300SE servicing

The 300SE didn’t come with much concrete service history.    I started a full service on the car to establish a baseline.   This will allow the car to be properly maintained to the factory schedule.    The service items arrived this week, after a quick call to MB Spares in Canberra.

Box of goodies

So far I have done the following:

  • Oil and filter change
  • Renewed spark plugs
  • Transmission oil and filter change
  • Differential oil change
  • Power steering oil and filter change
  • Removed the after market chrome wheel arch trims

Still to do, is both petrol filters, air filter and to properly flush the power steering.   This service I was only able to replace the oil in the reservoir.   I forgot to order the right oil but the oil for the rear suspension also needs replacement.   The car is fitted with rear self-levelling suspension that requires a Mercedes hydraulic oil.   This suspension is based on the design used in the Citroen DS.



Examining the car, it looks like it has been generally well looked after.  It has a new radiator and back half of the exhaust system.   It also would appear it has a refurbished or new A/C compressor.  However, from speaking to the previous owners the last service was done by an ultra-tune rather than the normal Mercedes specialist and it shows.   The car was fitted with resistor spark plugs.  On a Mercedes of this era, non-resistor spark plugs are a necessity as the leads have resistance built in.   Adding resistance via the spark plugs results in a weak spark.    The car has more power and runs better with the proper plugs.

Despite improving the car I had a setback today as the A/C stopped working.  It went from working well to warm air almost instantly.   My assumption is that the system developed a major leak, although I have not yet looked into it closely.  I checked the fuses first, to rule that out and noticed I am missing a relay.   It would appear it is for the high speed on the auxiliary fan.


I don’t know why it was removed.   I can only think that either it was blowing the fuse on high speed, or another relay that was more important failed.     Finally, I also noticed a bad bushing had caused the height corrector on the rear-self levelling suspension to disengage.  I was able to replace it temporarily until I can get a proper bushing.

Height corrector

All in all, the 300SE looks like it will be a good daily driver.    Next step is to finish the service, and fix the broken odometer.  The A/C is also important, but beyond my capabilities.

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