Mercedes-Benz W123 Diesel Owners Repair Guide

This guide was deigned to help owners of W123 Diesels. It will help those who own Mercedes-Benz 240D, 300CD, 300D, 300SD, 300TD or any vehicle with a OM615, OM616 and OM617 Engine. Lack of maintenance is the most common reason for a catastrophic failure on old and high mileage vehicles.

 

Info About the W123:

The Mercedes-Benz W123 is a range of cars produced by German manufacturer Mercedes-Benz from November 1975 to January 1986. The W123 models surpassed their predecessor, selling 2.7 million units before the production ended in the autumn 1985 for saloon/sedan and January 1986 for coupé and estate/station wagon.

Like its predecessors, W123 gained the reputation of being over-engineered, well-built, durable, and reliable. Many taxi companies chose W123 for this reason, and they were common sight in Germany. Reaching 500,000 or 1,000,000 km with minor mechanical issues. Once the W123 reached the end of service life, they were often shipped to Africa and third world countries where they were highly esteemed for ability to travel on rough roads and further without frequent maintenance.

 

Model Designation Info:

Model designation corresponded to the engine displacement, chassis type (coupé or estate/station wagon), fuel type (for diesel engines only), and availability of fuel injection system (for petrol engines only):

  • C for Coupé
  • T for Tourismus und Transport (estate/station wagon)

No designation was given for the long-wheelbase: it was simply called "Lang" (long) in the brochures and order forms.

  • D for Diesel
  • E for Einspritzung (fuel injection)

When the diesel engine is turbocharged, TURBODIESEL is affixed to the right side of the boot lid.

As for the chassis codes, W123 is the saloon/sedan, S123 the estate/station wagon, C123 the coupé, V123 the long-wheelbase saloon/sedan a.k.a. Lang, and F123 refers to the bare long-wheelbase chassis as used for ambulances and other conversions.

 

Engine Info:

The world's first turbocharged diesel engine for passenger vehicle, OM617 A was finally introduced in W123 models in September 1979, exclusive to 300 TD TURBODIESEL for European market. The same engine is offered in the North America and Japan in 1981 as 300D TURBODIESEL, 300CD TURBODIESEL, and 300TD TURBODIESEL. 

The OM616 was a 2.4 L (2,404 cc) engine with power output of 48 kW (64 hp). In August 1978 the pre-combustion chamber was updated for more swirl and more efficient combustion. The new camshaft pushes the valves deeper so the air and exhaust gases have less resistance. The engine capacity was lowered to 2.4 L (2,399 cc) to satisfy engine displacement tax laws in Europe, but power output rose to 54 kW (72 hp). A similar technique power update around these time was also done on the OM615 and OM617

  • OM616.912 53 kW (71 hp)
    • 1976-1978 W123 (240D)
  • OM616.916 48 kW (64 hp)
    • 1973-1976 W115 (240D)
    • 1976-1985 W123 (240D)
  • OM616.936 53 kW (71 hp)

OM617.912

This was introduced with the W123 series. Power originally was 80 PS (59 kW; 79 hp) @ 4000 rpm, torque 172 N⋅m (127 lb⋅ft) @ 2400 rpm. From September 1979 - 88 PS (65 kW; 87 hp) @ 4400 rpm, torque 172 N⋅m (127 lb⋅ft) @ 2400 rpm.

Applications:

OM617.952

The .952 is identical to the .951 apart from minor changes to fit the North American 123 chassis. It was also fitted to the European market W123 wagon, the 300TD. This was the only turbocharged OM617 fitted to a European W123. Power originally was 121 PS (89 kW; 119 hp) @ 4350 rpm, torque 230 N⋅m (170 lb⋅ft) @ 2400 rpm. From October 1982 - 125 PS (92 kW; 123 hp) @ 4350 rpm, torque 250 N⋅m (184 lb⋅ft) @ 2400 rpm. Vehicles sold to the North American market had EGR equipment fitted.

Applications:

 

Maintenance and Inspections:

  1. Inspect or replace the air filter
  2. Oil Change
  3. Inspect or replace Belts
  4. Diesel Purge to clean out the fuel system. After the purge change the Fuel Filters. There are 3 Filters. Primary(Large Spin On) Secondary(Inline Filter) Tank Screen(Strainer Type) The tank screen can be cleaned but if its too dirty it must be replaced. Inspect for any fuel leaks while the car is running. The rubber fuel injector return lines are common to leak.
  5. Valve Adjustment!!! It is very important to do a valve adjustment. Its recommended to be done every 12-15K miles or 1 year. If you dont know when it was done last just do it anyways. Here is a link to my guide on how to do a valve adjustment: https://lermscustoms.com/blogs/news/mercedes-benz-diesel-valve-adjustment-instructions
  6. Hard Starts or white smoke on start up is a sign the Glow Plugs or injectors need to be replaced. I recommend to use a reamer to clear the carbon from the chambers, this helps improve glow plug life. 
  7. Injectors! I recommend having your Injectors Rebuilt. You can also buy new ones.
  8. Flush the radiator with a process called Citrus Flush. Refill with MB Coolant or Zerex G-O5. Green Coolant is Harmful to the cooling system!
  9. Check or Adjust IP Timing
  10. Inspect Timing Chain Stretch
  11. Check The Lug Bolts
  12. Inspect or replace the Motor Mounts and Engine Shocks
  13. Vacuum Leaks can cause the car to not shut off, the door locks will not work, transmission shifting issues and more. Check all your vacuum lines are connected and the rubber connectors are not torn. 
  14. Clean or Delete the EGR System
  15. Check Or Replace Rear Diff Fluid, Transmission Fluid, Power Steering and Brake Fluid
  16. Check brake pads and inspect Control arm bushings and steering components for torn rubber boots. Grease if applicable. 
  17. Inspect the brushes on the Voltage Regulator it is recommended to inspect them every 50K. Replace when the brushes are near 5mm or Every 100k Miles.

 

 

Parts and Tools for Maintenance:

 

Mercedes-Benz W123 Diesel Engine Tune Up Kit w/ Valve Adjustment Wrenches

https://lermscustoms.com/collections/mercedes-benz-tools-and-parts/products/mercedes-benz-w123-om617-tune-up-kit-oil-change-fuel-filters-air-filter-seals

 

 

Valve Adjustment Wrench Kit

https://lermscustoms.com/collections/mercedes-benz-tools-and-parts/products/1961-1985-mercedes-benz-om-615-616-617-valve-adjustment-wrenches

EGR Delete Kit

https://lermscustoms.com/collections/mercedes-benz-tools-and-parts/products/om617-egr-delete

Diesel Purge Kit

https://lermscustoms.com/collections/mercedes-benz-tools-and-parts/products/mercedes-benz-om603-om616-om617-diesel-purge-kit

Lug Bolt Replacement

https://lermscustoms.com/collections/mercedes-benz-tools-and-parts/products/hrwheelboltset

Glow Plug Reamer

https://lermscustoms.com/collections/mercedes-benz-tools-and-parts/products/mercedes-benz-diesel-glow-plug-chamber-carbon-reamer-om616-om617

Magnetic Engine Oil Drain Plug

https://lermscustoms.com/collections/mercedes-benz-tools-and-parts/products/mercedes-benz-om616-om617-engine-oil-pan-magnetic-drain-plug

Fuel Tank Screen Removal Kit

https://lermscustoms.com/collections/mercedes-benz-tools-and-parts/products/w123-fuel-tank-strainer

Magnetic Rear Diff Plug

https://lermscustoms.com/collections/mercedes-benz-tools-and-parts/products/1966-1995-mercedes-benz-magnetic-rear-differential-oil-drain-plug

 

 

 

 

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Models North America and Japan

 

Years

Model

Engine

Power

Torque

W123  1977–1978 230 2.0 L M115 I4 93.0 hp (69 kW) @ 4800 125 lb-ft (169 Nm) @ 2500
   1977–1983 240D 2.4L OM616.912 I4 Diesel 62 hp (46 kW) @ 4000
from MY 1981 67 hp (50 kW) @ 4000
97 lb-ft (132 Nm) @ 2400
   1977–1981 280E 2.8 L M110 I6 142 hp (106 kW) @ 5750
from MY 1980: 140 hp (104 kW) @ 5500
149 lb-ft (202 Nm) @ 4600
from MY 1980: 145 lb-ft (197 Nm) @ 4600
   1978–1981 280CE 2.8 L M110 I6 142 hp (106 kW) @ 5750
from MY 1980: 140 hp (104 kW) @ 5500
149 lb-ft (202 Nm) @ 4600
from MY 1980: 145 lb-ft (197 Nm) @ 4600
   1977–1981 300D 3.0 L OM617.912 I5 Diesel 77 hp (57 kW) @ 4000
from MY 1981: 83 hp (62 kW) @ 4200
115 lb-ft (156 Nm) @ 2400
from MY 1981: 120 lb-ft (163 Nm) @ 2400
   1978–1981 300CD 3.0 L OM617.912 I5 Diesel 77 hp (57 kW) @ 4000
from MY 1981: 83 hp (62 kW) @ 4200
115 lb-ft (156 Nm) @ 2400
from MY 1981: 120 lb-ft (163 Nm) @ 2400
   1979–1980 300TD 3.0 L OM617.912 I5 Diesel 77 hp (57 kW) @ 4000 115 lb-ft (156 Nm) @ 2400
   1981–1985 300TD Turbo 3.0L OM617.952 I5 Diesel 125 hp (93 kW) @ 4350 181 lb-ft (245 Nm) @ 2400
   1981–1985 300D Turbo 3.0L OM617.952 I5 Diesel 125 hp (93 kW) @ 4350 181 lb-ft (245 Nm) @ 2400
   1981–1985 300CD Turbo 3.0L OM617.952 I5 Diesel 125 hp (93 kW) @ 4350 181 lb-ft (245 Nm) @ 2400
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Models (except North America and Japan)

Chassis code

Years

Model

Engine

Power

Torque

W123.020 1976–1981 200 2.0 L M115 I4 94 PS (69 kW; 93 hp) @ 4800 158 Nm (117 lb-ft) @ 3000
W123.220 1979–1985 200 2.0 L M102 I4 109 PS (80 kW; 108 hp) @ 5200 170 Nm (125 lb-ft) @ 3000
W123.280 1980–1985 200T 2.0 L M102 I4 109 PS (80 kW; 108 hp) @ 5200 170 Nm (125 lb-ft) @ 3000
W123.120 1976–1979 200D 2.0 L OM615 I4 Diesel 55 PS (40 kW; 54 hp) @ 4200 113 Nm (83 lb-ft) @ 2400
W123.120 1979–1985 200D 2.0 L OM615 I4 Diesel 60 PS (44 kW; 59 hp) @ 4400 113 Nm (83 lb-ft) @ 2400
W123.126 1976–1979 220D 2.2 L OM615 I4 Diesel 60 PS (44 kW; 59 hp) @ 4200 125 Nm (92 lb-ft) @ 2400
W123.023 1976–1981 230 2.3 L M115 I4 109 PS (80 kW; 108 hp) @ 4800 185 Nm (136 lb-ft) @ 3000
W123.223 1979–1985 230E 2.3 L M102 I4 136 PS (100 kW; 134 hp) @ 5100 201 Nm (148 lb-ft) @ 3500
W123.043 1977–1980 230C 2.3 L M115 I4 109 PS (80 kW; 108 hp) @ 4800 185 Nm (136 lb-ft) @ 3000
W123.243 1980–1985 230CE 2.3 L M102 I4 136 PS (100 kW; 134 hp) @ 5100 201 Nm (148 lb-ft) @ 3500
W123.083 1978–1980 230T 2.3 L M115 I4 109 PS (80 kW; 108 hp) @ 4800 185 Nm (136 lb-ft) @ 3000
W123.283 1980–1985 230TE 2.3 L M102 I4 136 PS (100 kW; 134 hp) @ 5100 201 Nm (148 lb-ft) @ 3500
W123.123 1976–1985 240D 2.4 L OM616 I4 Diesel 65 PS (48 kW; 64 hp) @ 4200
from 02/79 72 PS (53 kW; 71 hp) @ 4400
137 Nm (101 lb-ft) @ 2400
W123.125 1977–1985 240D LWB 2.4 L OM616 I4 Diesel 65 PS (48 kW; 64 hp) @ 4200
from 02/79 72 PS (53 kW; 71 hp) @ 4400
137 Nm (101 lb-ft) @ 2400
W123.183 1978–1986 240TD 2.4 L OM616 I4 Diesel 65 PS (48 kW; 64 hp) @ 4200
from 02/79 72 PS (53 kW; 71 hp) @ 4400
137 Nm (101 lb-ft) @ 2400
W123.026 1976–1985 250 2.5 L M123 I6 129 PS (95 kW; 127 hp) @ 5500
from 09/79 140 PS (100 kW; 140 hp) @ 5500
192 Nm (142 lb-ft) @ 3500
from 09/79 196 Nm (145 lb-ft) @ 3500
W123.028 1977–1985 250 LWB 2.5 L M123 I6 129 PS (95 kW; 127 hp) @ 5500
from 09/79 140 PS (100 kW; 140 hp) @ 5500
192 Nm (142 lb-ft) @ 3500
from 09/79 196 Nm (145 lb-ft) @ 3500
W123.086 1978–1985 250 2.5 L M123 I6 140 PS (100 kW; 140 hp) @ 5500
from 09/79 140 PS (100 kW; 140 hp) @ 5500
192 Nm (142 lb-ft) @ 3500
from 09/79 196 Nm (145 lb-ft) @ 3500
W123.030 1975–1981 280 2.8 L M110 I6 156 PS (115 kW; 154 hp) @ 5500 222 Nm (164 lb-ft) @ 4000
W123.033 1975–1985 280E 2.8 L M110 I6 177 PS (130 kW; 175 hp) @ 6000
from 1978 185 PS (136 kW; 182 hp) @ 5800
229 Nm (169 lb-ft) @ 4500
from 09/79 235 Nm (173 lb-ft) @ 4500
W123.050 1977–1980 280C 2.8 L M110 I6 156 PS (115 kW; 154 hp) @ 5500 222 Nm (164 lb-ft) @ 4000
W123.053 1977–1985 280CE 2.8 L M110 I6 177 PS (130 kW; 175 hp) @ 6000
from 1978 185 PS (136 kW; 182 hp) @ 5800
229 Nm (169 lb-ft) @ 4500
from 09/79 235 Nm (173 lb-ft) @ 4500
W123.093 1978–1985 280E 2.8 L M110 I6 185 PS (136 kW; 182 hp) @ 6000
from 1978 185 PS (136 kW; 182 hp) @ 5800
229 Nm (169 lb-ft) @ 4500
from 09/79 235 Nm (173 lb-ft) @ 4500
W123.130 1976–1985 300D 3.0 L OM617 I5 Diesel 80 PS (59 kW; 79 hp) @ 4000
from 09/79 88 PS (65 kW; 87 hp) @ 4400
169 Nm (125 lb-ft) @ 2400
W123.132 1977–1985 300D LWB 3.0 L OM617 I5 Diesel 80 PS (59 kW; 79 hp) @ 4000
from 09/79 88 PS (65 kW; 87 hp) @ 4400
169 Nm (125 lb-ft) @ 2400
W123.133 1981–1985 300D Turbo 3.0 L OM617a I5 Diesel 125 PS (92 kW; 123 hp) @ 4350 245 Nm (181 lb-ft) @ 2400
W123.150 1977–1981 300CD 3.0 L OM617 I5 Diesel 80 PS (59 kW; 79 hp) @ 4000
from 09/79 88 PS (65 kW; 87 hp) @ 4400
169 Nm (125 lb-ft) @ 2400
W123.153 1981–1985 300CD Turbo 3.0 L OM617a I5 Diesel 125 PS (92 kW; 123 hp) @ 4350 245 Nm (181 lb-ft) @ 2400
W123.190 1978–1985 300TD 3.0 L OM617 I5 Diesel 80 PS (59 kW; 79 hp) @ 4000
from 09/79 88 PS (65 kW; 87 hp) @ 4400
169 Nm (125 lb-ft) @ 2400
W123.193 1980–1985 300TD Turbo 3.0 L OM617a I5 Diesel 125 PS (92 kW; 123 hp) @ 4350 245 Nm (181 lb-ft) @ 2400

 

 

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