Follow the manufacturer's torque specifications closely. For the R53, the typical torque is around 10 Nm (7 lb-ft), but always refer to a service manual for the exact specifications.

Thanks for the response...much appreciated. I have been using new seals...and meticulous about cleaning. I find various different torque numbers on the web ranging from 10nm to 15 nm. I have tried both 10 and 15. Any idea what the defintive number is?  Beyond that...., I suppose it could be a warped surface from heat cycles on the exchanger...it looks fine visually. Hate to resort to rtv but that might be were I am at this point....

Make sure the surfaces are clean, use new gaskets, and follow the correct torque specifications carefully; consider using RTV sealant for extra sealing if needed.

Having a time replacing the two oil cooler gaskets on my 06 r53... I have installed 3 times now....and it still leaks from the oil water exchanger. I have tried a range of torque nm found on the web - and still can't get it to seal properly. First time - a seal seem to creep out of the exact groves - and got crushed with torque..... Others times - I went easy on torque but still had drips. Akk - any tips on what should be an easy job?