| The following technical bulletins were published by AERA. |
| | SALVAGED OEM ENGINE PARTS | Salvaged O.E.M. Engine Part Caution
More new engine components are being salvaged O.E.M. than ever before. O.E.M. production lines can save a block by custom fitting, for example, an oversize rod or main bearing. By doing so, an otherwise rejected part will be restored.
It does present a problem, however, when the engine is to be rebuilt. The unsuspecting rebuilder or mechanic will discover too late, that standard parts will not work. The unfortunate thing is that the engine has to be disassembled to find the problem and additional time spent in securing the special part.
To illustrate more specifically - the following situations have een brought to our attention:
1. Integral valve guides having oversize ID with valve stems oversize to match.
2. One or more replaceable valve guides with oversize OD.
3. All main bearing bores oversize and bearings with thick walls to compensate.
4. One or more valve lifter (tappet) bores oversize. Body of tappet is oversize to
match.
5. One or more rod and main bearings undersize ID to fit undersize crankshaft
journals.
6. Cylinder bores honed slightly oversize and fitted with special high limit
service pistons.
7. Push rods of varied lengths. (Must be identified and returned to their original
position).
8. A small quantity of cylinder blocks with deck height .030 lower than specified.
A special thicker head gasket was employed to compensate.
Summary: The best preventative action is to make no assumption that parts are going to be standard. The exceptions are small in number, but they do exist and must be considered. At times the blocks will be identified when special parts are used, but the mark of a good technician is still that he makes a thorough dimensional check and knows that the parts he installs match those originally used.
The AERA Technical Committee | | FLYWHEEL RESURFACING CAUTION | Flywheel Resurfacing Caution
The AERA Technical Committee offers the following information regarding flywheel-resurfacing caution.
The clutch surface of the flywheel is a key bridge between the power generation source and the power transmission system. Problems that accompany the
flywheel into the shop fall into four major categories: Excessive wear, hard spots and metal discoloration, warping and runout. Below is a brief description of the four major categories.
1. Excessive Wear. Caused by grooves cut into the flywheel by a worn clutch
disc.
2. Hard Spots and Metal Discoloration. Caused by the slippage of the clutch
disc. The wasted energy transformed into heat causes nucleation and creation
of carbide hard spots in the flywheel surface. The heat caused by slippage
is localized in areas of the flywheel. Due to the mass of the flywheel acting as
a heat sink, localized heat of friction is drawn off rapidly which cools the hot
spots quickly and causes the to harden.
3. Warping. Caused by abnormal heating and cooling that a flywheel encounters.
This is accentuated by the fact that most of today's flywheels are made of
forged steel vs. cast iron. This forged steel, though more durable I subject to
greater warping due to its metallurgical makeup. A regular flat flywheel that
looks perfect may have .005-.010 dish.
4. Runout. May be caused by previously misaligned resurfacing methods. This
misalignment is most likely caused when the flywheel is resurfaced without
referencing the crankshaft flange.
SAE specification J618B notes that maximum runout for a flywheel surface is .0005 per inch of flywheel diameter. For instance if we had a flywheel with a
diameter of 13, take the 13 X .0005 = .0065 surface runout. Experience has shown that runout greater than .002 will most likely cause chatter and unbalance vibration. Excessive runout greater than .005 may cause severe vibration and self-destruction.
Flywheel grinders are used for resurfacing both flat and stepped (or recessed) flywheels. The flywheel machine achieves required flatness with minimum
amounts of material removed. Abrasive grinding processes will eliminate hard spots efficiently, creating a smooth and homogeneous surface. Alignment
or parallelism of the flywheel surface is maintained by referencing the crankshaft-mounting surface for the work piece. Critical centering of recessed flywheels is accomplished by using custom adapters or centering cones.
When confronted with resurfacing stepped or recessed flywheels, not only does the surfaces have to be parallel and correctly centered, but also the depth
relationship between steps must be maintained. Simply put, if .020 is removed from the lower step area, then .020 must be removed from the upper step area.
To assure that the correct dimension is to be used, measuring the clutch surface depth before and after grinding is done is recommended. Since grinding stones leave a radius on the corner of the clutch cover-mounting surface, squaring the radius to a perpendicular edge should finish the job. This will insure that the mating clutch pressure plate assembly will match up squarely when reinstalled.
The AERA Technical Committee | | CRANKSHAFT SEAL LEAKS | Rear Main Crankshaft Seal Leak On
Audi 2.0L, 2.2L, 2.3L Engines
AERA member shops have reported rear main oil seal leaks on the 2.0L, 2.2L, and 2.3L engines. The engines are used in the Audi 80/90 and 100/200 cars.
To verify that the engine oil leak is coming from the rear main seal, and not from the engine's valve cover, use florescent dye in the engine oil and a black light.
Audi has released an improved crankshaft seal, part number 068-103-051G to help correct this problem. The new seal went into production after VIN # 44 LN026115 for the 100/200 models, and after VIN # 8A LA048000 for the 80/90 models.
Audi also advises using locking compound on the flywheel bolts to seal the crankcase. The torque for the non-shoulder bolt is 55 lbs. ft. The torque for the shouldered bolt is 74 lbs. ft. and Audi advises to always use new shouldered bolts.
The AERA Technical Committee | | HYDRAULIC VALVE LIFTER NOISE | Hydraulic Valve Lifter Noise On
1988-91 Audi 2.0, 2.2 & 2.3L Engines
The AERA Technical Committee has been informed of hydraulic valve lifter noise on 1988-91 Audi 2.0, 2.2 & 2.3L engines. This noise may be heard both at engine start-up and during low engine RPM. To reduce the possibility of undesirable lifter noise, Audi now supplies a new lifter, Part #034109309AD for all 4 & 5 cylinder engines.
It is important to note that it may take as long as a week to purge all air from this new lifter after installation. At the time of this publication, AERA is unaware of an aftermarket supplier of this lifter.
The AERA Technical Committee | | OVERSIZE CAM BEARING HOUSING BORES ON VARIOUS ENG. | Oversize Cam Bearing Housing Bores on Various Engines
AERA members have reported finding oversize cam bearing housing bores on several engines during the past months. At times it is a single bore that is oversize, other times there are several oversize cam bearing housing bores in the same cylinder block.
AERA cautions members to pay particular attention to this area of the cylinder block during disassembly. It is recommended to measure each cam bearing housing bore or the outside diameter of each cam bearing as is it removed as part of the estimate process. This will prevent surprises on the assembly bench after the cylinder block has been machined to completion.
In most cases, these oversize cam bearings are not available from any source on an off-the-shelf basis. Custom fitting a standard bearing in an oversize bore can be accomplished by knurling or by plating metal onto the outside diameter of the bearing.
AERA recommends making your customer aware of the fact that his/her engine was manufactured with an oversize/nonstandard housing bore and the various procedures that can be used to overcome this problem. Some of these solutions may not be approved by OE, but have been proven to be successful in the field.
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 | | | | | 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 | | NEW CYLINDER LINER O-RINGS | New Cylinder Liner O-Ring Seals On
Cummins NH/NT 6 Cylinder Engines
Cummins Engine Company has released new O-ring seals for the cylinder liners in NH/NT 6 cylinder engines. The new seals are made of an EP material and have a smaller diameter cross-section.
The new seal replaces both the old center seal #3008998 and the old lower seal #183049. The new seal carries Cummins part #3032874 and is black in color with one blue dot.
The new O-ring seals are not to be intermixed with the former seals on the same liner. Cylinder liner deformation will result. You can use the former seals and new seals in the same engine as long as they are used in the correct combinations on each liner. The illustration below shows the correct combinations.
The AERA Technical Committee |
|
|
