| OIL LEAKS AT OIL FILTER ADAPTOR |
Oil Leaks At Oil Filter Adapter On
1989-91 GM 4.3L (262 CID) Engines
General Motors 4.3L (262 CID) engines installed in 1989-91Chevrolet S-10 and GMC S-15 trucks may experience oil leaks at theoil filter adapter.
Engines in these applications use a remote oil filter assembly that requires an oil filter adapter to be installed at the oil filter mounting area of the cylinder block (see illustration). The original gasket fails to seal properly and may also cause the adapter bolts to lose torque. Simply retorquing the bolts may stop the leak, but will not result in a permanent repair. Replacement of the gasket and adapter is recommended. The revised gasket carries GM Part #10172754 and the adapter GM Part #10172750.
Position the gasket on the adapter and hold it in place with petroleum jelly. Do not use any type of sealer on the gasket or the adaptor. Each of the remote filter lines is fitted with an O- ring. Be sure to torque the two mounting bolts to 13-18 lbs.ft. and the remote line bolts to 22-29 lbs.ft.
The AERA Technical Committee |
| 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.
The AERA Technical Committee |
| MOUNTING BRACKET BOLT BREAKAGE ON 7.0 & 7.4L ENGINES |
Mounting Bracket Bolt Breakage On
1996-2000 GM 7.0 & 7.4L VIN M, P, B & D Engines
AERA members have reported repeated generator mounting bracket bolt breakage on 1996-2000 GM 7.0 & 7.4L VIN M, P, B & D engines. These engines are used in Chevrolet and GMC C6 and C7 conventional medium duty trucks. The frequency of breakage has not been consistent between customers, but may be related to multiple engine duty cycles.
To correct this condition, GM now offers a new generator rear support bracket and brace rod assembly. Refer to the list below to obtain components required to install the new assembly.
Part Number Description Quantity
11505992 Nut 1
15766728 Bracket, Rear Generator, 7.0L 1
15766727 Bracket, Rear Generator, 7.4L 1
15764193 Assembly, Brace Rod 1
15650963 Washer 1
09424338 Bolt 1
Before installing the brace and bracket, apply a small amount of medium strength threadlocker (Part #12345382 or aftermarket equivalent) to the bolt/nut threads. Then, torque the mounting bolt and stud nut to 37 ft/lbs (50 Nm).
The AERA Technical Committee |
| CYLINDER LINER COMPRESSION RING GASKETS |
Detroit Diesel Allison 71 Series
Cylinder Liner Compression Ring Gaskets
GMC has changed their specifications for the 71 series diesel engine cylinder liner compression ring gaskets. Their tolerance specifications are such that when replacing these gaskets they must be replaced in matched sets.
The compression ring gaskets are color-coded on the top surface with a 3/4 black, white or orange stripe. Each color represents the following compressed thicknesses:
Black stripe .059 - .063
Orange stripe .058 - .062
White stripe .057 - .061
Mixing the colors of rings under any one cylinder may cause engine damage.
The AERA Technical Committee |
| SURFACING CYLINDER HEAD CAUTION |
Cylinder Head Resurfacing Caution On
GM (GMC) 5.7L (350 CID) Diesel Engines
General Motor Corporation warned that it is not to possible to resurface the cylinder head on the 5.7L (350 CID) diesel engine due to the extremely tight clearance between the valves and the head of the piston. The prechamber must be recessed into the cylinder head by more than .005 or must not protrude out of the head by more than .003.
Note: GMC states that a cylinder head must be replaced if it is warped more than .010.
Before the cylinder head is reinstalled, make sure that the mounting bolt holes are tapped deep enough in the block and threads are not damaged. Blow out any chips or liquid and lightly oil the bolt threads in the block. Screw the bolt into the block by hand to a depth that is less than the cylinder head thickness.
Bolts that are rusty should be cleaned by wire brushing the threads. Before installing, lubricate the threads and underneath the head of the engine bolt with engine oil. Torque to 130 ft.lbs. (176Nm) in the sequence shown below:
The AERA Technical Committee |
| CYL HEAD GASKET SELECTION ON 94-96 2.2L VIN 4 |
Cylinder Head Gasket Selection On
1994-96 GM 2.2L VIN 4 Engines
The AERA Technical Committee offers the following information on head gasket selection for 1994-96 2.2L VIN 4 engines. Beginning in 1994, this engine was installed in Chevrolet & GMC S series trucks. Those vehicles are rear wheel drive applications (RWD). Previously this engine was only offered in front wheel drive vehicles (FWD). The head gasket for the different applications is specific to that application.
When this engine is installed in a FWD application, larger water passage holes are required in the head gasket. Those holes are illustrated below by arrows pointing to the specific locations. The gasket on the right side does not have the large front openings and is intended for use in RWD engines.
If the head gasket is installed for the wrong application, coolant flow will be affected and possible engine damage may result.
The AERA Technical Committee |
| VALVE CROSSHEAD CLEARANCE |
Valve Crosshead To Rocker Lever Clearance On
NH, NT & V-1710 Series Cummins Engines
Valve crosshead nose to rocker lever clearance on the subject engines must be checked during engine rebuild and at any time valve crossheads are replaced on engines using crossheads No. 123416 & 3000326. A minimum of .020 (.51 mm) clearance must be present as illustrated in Fig. 1, on the cylinder being checked with valves completely closed and crosshead in the upmost position. After installing rocker lever assemblies, check crosshead to rocker lever clearance as follows:
1. Turn crankshaft slowly in direction of rotation until the valves are closed on the cylinder being checked. With rocker lever held firmly against the stellite pad of the crosshead, a .020 (.51 mm) wire type feeler gauge must pass between the crosshead nose and the lower beam section of the rocker lever.
2. If the feeler gauge does not pass through:
a. Remove the rocker lever and/or crosshead and grind the nose of the crosshead or rocker lever beam in the area circled in Fig. 1 until enough clearance is obtained.
b. If the rocker is ground, grinding should cover the complete area illustrated in Fig. 2 in a continuous arc. Do NOT grind just the contact area.
Caution: A sharp depression in this area will cause a stress riser and eventual failure of the lever. Grind only enough material to achieve the required clearance. If grinding enters the oil passage, the rocker lever must be junked.
c. Grind sharp edges smooth.
The AERA Technical Committee |
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| CRANKSHAFTS INDUSTRIAL |
Crankshafts Used In Industrial Applications On
GM (Chevrolet) 5.7L (350 CID) Engines
When the GM (Chevrolet) 5.7L (350 CID) industrial engine is used in some applications such as lift trucks, the only crankshaft that is applicable has the forging number 1182. Dimension A of the rear flange is slightly smaller than that of other crankshafts used in General Motors 5.7L (350 CID) engines.
The larger flange crankshafts will not pass through the center hole of the bell housing. This is very critical when an oil clutch system is used.
The AERA Technical Committee |
| BURNED EXHAUST VALVES |
Burned Exhaust Valves, Low Power & Hard Starting On
Cummins NH & NT Engines With Jacobs Brake 25B & 30
Cummins Engine Co. reported that if the following complaints are experienced in the NH and NT engines equipped with Jacobs brakes, the slave piston clearance should be checked:
A. Exhaust valve burning
B. Low engine power when at operating temperature
C. Engine hard to start or will not start at operating temperature
A standard slave piston adjustment of .018 +/- .001 has been established. The .018 clearance setting is a cold setting which results in zero slave piston to crosshead clearance when the engine is at operating temperature.
Should the slave piston clearance setting be less than .018, the following conditions outlined in A, B or C above may result as well as affect breaking power.
If the slave piston clearance is greater than .018 +/- .001, the following problems may occur:
1. Engine injector train component problems
2. Injector carboning
3. Bent injector push rods
4. Worn injector adjusting screws
5. Decreased camshaft life
6. Cam follower and follower shaft failure
7. Delay in breaking action
If the above problems are experienced and the engine is equipped with a Jacobs brake, the slave piston clearance should be checked with the latest Cummins specifications.
The AERA Technical Committee |
