Hello,

My 1999 C230 kompressor now has a leaky radiator core near the red drain plug.
I will replace it with a new radiator, but I have a question, at the radiator on passenger side (LHD),there is a hose attached to the radiator, is it for the coolant lines of the transmission oil cooler or the transmission oil itself?

where is the location of the cooler for transmission oil?

any response would be much appreciated.

 

The smaller rubber hose goes to the bottom of the expansion tank. The radiator pressure cap is on the expansion tank and that hose sends coolant into the system, both when filling and returning coolant. The transmission cooler is built into the radiator itself. The lines are the two metal ones on the side of the radiator. If your transmission filler cover still has a black locking clip the odds are the fluid hasn't ever been changed. All the aftermarket clips I've seen are red. Now might be a good time to change your tranny fluid and filter since you have to drain it to replace the radiator. All As always, it's good to use a quality replacement radiator and replace any bad or brittle hoses.
The radiator on your car isn't extremely difficult to replace. You don't have to pull the A/C condenser but you do have to unscrew it from the radiator, after removing the electric fans.