When to replace the Thermostat on your MERCEDES-BENZ 123 SERIES
Recommended replacement interval for the part category Engine thermostat : 50000 km
Important!
This replacement procedure can be used for:
MERCEDES-BENZ W124 Estate (S124) 250 TD Turbo (124.188), MERCEDES-BENZ W124 Estate (S124) 300 T Turbo-D 4-matic (124.393), MERCEDES-BENZ W124 Estate (S124) 300 T D (124.190), MERCEDES-BENZ W124 Estate (S124) 300 T D (124.190), MERCEDES-BENZ W124 Estate (S124) 250 T D (124.185), MERCEDES-BENZ W124 Estate (S124) 250 T D (124.185), MERCEDES-BENZ W124 Estate (S124) 200 T D (124.180), MERCEDES-BENZ W124 Estate (S124) 200 T D (124.180) View more

The steps may slightly vary depending on the car design.

This video shows the replacement procedure of a similar car part on another vehicle

Tools
Replacement: temperature sensor and engine thermostat – MERCEDES-BENZ KOMBI Estate (S124). Tools you'll need:
Wire brush
All-purpose cleaning spray
Dielectric grease
Torque wrench
Combination spanner #10
Combination spanner #19
Drive socket # 7
Drive socket # 10
Drive socket # 22
Ratchet wrench
Flat screwdriver
Funnel
Fluid container
Fender cover
Replacement: temperature sensor and engine thermostat – MERCEDES-BENZ KOMBI Estate (S124). AUTODOC experts recommend:
  • Check the condition of the coolant every time you replace the thermostat. Change the coolant if necessary.
  • All work should be done with the engine stopped.
  • All work should be done with the engine stopped.
Replacement: temperature sensor and engine thermostat – MERCEDES-BENZ KOMBI Estate (S124). Take the following steps:
  1. Step 1
    Open the bonnet.
    Step 2
    Use a fender protection cover to prevent damaging paintwork and plastic parts of the car.
    Step 3
    How to change Thermostat on Mercedes S124 (W124) 1985 - free PDF and video manuals
    Loosen the air filter hose clamps. Use a drive socket #7. Use a ratchet wrench.
  2. Step 4
    How to replace MERCEDES-BENZ W124 Estate (S124) 250 D 2.5 (124.185) 1986 Thermostat - step-by-step manuals and video guides
    Remove the air intake hose.
  3. Step 5
    Mercedes S124 (W124) 300 3.0 Turbo Diesel (124.193) 1987 Thermostat replacement: free workshop manuals
    Cover the throttle body with a microfibre towel to prevent dust and dirt from getting into the system.
  4. Step 6
    Changing Thermostat on MERCEDES-BENZ W124 Estate (S124) 300 D 3.0 (124.190) 1988 by yourself
    Unscrew the coolant reservoir cap.
  5. Step 7
    Lift the car using a jack or place it over an inspection pit.
    Step 8
    How to remove MERCEDES-BENZ 123 SERIES 230 TE 2.3 (124.083) 1989 Thermostat - online easy-to-follow instructions
    Prepare a container for fluids.
  6. Step 9
    How to replace Thermostat on MERCEDES-BENZ W124 Estate (S124) 1990: download PDF manuals and video instructions
    Open the coolant drain tap. Use a flat screwdriver.
  7. Step 10
    How hard is it to do yourself: Thermostat replacement on Mercedes S124 (W124) 230 TE Cat (124.083) 1991 - download illustrated guide
    Drain the coolant from the engine.
    Replacement: temperature sensor and engine thermostat – MERCEDES-BENZ KOMBI Estate (S124). Tip:
    All work should be done with the engine stopped.Wait until the coolant has completely flowed out of the drain hole.
  8. Step 11
    Need to know how to renew Thermostat on MERCEDES-BENZ 123 SERIES 1992? This free workshop manual will help you to do it yourself
    Unscrew the coolant drain plug on the engine block. Use a combination spanner #19.
  9. Step 12
    Changing of Thermostat on Mercedes S124 (W124) 1993 won't be an issue if you follow this illustrated step-by-step guide
    Drain the coolant from the engine.
    AUTODOC recommends:
    All work should be done with the engine stopped.Wait until the coolant has completely flowed out of the drain hole.
  10. Step 13
    MERCEDES-BENZ 123 SERIES 250 D 2.5 (124.185) Thermostat replacement: online guides and video tutorials
    Screw in the coolant drain plug on the engine block. Use a combination spanner #19.
  11. Step 14
    Replacing Thermostat on Mercedes S124 (W124) 1986 250 D 2.5 (124.185) by yourself
    Close the coolant drain tap. Use a flat screwdriver.
  12. Step 15
    W124 Estate (S124) 230 TE 2.3 (124.083) 1987 Thermostat DIY replacement workshop manual
    Clean the thermostat housing fasteners. Use a wire brush. Use all-purpose cleaning spray.
  13. Step 16
    How to change Thermostat on MERCEDES-BENZ W124 Estate (S124) 1988 - tips and tricks
    Unscrew the thermostat housing fasteners. Use a combination spanner #10. Use a drive socket #10. Use a ratchet wrench.
  14. Step 17
    Step-by-step recommendations for DIY replacement Mercedes S124 (W124) 1989 230 TE 2.3 (124.083) Thermostat
    Remove the fastening bolts.
  15. Step 18
    DIY replacement of Thermostat on MERCEDES-BENZ W124 Estate (S124) 300 TE 3.0 (124.090) 1990 is not an issue anymore with our step-by-step tutorial
    Loosen the coolant hose clamp. Use a drive socket #7. Use a ratchet wrench.
  16. Step 19
    How to change Thermostat on Mercedes S124 (W124) 1985 - free PDF and video manuals
    Detach the coolant hose.
    Replacement: temperature sensor and engine thermostat – MERCEDES-BENZ KOMBI Estate (S124). AUTODOC recommends:
    Be careful! The coolant may leak.
  17. Step 20
    How to replace MERCEDES-BENZ W124 Estate (S124) 250 D 2.5 (124.185) 1986 Thermostat - step-by-step manuals and video guides
    Remove the thermostat together with the housing.
  18. Step 21
    Mercedes S124 (W124) 300 3.0 Turbo Diesel (124.193) 1987 Thermostat replacement: free workshop manuals
    Clean the thermostat housing mounting seat. Use a wire brush. Use all-purpose cleaning spray.
  19. Step 22
    Changing Thermostat on MERCEDES-BENZ W124 Estate (S124) 300 D 3.0 (124.190) 1988 by yourself
    Remove the thermostat.
  20. Step 23
    Clean the thermostat mounting seat. Use a wire brush. Use all-purpose cleaning spray.
    Step 24
    How to remove MERCEDES-BENZ 123 SERIES 230 TE 2.3 (124.083) 1989 Thermostat - online easy-to-follow instructions
    Install a new thermostat.
  21. Step 25
    How to replace Thermostat on MERCEDES-BENZ W124 Estate (S124) 1990: download PDF manuals and video instructions
    Install the thermostat together with the housing.
  22. Step 26
    How hard is it to do yourself: Thermostat replacement on Mercedes S124 (W124) 230 TE Cat (124.083) 1991 - download illustrated guide
    Install the fastening bolts.
  23. Step 27
    Need to know how to renew Thermostat on MERCEDES-BENZ 123 SERIES 1992? This free workshop manual will help you to do it yourself
    Tighten the thermostat housing fasteners. Use a drive socket #10. Use a torque wrench. Tighten it to 12 Nm torque.
  24. Step 28
    Changing of Thermostat on Mercedes S124 (W124) 1993 won't be an issue if you follow this illustrated step-by-step guide
    Attach the coolant hose.
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DIY MERCEDES-BENZ W124 Estate (S124) Thermostat replacement - online guide
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