How to carry out replacement: Thermostat 300 SE, SEL/S320 (140.032, 140.033) W140
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Change W140 S 420 (140.042, 140.043) Thermostat yourself – manuals and video tutorials

How to change engine thermostat on MERCEDES-BENZ S-Class Saloon (W140) – replacement guide

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When to replace the Thermostat on your MERCEDES-BENZ S-CLASS
Recommended replacement interval for the part category Thermostat : 50000 km
Important!
This replacement procedure can be used for:
MERCEDES-BENZ S-Class Saloon (W140) 300 SE, SEL/S320 (140.032, 140.033), MERCEDES-BENZ S-Class Saloon (W140) 300 SE 2.8 (140.028), MERCEDES-BENZ S-Class Saloon (W140) S 280 (140.028) … 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

All the parts you need to replace – Thermostat for S-Class Saloon (W140) and other MERCEDES-BENZ models
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Tools
Replacement: engine thermostat – MERCEDES-BENZ S-CLASS (W140). Tools you might need:
Wire brush
All-purpose cleaning spray
Torque wrench
Combination spanner #10
Drive socket # 7
Drive socket # 8
Drive socket # 10
Ratchet wrench
Long nose pliers
Funnel
Fluid container
Fender cover
Buy tools
Replacement: engine thermostat – MERCEDES-BENZ S-CLASS (W140). AUTODOC recommends:
  • Check the condition of the coolant every time you replace the thermostat. Change the coolant if necessary.
  • Please note: all work on the car – MERCEDES-BENZ S-CLASS (W140) – should be done with the engine switched off.
Carry out replacement in the following order:
  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
    Unscrew the coolant reservoir cap.
    Step 4
    Lift the car using a jack or place it over an inspection pit.
    Step 5
    Prepare a container for fluids.
    Step 6
    How to change Thermostat on W140 1991 - free PDF and video manuals
    Open the coolant drain tap.
  2. Step 7
    How to replace MERCEDES-BENZ S-Class Saloon (W140) 300 SE, SEL/S320 (140.032, 140.033) 1992 Thermostat - step-by-step manuals and video guides
    Drain the coolant from the engine.
    Replacement: engine thermostat – MERCEDES-BENZ S-CLASS (W140). AUTODOC experts recommend:
    All work should be done with the engine stopped.Wait until the coolant has completely flowed out of the drain hole.
  3. Step 8
    Close the coolant drain tap.
    Step 9
    W140 S 350 3.5 Turbo Diesel (140.134) 1993 Thermostat replacement: free workshop manuals
    Loosen the clamp of the expansion tank hose. Use a drive socket #7. Use a ratchet wrench.
  4. Step 10
    Changing Thermostat on MERCEDES-BENZ S-Class Saloon (W140) 500 SE, SEL (140.050, 140.051) 1994 by yourself
    Detach the expansion tank hose from the thermostat housing.
  5. Step 11
    How to remove MERCEDES-BENZ S-CLASS S 500 5.0 (140.050, 140.051) 1995 Thermostat - online easy-to-follow instructions
    Detach the coolant hose.
  6. Step 12
    How to replace Thermostat on MERCEDES-BENZ S-Class Saloon (W140) 1996: download PDF manuals and video instructions
    Unscrew the thermostat housing fasteners. Use a drive socket #10. Use a ratchet wrench.
  7. Step 13
    How hard is it to do yourself: Thermostat replacement on W140 400 SE, SEL/S420 (140.042, 140.043) 1997 - download illustrated guide
    Remove the fastening bolts.
  8. Step 14
    Need to know how to renew Thermostat on MERCEDES-BENZ S-CLASS 1998? This free workshop manual will help you to do it yourself
    Remove the thermostat together with the housing.
    Replacement: engine thermostat – MERCEDES-BENZ S-CLASS (W140). Professionals recommend:
    Caution! Coolant may leak out of the coolant lines and thermostat housing.
  9. Step 15
    Changing of Thermostat on W140 1991 won't be an issue if you follow this illustrated step-by-step guide
    Clean the thermostat housing mounting seat. Use all-purpose cleaning spray.
  10. Step 16
    Clean the thermostat mounting seat. Use a wire brush. Use all-purpose cleaning spray.
    Step 17
    MERCEDES-BENZ S-CLASS S 420 (140.042, 140.043) Thermostat replacement: online guides and video tutorials
    Install a new thermostat.
  11. Step 18
    Replacing Thermostat on W140 1993 300 SE, SEL/S320 (140.032, 140.033) by yourself
    Install the thermostat housing.
    Replacement: engine thermostat – MERCEDES-BENZ S-CLASS (W140). Tip from AUTODOC experts:
    Be sure to use a new O-ring when installing the sensor.
  12. Step 19
    S-Class Saloon (W140) S 500 5.0 (140.050, 140.051) 1994 Thermostat DIY replacement workshop manual
    Install the fastening bolts.
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