Oil in cooling system

[Passat my07]

So I’ve got oil in the coolant. (07 Passat 3.2 vr6). Is there anything common that fails? It smells a bit like dsg fluid but hard to tell. I took the dsg filter cover off and there isn’t any evidence of water in the trans. Also no evidence of water in the engine.
I guess the options are trans cooler, head gasket, engine oil cooler (if it has one)?
Any thoughts?
Thanks.

[Old Navman]

Both head gasket and trans cooler could be the problem. I think there is also an oil cooler tank built into the radiator which could explain oil in the coolant. Try doing cooling system pressure test, if you don't have the gear just visit your friendly radiator repair service - they will surely have the tool. Or you might want to invest about $60-70 and get your own from for example Dxxk Smith - 15Pcs Radiator Pressure Test Set Cooling System Leaking Check Refill Vacuum Tool.

[Passat my07]

I don’t really want to put pressure in the system as I might push the water into the trans. I think I’m going to replace the trans heat exchanger because if water gets in there it’ll probably damage the mechatronics. I might drain the dsg too and see if any water comes out.