Elimination process nalang yan boss. First, try draining your tranny fluid, to see if its contaminated with coolant. If its not, you can have the radiator removed and cleaned (overhauled). Have the shop remove both top and bottom header tanks so that you can inspect the condition of the oil cooler tube. Easily weldable (sa MB). In your case, baka meron replacement part na binibenta.

When done, babad mo rin yung cooling system mo using degreaser soap and water mixture. Joy diluted in water is okay. Para malinis any left over oil contaminant. Use the car for 2-3 days, then drain. Fill with clean water, and drain again. Hanggang sa mawala yung soap bubbles. I would advise na tangalin mop muna ang thermostat while you're performing this procedure. Saka mo na ikabit ulit kung malinis na lahat.

OR

Baka naman kailangan mo lang talaga linisin ang cooling system mo?