Engine - Important Effects of Modifications
REF. NO. 01/29ATO: OUR MERCEDES-BENZ PASSENGER CAR DEALERS
DATE: July 1994 (Supercedes S.I. 01/29 January 1994)
Revision: Additional engine applications
SUBJECT:
A. ENGINE 119.97
ENGINE BLOCK IN OPEN-DECK DESIGN
B. ENGINE 104, 120
MODIFIED CAMSHAFT BEARING CAP
A. ENGINE 119.97
ENGINE BLOCK IN OPEN-DECK DESIGN
As of April 1993, an open-deck engine block was phased into production in engine 119.975 (model 124.034) and in engine 119.971 (models 140.042/043).
The open-deck engine block was also phased into production in engine 119.974 (model 124.036), in engine 119.972 (model 129.067) and in engine 119.970 (models 140.051/070) in January 1994.
Effective Serial Number
As of April 1993, the casting number for the open-deck engine block for engines 119.971 975 is 119 011 22 01, the previous casting number was 119 011 19 01 for the closed-deck engine block. As of January 1994, the casting number for the open deck engine block for engines 119.970 972 974 is 119 011 2401. the previous casting number was 119 011 23 01 for the closed-deck engine block.
The open-deck design allows the cylinders to be "free-standing" in the engine block (Figure 1) as compared to the closed-deck design (Figure 2).
NOTE!
Listed below are important differences in the open-deck engine block as compared to the closed-deck engine block.
^ Distributor ignition (DI) control module
Due to the different layout of the knock control, be sure to use the DI control module specified for the engine block being installed. The modules differ for the open - and closed-deck designs. (See Parts Microfiche, 1329 for Model 124, 0536 for Model 129 and 1185 for Model 140.)
^ Cylinder head gasket
The cylinder head gasket is 3 mm wider in the fire ring area, for the open-deck engine block.
^ Cylinder head
Engines 119.970/974/972:
The cylinder head installed on either version engine block, as of engine end numbers:
119.970 2 021 287
119.974 2 004 782
119.972 2......... (as of production phase-in can be retrofitted to a closed - or open-deck engine block.
Engines 119.975/971:
NOTE:
The oil passage in the cylinder head for the open-deck engine block has been relocated. The previous version cylinder head which was installed on the closed-deck engine block cannot be installed on the open-deck engine block. The cylinder head installed on the open-deck engine block can be retrofitted to a closed-deck engine block (see Parts Microfiche, 1119).
^ Engine block thread holes (for cylinder head bolts)
The thread holes in the open-deck engine block (for the cylinder head bolts) are tapped and threaded directly into the block. This eliminates the use of Heli-Coil inserts. In a repair situation, Heli-Coil inserts can be used.
^ Cylinder head bolts
The new head bolts are nickel plated (previously phosphate-coated).
The head bolt washers are phosphate-coated (previously nickel-plated).
Cylinder head bolt torque specifications remain the same.
Cylinder head bolt length in positions 1, 3 and 5 have been increased to 218 mm (Figure 3).
CAUTION!
Individual parts from the open-deck and the closed-deck engine blocks are not interchangeable. The PDC's will continue to stock parts for the closed-deck engine block.
NOTE:
The nickel alloy head bolts and phosphate-coated head bolt washers from the open-deck engine block can be retrofitted to the closed-deck block.
B. ENGINE 104,120: MODIFIED CAMSHAFT BEARING CAP
As of January 1993, a modified camshaft bearing cap was phased into production. This modified version eliminates the use of dowel pins for the purpose of centering the bearing cap. The bearing cap is now centered by the bearing cap bolt (as in engine 111). As the bolt is torqued to proper specifications the bearing cap centers itself. (See SMS, Job no. 05-2200, for proper torquing procedure.)