Radiator Oil Cooling Function - Defender Source
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Old May 15th, 2010, 07:28 AM
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Daniel Hayes
1994 Defender 90 Soft Top
Join Date: Aug 2005
Location: Boulder, CO
Posts: 129
Radiator Oil Cooling Function

How much of the cooling of the engine is accomplished by the oil cooler? How is the oil cooler integrated into the radiator? Is oil cooled by the water that has been cooled by radiator (the oil lines are on the return side of the radiator), or does the oil cooler have its own horizontal air cooled tubes like the water/antifreeze mix?
94D90 NAS 3.9 LT77 LT230T Soft Top

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Old May 15th, 2010, 07:59 AM
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Trevor Griffiths
85 110, 92 110, 92 RR, 06 LR3
Join Date: Jan 2008
Location: Elizabethotwn, PA
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Fluid to Fluid with the oil cooler passing the hot oil through a tube inside the radiator. the engine typically runs around 195* and oil tends to get a little hotter than that, so there is some heat exchange. It must work as the Rover engineers deemed it necessary, but I wonder just how much long term effect it really has.
Maybe using fluid to fluid keeps the trans or engine oil temperature range under control. If it was air to fluid, on cold days the returning fluid would be much colder and on hot days the opposite.
I'm a mechanic, not an engineer, so these are just opinions!
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Old May 16th, 2010, 11:45 AM
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Bill Adams
66 109 sw 94 lwb
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I asked the same question on another section of this forum and the consensus is that the oil cooler is not needed. The engine oil can't get hotter than the rest of the engine or else we have a huge problem with the laws of thermodynamics.
Bill Adams

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Old May 16th, 2010, 01:47 PM
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Scott Y
95 D90 SW, 2003 Disco II, 93 D110
Join Date: Feb 2009
Location: Arizona
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After replacing oil lines in a D-90 SW last year I ran the truck last May in the AZ heat. Checking the temperature difference between the cooler intake and exhaust, the difference was only about 10-15 degrees. Also, our 03 disco II does not have an engine oil cooler. Maybe you need the cooler if you are towing a lot of weight, up steep mountain roads, etc. Don't think it is required for round the town, or non-stressful driving.
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