Engine checking refurb supplement oil filter housing thermostat

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
   
   
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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
      
      
      
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      When Hot
4. 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
      
      
      
      
      
      
      

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
4. 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

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

Blackburn said:

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

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steve2286w said:

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

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steve2286w said:

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
4. 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
4. 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


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