Mercedes Benz Diesel Engines OM636 and OM621 | Manual cover

Mercedes-Benz Workshop Manual OM Diesel Engines 636-621

$25.00

Workshop manual for Mercedes-Benz OM636 and OM621 diesel engines, inline 4-cylinder, 1.8, 1.9 and 2.0 liters

Factory technical manual for Mercedes-Benz OM636 and OM621 engines, used as a service reference for diagnostic, maintenance, disassembly, assembly and repair operations. Includes workshop procedures, technical data, tightening torques, cylinder head, engine block, timing, injection system, intake manifolds, electrical equipment, lubrication and cooling.

PDF in English | 627 pages | Instant download.

Original workshop manual for OM636 and OM621 engines
Includes factory tables, diagrams and specifications
Covers engine disassembly, inspection, adjustment and repair
Ideal for maintenance, restoration and tuning work

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Mercedes-Benz Workshop Manual OM Diesel Engines 636-621 | PDF

Workshop manual for Mercedes-Benz OM636 and OM621 diesel engines, inline 4-cylinder, 1.8, 1.9 and 2.0 liters.

The Mercedes-Benz OM636 and OM621 engines represent a very important stage in the development of the brand’s diesel engines and were used in passenger cars and working vehicles throughout the 1950s and 1960s. Thanks to their mechanical robustness, relatively simple design and broad presence in classic models, they remain highly relevant for maintenance, restoration and repair work.

This digital PDF edition was originally conceived as a workshop service manual and includes factory technical information for the OM636 and OM621 engines, together with references to the differences between their various versions. The content covers diagnostic, inspection, disassembly, measurement, adjustment, assembly, repair and parts replacement procedures, with information on the cylinder head, engine block, crankshaft assembly, timing, injection system, air and fuel filter, intake and exhaust manifolds, engine electrical equipment, lubrication and cooling.

To review the scope of the content and included operations in greater detail, also check the Complete index tab.

Main topics covered in the Mercedes-Benz OM636 and OM621 engine manual

General data, technical specifications and adjustment values
Tightening torques, inspections and engine adjustment procedures
Cylinder head, engine block and timing gear housing
Crankshaft, rotating assembly and lower-end assembly
Timing, synchronization and adjustment checks
Diesel injection system and related procedures
Fuel filter, air filter and associated ducting
Intake and exhaust manifolds
Engine electrical equipment
Lubrication system and cooling system

Mercedes-Benz vehicles equipped with OM636 engine

W136 series: 170 D, 170 Da and 170 Db
W120 series: 180 D
Unimog: U 2010, U 401, U 402 and U 411

Mercedes-Benz vehicles equipped with OM621 engine

W121 series: 190 D and 190 Db
W110 series: 180 Dc, 190 Dc and 200 D
Light commercial vehicles: L 319 D and O 319 D
Unimog: U 421

Important: this is a general reference list of vehicles and applications that used versions of the OM636 and OM621 engines. In addition to passenger cars, utility vehicles and Unimog models, the OM636 family also had industrial and marine applications. Other applications within these engine families may require verification depending on year, market and configuration.

Article features:

Format: PDF
Language: English
Pages: 627
File size: 146.6 MB
Delivery method: Download link

Because of its technical approach and level of detail, this digital edition is especially useful for workshops, restorers, experienced mechanics and owners who need to consult specific procedures without relying on a complete printed copy.

Frequently asked questions about the Mercedes-Benz OM636 and OM621 engine manual

Which engines are included in this edition?

This edition brings together service information for Mercedes-Benz OM636 and OM621 engines, including references to differences between variants within both engine families.

Does it include adjustment data, tightening torques and inspection procedures?

Yes. The manual covers general data, tightening torques, inspection procedures, adjustment operations and service procedures for a wide range of workshop tasks.

Does it include content on injection, timing and cooling?

Yes. It includes sections dedicated to the diesel injection system, timing, lubrication and cooling, along with other mechanical and electrical engine groups.

Is it only useful for passenger cars?

Not exclusively. Although it is especially useful for classic Mercedes-Benz sedans, it can also serve as a technical reference for utility applications equipped with OM636 or OM621 engines, provided the exact configuration is verified.

Does it include differences between OM636 and OM621 engine variants?

Yes. The manual covers different versions within both engine families and incorporates tables showing differences between variants, which is especially useful when checking components, adjustments and specific applications.

Is this PDF only useful for full restorations?

No. In addition to major repairs, it is also useful for maintenance, inspections, adjustments, diagnostics and partial work on classic Mercedes-Benz engines.

Mercedes-Benz OM636 and OM621 Engine Manual | Index

This index lists the main sections and job numbers included in the Mercedes-Benz Workshop Manual OM Diesel Engines 636-621.

Each entry is listed in accordance with the manual's original technical layout and numbering.

0 General

0-1 Technical Data for Engine OM 636
0-2 Technical Data for Engine OM 621
0-3 Running-in and/or Break-in Instructions for New or Overhauled Engines
0-4 Lubricants
0-5 Fuels and Additives
0-6 Cooling System
0-7 Measures for Winter Operation
0-8 Preservation of Engines Taken out of Operation and/or Placed in Storage
0-9 Lubrication and Maintenance

00 Tightening Torques, Testing and Adjusting Work on the Engine, as well as Disassembly and Assembly of Engine

00-0 Technical Data, Measures and Adjusting Values
00-1 Tightening Torques
00-3 Adjusting Valve Clearance
00-4 Checking Injection Nozzles and Glow Plugs
00-5 Testing Compression Pressure
00-6 Checking and Adjusting Feed Begin
00-7 Checking Adjustment of Camshaft to Crankshaft
00-8 Testing Timing
00-9 Measuring Suction and Discharge Action of the Fuel Feed Pump and Checking the By-Pass Valve
00-10 Bleeding Fuel System
00-11 Adjusting Idling Speed
00-12 Adjusting No-Load Maximum Speed
00-13 Adjusting Cable Control between Glow Starter Switch and Injection Pump
00-20 Disassembly and Assembly of Engine (Individual Removal of Assemblies and Parts)

01 Cylinder Head, Cylinder Crankcase, Timing Gear Housing Cover, Operation Hour Counter and Revolution Counter - Drive

01-0 Technical Data, Measures and Adjusting Values
01-1 Removal and Installation of Pre-combustion Chamber
01-3 Removal and Installation of Cylinder Head
01-5 Milling and Pressure-Testing of Cylinder Head
01-6 Checking and Replacing Valve Guides
01-7 Inserting or Replacing Valve Seat Ring
01-8 Machining of Valve Seats in Cylinder Head
01-11 Removal and Installation of Operating Time Indicator and Subsequent Installation of Same, OM 636
01-12 Removal and Installation of Revolution Counter Drive
01-15 Removal and Installation of Timing Housing Cover, OM 636
01-16 Checking and Subsequent Machining of Timing Housing Cover, OM 636
01-21 Removal and Installation of Oil Pan
01-25 Disassembly and Assembly of Cylinder Crankcase, OM 621
01-26 Cleaning and Pressure-Testing of Crankcase and Surface-Grinding of Same, if Necessary
01-27 Boring and Honing of Cylinder Bores
01-29 Installing Cylinder Liners, OM 636

03 Crank Assembly

03-0 Technical Data, Measures and Adjusting Values
03-1 Removal and Installation of the Pulley on the Crankshaft
03-2 Removal and Installation of Pulley and Counterweight on Crankshaft, OM 621
03-3 Removal and Installation of Front Seal Ring for the Crankshaft, OM 621
03-5 Removal and Installation of Crankshaft with Flywheel
03-6 Grinding of Crankshaft
03-7 Balancing Crankshaft
03-8 Re-balancing New Flywheel, OM 621
03-9 Re-bedding of Crankshaft
03-11 Removal and Installation of Pistons with Connecting Rods
03-13 Repairing and Re-bushing of Connecting Rods
03-15 Fitting Pistons and Rings into Cylinders
03-16 Removal and Installation of Flywheel
03-17 Removal and Installation of Annular Grooved Bearing and Locking Ring in Crankshaft
03-18 Replacing Ring Gear of Flywheel
03-19 Grinding Clutch Surface of Flywheel

05 Timing

05-0 Technical Data, Measures and Adjusting Values
05-1 Removal and Installation of Rocker Arm Brackets with Rocker Arms and Push Rods, OM 636
05-2 Disassembly, Checking, Repairing and Assembly of Rocker Mounting, OM 636
05-3 Checking Push Rods, OM 636
05-5 Removal and Installation of Rocker Arm Brackets with Rocker Arms, OM 621
05-6 Disassembly, Checking, Repairing and Assembly of Rocker Mounting, OM 621
05-8 Removal and Installation of Valve Tappets, OM 636
05-9 Checking Valve Tappets, OM 636
05-11 Removal and Installation of Valves
05-13 Grinding Valves
05-14 Testing Valve Springs
05-16 Replacing Valve Stem Seal
05-20 Chain Elongation and Chain Noises, OM 621
05-21 Removal and Installation of Chain Tightener, OM 621
05-22 Checking of Chain Tightener, OM 621
05-23 Removal and Installation of Idler Sprocket and Idler Sprocket Support, OM 621
05-24 Repairing of Idler Sprocket and Idler Sprocket Support, OM 621
05-25 Removal and Installation of Guide Sprocket, OM 621
05-26 Repairing of Guide Sprocket, OM 621
05-27 Removal and Installation of Double Roller Chain, OM 621
05-28 Removal and Installation of Drive (Intermediate Gear Shaft) for Injection Pump and Oil Pump, OM 621
05-29 Removal and Installation of Guide Rails in Cylinder Head, OM 621
05-31 Removal and Installation of Timing Gears, OM 636
05-35 Removal and Installation of Camshaft and Bearings, OM 636
05-36 Camshaft and Bearing, OM 621
05-38 Grinding of Camshaft
05-39 Re-bedding of Camshaft

07 Injection System

07-0 Technical Data, Measures, Adjusting Values and List of all Diaphragms and Control Springs, as well as Dimensions of the Control Springs which are Installed in the Different Governor Types of the Injection Pumps, OM 636 and OM 621
07-1 Test Sheets with Test Data and List of Test Sheets for Injection Pumps and Governors
07-2 List of Injection Pumps with Governor and Feed Pump Installed up to Date
07-3 Fuel Injection System
07-4 Design and Operation of the Fuel Injection System
07-5 Testing and Adjusting Injection Pump
07-8 Checking and Adjusting Operations on Installed Injection Pump
07-9 Checking and Adjusting Mechanical Additional Control, OM 621
07-10 Replace Sealing between Pipe Connection and Pressure Valve Holder
07-11 Removal and Installation of the Injection Pump
07-13 Removal and Installation of Fuel Feed Pump
07-14 Checking and Partial Repairing of Fuel Feed Pump
07-15 Removal and Installation of Injection Lines, Vacuum Line, and Fuel Hoses
07-16 Checking, Cleaning and Fabricating of Pressure Lines or Injection Lines
07-17 Removal and Installation of Nozzle Holder with Injection Nozzle
07-18 Disassembly, Cleaning and Assembly of Nozzle Holder and/or Injection Nozzles and Adjusting Opening Pressure
07-21 Throttle Duct
07-23 Checking and Repairing of Throttle Duct
07-25 Removal and Installation of Injection Timing Device
07-27 Subsequent Installation of Injection Timing Device and Removal and Installation of Pump Drive Shaft Bearings, OM 636
07-28 Disassembly, Checking and Assembly of Injection Timing Device

09 Fuel Filter and Air Filter

09-1 Removal and Installation of Fuel Main Filter
09-3 Cleaning and Testing of Fuel Main Filter and Checking the By-Pass Valve
09-5 Cleaning of the Fuel Pre-filter
09-8 Air Filter

14 Intake Manifold and Exhaust Manifold

14-1 Removal and Installation of Intake Line with Throttle Duct
14-3 Intake Lines
14-5 Removal and Installation of Exhaust Manifold
14-8 Exhaust Manifold

15 Electrical Equipment of Engine

15-0 Technical Data, Measures, Testing and Adjusting Values
15-1 Removal and Installation of Starter
15-2 Removal and Installation of Solenoid Switch
15-3 Maintenance Hints for Integral Starter
15-4 Disassembly and Assembly of Starter
15-5 Electrical Testing of Starter
15-6 Trouble Shooting Hints for the Starter
15-11 Removal and Installation of Generator with Generator Support and Generator Holder
15-12 Maintenance Hints for the Generator
15-13 Disassembly and Assembly of Generator
15-16 Electrical Testing of Generator and Regulator Cutout
15-17 Trouble Shooting Hints for the Generator
15-30 Glow Plug
15-31 Removal and Installation of Glow Plug
15-32 Testing of Glow Plugs
15-33 Glow Starter and Stop Switch
15-40 Battery

18 Engine Lubrication

18-0 Technical Data, Measures and Adjusting Values
18-1 Engine Lubrication
18-3 Removal and Installation of Oil Relief Valve in Main Oilway
18-5 Cleaning and Testing of Oil Relief Valve
18-7 Removal and Installation of Oil Filter
18-9 Disassembly, Cleaning and Assembly of Oil Filter
18-11 Removal and Installation of Oil Pump
18-14 Repairing of Oil Pump
18-16 Removal and Installation of Drive Shaft with Helical Gear for Driving Oil Pump, OM 621

20 Engine Cooling

20-0 Technical Data, Measures and Adjusting Values
20-1 Engine Cooling
20-3 Forced Circulation Cooling with Heat Exchanger and Centrifugal Pump for Built-in Engine, OM 636
20-5 Removal and Installation of the Water Pump
20-6 Replacing V-belt, Checking and Adjusting Tension
20-7 Removal and Installation of Water Pump Pulley
20-8 Repairing Water Pump
20-12 Fan
20-15 Fan Bearing Bracket with Belt Pulley and Support of Fan Bearing Bracket, OM 636

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