesel engines. The specific location of these cracks has been between the valve seats. In some instances these cracks have not leaked while
performing a pressure testing operation. Those cracks, however, may eventually leak coolant into the combustion chamber if they are not repaired during cylinder head reconditioning procedures.
At least two methods of repair have been used to seal these cracks which include welding or installing a sleeve type repair. This bulletin will cover procedures to repair using the sleeve type repair. Close examination of the exhaust manifold mounting surface will reveal a drilled coolant passage running between each intake and exhaust seat. Those passages are sealed at the exterior end with cup type freeze plugs.
The repair involves removing the freeze plug(s) and using a reamer to enlarge the passage for proper fit of a sleeve (valve guide liner). AERA is currently aware of at least one aftermarket supplier of a kit intended for this type of
repair. The kit includes everything required to successfully repair at least 16 cracked locations.
After the hole has been enlarged to the proper size, remove chips and other debris from the passage. Then, apply enough Loctite(R) 620 sleeve retaining compound to the inside walls of the passage. The applied coating should have a wet look the entire length of the passage. Installing the intended sleeve (valve guide liner) with the split toward the valve spring side of the cylinder head can now be done with the appropriate driver.
The procedure can be completed by installing a new cup plug in each location to seal the passage. Some AERA members report easier access by tapping the hole and installing a pipe plug. The cylinder head should then be pressure tested before completing the rest of machine work required.
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| OVERHEATING PROBLEMS |
Engine Overheating Problems On
1989 Isuzu 2.6L Engines
AERA machine shops have reported engine overheating problems on 1989 Isuzu 2.6L engines used in Troopers and Pick Ups. Though the cooling system was filled during engine installation, the overheated engines have a low coolant level when inspected. Before disassembling the engine, consider that the cooling system may not have been properly filled during installation.
Isuzu recommends the following fill procedure:
1) Make sure that the thermostat jiggle valve is positioned at the top of the
thermostat housing (Figure 1).
2) Remove the thermal valve from the thermostat housing. Remove the radiator
cap and set the temperature control lever to the highest heat position.
3) Fill the cooling system until coolant flows from the thermal valve opening.
4) Apply a thread locking compound to the thermal valve and install it into the
thermostat housing. Finger tighten the valve using the metal housing. Rotate
the valve one additional revolution and align it as show in Figure 2 below.
5) Start the engine and let it reach normal operating temperature. Check the
coolant level in the radiator and refill as necessary. If no air bubbles are
present in the filler neck, install the radiator cap.
The AERA Technical Committee |
