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Engine checking refurb supplement oil filter housing thermostat

Discussion in '200 TDi' started by steve2286w, Aug 15, 2019.

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  1. steve2286w

    steve2286w Well-Known Member

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    Ive been investigating the oil filter housing thermostat operation
    and why its a bad idea if you keep in in with oil cooler pipes removed ie if you have a 200Di with no oil cooler



    200TDI Oil filter housing fitted with oil cooler pipes

    Normal Operation with cooler pipes fitted


    When cold


    1. Yellow Line – dirty oil pumped direct from sump the majority of this flow goes in 2 directions
      1. Thermostat housing hole and to LH port oil cooler supply

      2. Dirty side of oil filter via the black cable route

      3. When cold none/minimal oil will find its way in return pipe into the thermostat port/ oil cooler return port
    2. Blue line – pumped clean filtered oil feed from inside filter goes into block to lube cam and crank etc., the oil pressure switch is tapped into this line


      ------------------------------------------------------------------------------------------------

    3. The thermostat bulbs purpose is to divert oil into the oil cooler when oil temp rises and gets hot is does this by moving a steel washer to uncover ports as its heated and expands. It has a steel rod which extends when heated
      1. when cold its about 8mm long

      2. When heated 90-100C it extends to about 25mm long

      3. With the thermostat still hot this was then fitted back in housing and further pic taken

      4. Although it had cooled some by then you can see it blanked off half the hole to the dirty side of filer

      5. With the total movement about 25mm-8mm = 17mm at 100 C its likley the steel washer moves all the way across preventing sump oil flowing to dirty side of filter from the bottom of the thermostat housing but it opens up the flow route to the filter from the oil cooler return flow



        -----------------------------------------------------------------------------


        When Hot
      1. As above in 1a dirty oil flows into thermostat hole and to the oil cooler supply via the LH port-(yellow line)

      2. Cooled oil returning from the oil cooler goes into the Thermostat front oil port and directly into the dirty side of oil filter to be cleaned






    Result good oil circulation - Happy Engine




    Operation with cooler pipes removed and ports blanked off, thermostat fitted


    When cold


    1. Yellow Line – dirty oil pumped direct from sump the majority of this flow goes in 2 directions
      1. Thermostat housing hole and to LH port now blanked off

      2. Dirty side of oil filter via the black cable route

      3. Return port blanked off
    2. Blue line – pumped clean filtered oil feed from inside filter goes into block to lube cam and crank etc., the oil pressure switch is tapped into this line


      ------------------------------------------------------------------------------------------------

    3. The thermostat bulb has a steel rod which extends when heated
      1. when cold its about 8mm long

      2. When heated 90-100C it extends to about 25mm long

      3. With the thermostat still hot this was then fitted back in housing and further pic taken

      4. Although it had cooled some by then you can see it blanked off half the hole to the dirty side of filer

      5. With the total movement about 25mm-8mm = 17mm at 100 C its likley the steel washer moves all the way across preventing sump oil flowing to dirty side of filter from the bottom of the thermostat housing


        -----------------------------------------------------------------------------


        When Hot
      1. As above in 1a dirty oil flows from block into thermostat hole but ends up stuck with no flow getting to dirty side of filter with as the thermostat has covered up the route /hole into the dirty side of filter (black cable route in 1b above)

      2. There may be minimal leakage past the steel washer in thermostat bore depending on engine temperature/ oil pressure
    Result - Minimal / No oil getting through filter to supply bearings

    Action : remove thermostat if you remove the cooler pipes and blank ports off if fitting a 200Di or for other reasons


    oil flow 200tdi.jpg IMG_6511.JPG IMG_6513.JPG IMG_6514.JPG IMG_6515.JPG IMG_6516.JPG IMG_6517.JPG IMG_6519.JPG IMG_6521.JPG IMG_6522.JPG IMG_6524.JPG
     

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    Last edited: Aug 15, 2019
    lynall likes this.
  2. Blackburn

    Blackburn Well-Known Member

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    Steve the removal of oil thermostat when not fitting oil cooler is already documented in the Glencoyne guide to fitting a 200DI.
     
  3. steve2286w

    steve2286w Well-Known Member

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    true it’s a great guide but blink and you miss it! I had seen the small mention of it but there’s no explanation or warning on its removal , being a bit nosey I wanted to find out why it could be a problem if left in
     
  4. lynall

    lynall Well-Known Member

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    Just pulled the extension housing off my series tdi conversion and as I thought my stat was still fitted, even though I had blanked the ports many years ago.
    I wonder if the oil cooler is in fact full flow or just partial flow?
     
  5. steve2286w

    steve2286w Well-Known Member

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    As you don’t have the oil cooler fitted , Did you remove it , the No5 photo above shows it well , the hole in filter housing is the only route in to get oil through the filter , and as it heats up and the thermostat pushes that steel washer to the right reducing or closing flow into the filter, it may not close off completely as the oil pressure is acting with the spring force to move it to the left but resisted by the thermostat force.

    With cooler fitted normally when cold, it looks like oil still goes in cooler and returns from cooler depending on above
     
  6. lynall

    lynall Well-Known Member

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    No cooler on my series and yes Ive just removed the stat, its still truboed and intercooled but running the std very early narrow series 2 radiator and I was to lazy to sort out a different oil cooler, when I could blank it for free!
     
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