I am in the process of replacing the oil cooler hoses in my FC3 because one of them was leaking. I brought the old hoses to a hydraulic store and they gave me an estimate to replace the hose sections on the OEM pipes. The reason I am reluctant to have them do it is because the only size banjo fittings they have is for 1/2" hose. Does anyone know what the I.D. is on the OEM hose? It appears to me that it may be 5/8" hose (or 16 mm). I can not figure out why it would make a difference since the metal tubing and the hole in the banjo bolt is smaller than 1/2" but something tells me the engineers had a good reason for making the hose larger. Any feedback or suggestions on the issue would be greatly appreciated. I tried buying aftermarket hoses from CS and they do not fit properly at all on my vehicle.

 

You can swap out the banjo fitting and use -10 an fittings instead. Depending on vehicle they are M18x1.5 to -10 male or some are M16 I think. You can tell by the thread on the banjo bolt

The -10 is equivalent to 5/8id hose. That's what you want to use as minimum