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3,9 V8 without oil cooler


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I have a 3,9 V8 in een Defender. It was running hot on idle. I have now fitted bigger fans en blanked off the oil cooler and now it sits at 88 degrees for hours.

The extra heat of the oil cooler adds a few degrees to the coolant. I don't have much space for an external oil cooler because I allready have a auto gearbox cooler and an aircon condensor in front of the rad.

Can the  3,9 be run without the oil cooler for normal road use? I do have a customer who's running one without oil cooler but that's an old man who does 1000 miles a year...

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I don't see why not, after all people put a 3.9 in place of a 3.5 without necessarily adding a cooler. I still wonder if there's something else going on, though. It's not exactly a hot climate up that way. 

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I don't know if you could fit it but the disco had a single radiator with engine water, engine oil and gearbox oil all in one unit. That's what I used when I put a 3.9 in my rrc but obviously it's a different shape at the front. 


If you run without just keep an eye on the pressure gauge, warmer oil will flow easier and make less pressure. Guess you could put thicker oil in? I ran mine on 20w50 anyway. 

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@Davo, yes it is strange, but I can't think of anything anymore..


I have a puma heater so it the flow of coolant will be blocked off at the heater when it is set at cold and that's not a good thing with a V8, but we don't have a thermostat fitted, so there should be flow.
But that is the last bit that could cause some strange behavior.


@cynic-al, I have a td radiator fitted. But because of the hot oil the water is hotter as well, so the temp is higher with the oil cooler in the radiator

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38 minutes ago, HoSS said:

You can, i did. But why not put one in, it only helps. I fitted a Mocal just behind the radiator (and remote filter).

My reasons:

  • More plumbing to do
  • Less space in engine bay
  • Another thing to leak, get damaged, fill with mud, or go wrong
  • Over-cool oil is as bad as over-hot oil
  • Another thing to buy
  • It's not actually needed (temperature stickers say so)
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