Oil cooler thermostat open when cold?

[Avantus]

Hi all,

Started up my engine yesterday with a new 16row Mocal oilcooler.
Car was started cold and we noticed the cooler was leaking on a weld after 10sec or so.

But now my question is... is the thermostat in the oilfilter housing a bit open when started cold so that the cooler is always filled?

I was expecting it would take it to warm up before it would be filled.

Thanks in advance!

[Lloyd]

I believe there is always oil in the cooler.

[malncol]

my guess would be that the oilstat lets a small amount through to the cooler so as to fill it/ bleed it and also warm the oil abit!! So when it does open it doesnt dump a heap of cold oil into a hot engine??
thats my guess
mal

[Avantus]

That would be plausible then yes.

[Avantus]

A post from Johne I found earlier:

A couple of other things whilst we're on oil stats. Certainly the Mocal one and probably the internal Audi one don't actually cut off the oil flow to the cooler like a water thermostat would - the thermostat is in a bypass circuit. To work, they rely on the fact that the oil in the cooler will be cold and thus more viscous than the engine oil so the oil will take the easy route through the bypass circuit and not out to the cooler until the bypass temperature of typically 70 deg C is reached.

What that means in practice is that the cooler is always under full pressure and also will feel warm to the touch even though it's not doing much cooling - it doesn't mean the thermostat isn't working. As a consequence the cooler will get quite hot when the car is stationary.

Oil temperture closely mirrors engine temperature so if your water thermostat is old and lazy it will take longer for the oil to warm up as well.

John

Makes sense!