[Lawrence84]

A friend of mine has a small oil leak on the back of the radiator (upperside)
He would like to personally check it out..
And now I ask if somebody can give advice on how to get a clear look behind the radiator.

Thanks in advance

 

[Secret Squirrel]

You might be able to see what you're looking for with a small telescoping inspection mirror. I've used one many times to see in tight places. If you're trying to see the back of the top radiator behind the cooling fans it's going to be difficult without taking the fans off the radiator.