R129 Cooling Issues

Discussion in 'Engine' started by Russf123, Sep 13, 2011.

  1. Russf123

    Russf123 Member

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    Guys,
    my '97 SL500 is starting to run a little hot in traffic. She is fine on a run but as soon as stop/start running is involved, she starts to creep up to 90 degrees. So, have flushed out the coolant and changed with MB spec and changed the thermostat. I have noticed that the large, engine side fan seems to run all the time and that the 2 aux fans dont seem to be cutting in. At what temp should the aux fans cut in and is there a adjustable temperature cut in on these and is there anything else I can check?

    Thanks
    Russ
     
  2. EDZ649

    EDZ649 Hardcore MB Enthusiast

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    The 'aux' fans as you call them are for the Air Conditioning and will only run when that is on.

    90 degrees is fine, my 600 runs right up to 100 sometimes and it's nothing to do with head gaskets or anything like that, they have been done. Olly has checked it and he said it's fine........
     
  3. carat 3.6

    carat 3.6 Hardcore MB Enthusiast

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    80 - 90 Degrees sounds normal to me, the 2 "aux" fans are for the air con but will cut in if the main fan cant cope, but only as a safegaurd.
     
  4. kth286

    kth286 Hardcore MB Enthusiast

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    it could reach 120 and that would be ok.
     
  5. OP
    OP
    Russf123

    Russf123 Member

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    Ok, sounds feasible. Got a bit worried when the front wings were getting hot from the radiated heat. I know it's a big lump under there (Ooer missus!) and produces a few kW of heat but just wanted to check with the experts

    Thanks again
     
  6. AnilS

    AnilS Hardcore MB Enthusiast

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    Would the viscous coupling on the fan be weak?
     
  7. OP
    OP
    Russf123

    Russf123 Member

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    How do I test the viscous coupling?

    Russ
     
  8. grumps

    grumps New Member

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    See if their is any oily residue (silicon fluid) around the front of the coupling and if so it weak! Try running the car up to temp then let it idle with the bonnet open untill the temp is going north then get someoneto rev it to about 1500-2000 rpm and note weather or not the fan makes a rushing air noise and weather you can feel warm air rushing from the fan cowling area or cold air being drawn into the rad if not switch it off and check weather the radiator is hot from top to bottom if yes your fan is probably u/s
     
  9. colinallcars

    colinallcars Active Member

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    ^^^Will the temperature not depend on the whether?
     
  10. grumps

    grumps New Member

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    To a lesser extent yes but traffic is traffic! if your fan ain't working you still have heat to expel
     
  11. colinallcars

    colinallcars Active Member

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    Sorry - I was pulling your leg about spelling .............weather vs whether?
     
  12. AnilS

    AnilS Hardcore MB Enthusiast

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    Russ, my indy idled the engine and gently stopped the fan with a screwdriver. If the fan can be stopped, the coupling is gone or weak.

    I had mine service 2 weeks ago and he tested mine. Mine was "just" OK, but I will get a quote anyway.

    My car seems rock steady temperature wise.
     
  13. ray_hennig

    ray_hennig Hardcore MB Enthusiast

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    Don't panic ...

    To me it sounds as if you have normal temperatures. I've been in traffic today with a 300CE-24 and 32C ambient. The max I saw was 100C with 90 most of the time. Mine operates most of the time at 90.

    The aux fans do work with the A/C but will also cut in if things get hotter than 105C. There's a separate sensor that causes the aux fans to cut in. I think they usually fail open circuit and in this case the fans operate. Try to find that sensor (on mine, it's a 2-pole sensor with a plug on top) and, with the engine running, unplug it. The fans should cut in. That's the way it works for me and yours may have similar sensors, although it's 6 years newer.

    Again, your situation seems normal and you have more heat to dissipate than I.

    Relax.

    RayH
     
    Last edited: Sep 15, 2011

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