| The following technical bulletins were published by AERA. |
| | ENGINE FAILURE | Engine Failure On 1978-89 Mercedes Benz 3.0L Diesel Engines
The AERA Technical Committee offers the following information regarding engine failure on 1978-89 Mercedes Benz 3.0L diesel engines. This failure has been reported on vehicles with high mileage or shortly after a partial engine repair.
The damage reported has ranged from lack of compression to catastrophic component failures. The cause of these failures has been related to a lack of tension on the engine?s timing chain, allowing piston to valve contact. The reason for insufficient tension on the timing chain is a broken chain tensioner spring. See Figure 1 below to view one such spring that broke shortly after the cylinder head and tensioner were re-installed. The spring fatigued and broke after the outside diameter of the coil wire had worn excessively.
The timing chain tensioner requires removal and re-installation anytime the cylinder head is removed. It is therefore advised to replace this spring, Part # A1109933901 anytime the tensioner is removed.
The AERA Technical Committee | | CONNECTING ROD BOLT TORQUE CAUTION | Connecting Rod Bolt Torque Caution For
Allis Chalmers 201, 301 & 426 Cubic Inch Engines
The AERA Technical Committee offers the following information on connecting rod bolt torque specifications for Allis-Chalmers engines. This information applies to both early and late style engines, as several different hardware combinations have been used. Previously published TB-2018 should be discarded as TB-2018R contains updated information.
Two different connecting rod and cap mating surface finishes were used and identification can be made by visual inspection. Early style connecting rods have a serrated mating surface between the cap and the rod. Middle and Late style connecting rods can be identified by smooth/machined surfaces between the cap and the rod.
ALL MODELS
When installing, use a light amount of engine oil on capscrew threads and on the underside of the capscrew head at the mating surface. Tighten hardware using a minimum of two incremental torque steps, three on higher torque hardware (7.0L). Non-serrated connecting rod caps MUST be aligned with the rod during installation. To do so, install hardware finger tight, use two feeler gauges between the rod/cap assembly and the side of journal to hold assembly snug to one side of journal. Tighten hardware in multiple steps and then remove feeler gauges.
Allis-Chalmers engine models: 2000 series, 3.3 and 4.9-liter series (2200, 2800, 2900, 433 & 649 types, etc.)
Early style rods use hex-head capscrew with washer. The rod cap bolt holes have a 30° degree chamfer. Capscrew size used is .375" ? 24 x 2.00" long, grade 8, tighten those capscrews to 50 ft/lbs.
Later style rods have the rod cap chamfer deleted and a new 12-point capscrew introduced. Capscrew size used is .375 - 24 x 2.00 long, grade 100, tighten those capscrews to 45 ft/lbs.
Note: Do not use later 12-point capscrews in early rods with chamfered holes or loosening of capscrews will occur. Early rods may be machined and balanced to accept later capscrews.
Allis-Chalmers engine models: 3000 Series, 7.0 liter series (3400, 3500, 3700, 3750 & 670 types, etc.)
Early style rods use serrated rod caps with hexhead capscrews and washers. Capscrew size .437 20 x 2.25 grade 8, tighten those capscrews to 85 ft/lbs.
Middle style rods use smooth machined rod and cap mating surfaces. Socket head capscrew size .437 20 x 2.156 long, grade 100, tighten those capscrews to 70 ft/lbs.
Later style rods use smooth machined rod and cap mating surfaces. 12-point capscrew size .437 20 x 2.156 long, grade 100, tighten those capscrews to 70 ft/lbs.
Note: Do not use middle or later type hardware in early-serrated connecting rods.
The AERA Technical Committee | | CRANK COUNTERWEIGHT BALANCE WEIGHT REMOVAL & INSTALL | Crankshaft Counterweight Balance Weight Removal & Installation on
Mercedes 280 (110 Series) Engines
Removing the front balance plate from Mercedes Benz 110 engine
series crankshafts can be quite difficult, especially since the
balance plate is riveted to the crankshaft.
AERA members have developed a procedure that is safe and cost
effective:
1) With a 3/8 end mill, remove the head of each of the four
rivets that attach the plate to the counterweight.
2) Simultaneously drive all four rivets out of the crankshaft
to prevent distortion of the plate.
3) Refinish the crankshaft as required.
4) Install the plate by pressing 4 new rivets, Mercedes Benz
Part No. 000661 006013 through the counterweight and into the
plate.
5) Hold the plate to the crankshaft counterweight by wedging a
5/8 or 3/4 bolt, cut to length, between the second
counterweight and the plate. Position the cap screw end of each
bolt right underneath the plate countersink. This will mushroom
the end of the rivet, securing the plate.
The AERA Technical Committee
September 1990 - TB 692
##END## | | CHILLED IRON CAMSHAFT ON 2.6L M103 ENGINES | Chilled Iron Camshaft On
1987-91 Mercedes Benz 2.6L M103 Engines
The AERA Technical Committee offers the following
information on a chilled cast iron camshaft for 1987-
91 Mercedes Benz 2.6L M103 engines. Beginning in March
of 1989, these engines received a chilled cast iron
camshaft and rocker arms with carbide inserts. This
change was done as a product improvement and
intermixing previous and revised components is not
recommended.
To identify engines with the revised components, the
manufacturer has stamped an S into the exhaust side
of the cylinder head as shown below. Updating previous
cylinder heads with the revised components is advised,
and those heads should also be stamped to reflect the
revised components. Below is a list of parts required
to incorporate this change.
Component Part Number
Camshaft 1030506401 (Code #53)
Rocker Arm 1030501033
Ignition Dist.
Rotor Bracket 1031580840
Optional 1031580740
Torx Head Screw 1039900122
Camshaft Gear 1030520601
Cam Gear Mounting Bolts 1039900022
AERA is currently unaware of an aftermarket source for
these components and they are available only from the
manufacturer.
The AERA Technical Committee
February 1998 - TB 1545
##END## | | MEASURING INSTALLED VALVE STEM HEIGHT | Measuring Installed Valve Stem Height For
1992-95 Mercedes Benz 3.2L DOHC Engines
The AERA Technical Committee offers the following information on measuring installed valve stem height for 1992-95 Mercedes Benz 3.2L DOHC engines. The method of measuring the installed stem height for this engine is not made in the conventional manner. According to Mercedes Benz, the prescribed method to measure is from the tip of each valve to the camshaft-bearing base (camshaft housing bore).
To correctly measure the intake and exhaust installed valve stem heights; lay a 6mm diameter bar onto the base of the camshaft bearing bores. Measure the distance at dimension ?T" as shown in Figure 1 below, using a caliper and record for all locations. Refer to chart below for specifications for the intake and exhaust installed valve stem height.
Location Standard ?T" Dimension Repair Limit ?T" Dimension
Intake .953-.974" (24.21-24.75mm) .943-.965" (23.96-24.51mm)
Exhaust .874-.896" (22.21-22.75mm) .865-.886" (21.96-22.51mm)
If, during checking the specifications against the recorded values and any measurement are under repair size, you must install new valve seats and/or valves in the head. These new seats and/or valves will help to properly position the hydraulic lash compensators for their correct operation.
Caution: Do not use a magnetic tool to remove the bucket type cam followers. If a magnetic tool is used and the buckets retain even a small amount of magnetism, the buckets may attract metal particles within the oil supply. Which, may cause possible camshaft lobe and follower failure.
Note: Dimension (H) shows a reference for a new head height of 5.350-5.354 (135.89-135.992 mm). The minimum head height is 5.335 (135.509 mm).
The AREA Technical Committee | | CYLINDER HEAD DIFFERENCES ON OM352/A ENGINES | Cylinder Head Differences On
Mercedes Benz OM352/OM352A Engines
Mercedes has made significant changes to the cylinder head, cylinder head gasket and bolts on OM352/OM352A engines.
Cylinder head:
Starting with engine end number 712 988, the cylinder head casting was strengthened. This later-style cylinder head may be installed on earlier engines as long as the appropriate head gasket is selected.
Cylinder head gasket:
Prior to engine end number 708 085, the cylinder head gasket featured small, round water transfer holes. As of engine end number 708 085, the head gasket was modified and now features much larger, oval water transfer holes. The later style cylinder head gasket should be used with the strengthened cylinder head.
According to Mercedes Benz as well as aftermarket gasket manufacturers, the later style head gasket (large water transfer holes) may be used with the earlier cylinder head as well.
Cylinder head bolts:
Up to engine end number 678 154, Mercedes used studs and nuts to mount the cylinder head to the block, all later engines use cap screws (bolts). Studs should be lubricated on the threads and torqued to 82 lbs.ft. Mount the cylinder
head and torque the nuts in sequence (see illustrations) to 44 lbs.ft, then 66 lbs.ft. The final torque is reached at 82 lbs.ft.
Cylinder head cap screws should be lubricated on the threads and underneath the bolt head before installation. The torque sequence and torque values are the same for cap screws as they are for the nuts.
The AERA Technical Committee | | CYLINDER HEAD SPECS FOR 240D MERCEDES ENGINES | Cylinder Head Specifications on
Mercedes Benz 240D Engines
AERA members are cautioned to observe the following
specifications when remanufacturing Mercedes Benz 240D engine
#OM616-912 or OM616-916 cylinder heads.
The cylinder head height is measured from the cylinder head cover
rail to the deck surface. New cylinder heads measure 3.327 -
3.346 (84.5 - 85 mm) with a recommended minimum reuse thickness
of 3.307 (84 mm).
Both intake and exhaust valves should be recessed .002 - .060
(.05 - 1.5 mm) below the cylinder head deck surface.
The AERA Technical Committee
October 1989 - TB 594
##END## | | CLY. BLOCK SPECIFICATIONS ON MERCEDES 240D ENGINES | Cylinder Block Specifications on
Mercedes Benz 240D Engines
AERA members are cautioned to observe the following specifications when remanufacturing Mercedes Benz 240D engine #OM616-912 or OM616-916 cylinder blocks.
The cylinder block deck height is measured from the center line of the crankshaft main bearing bore to the deck of the block and should be 9.547 - 9.563 (242.5 - 242.9mm).
The cylinder block has a bore size of 91mm and uses dry sleeves in each cylinder bore which should be installed flush with the deck surface of the block. Piston-to-wall clearance is .0008 -.0012 measured near the bottom of the piston.
The main bearing housing bore diameters are 2.9331 - 2.9338 (74.50 - 74.52mm) with the main bearing cap bolts torqued to 58 -65 ft.lbs.
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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