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A few weeks ago, I installed a new radiator in my car (W212 E350 CDI) without any significant problems. Since the upper driver's side hose has exhibited a minor seepage from the metal connection connecting it to the radiator, I replaced the holding clips with superior original Mercedes components and then replaced the O-rings at the ends of all three pipes. The passenger side and the lower driver’s side are completely dry; nevertheless, the upper driver’s side continues to leak. We are discussing a minimal quantity of coolant; the level is imperceptible, and there are no visible drips. However, when I run my finger along the edge of the hose, it consistently feels damp with coolant. I have emptied the coolant and removed the pipe for inspection; it appears to be in satisfactory condition. I am contemplating whether the fitting where the hose connects to the radiator is at the upper limit of tolerances, maybe being slightly oversized, which may prevent a complete seal. The subsequent stage involves applying sealant to the joint and reassembling it; allow it to cure overnight and refill it the following day. This leads me to the question of which sealant to choose. High modulus silicone is the preferred option as it is typically compatible with coolant and allows for future removal. I could utilise Sikoflex, which would ensure it never leaks; however, it would also make removal nearly impossible if I need to replace the radiator or hose in the future. Do you have any recommendations? Before anyone suggests it, I will not be removing the radiator and returning it. I might consider it if the leak were not so minuscule, but I am confident that sealant will resolve the issue. TIA

Begin with the less complex chemical for removal, then progress to the more challenging one, stating, "That will certainly resolve it."

Have you secured the hose clamp while the system was at its full operational temperature?

They lack hose clamps, which would simplify the process and prevent leaks if they were utilised. They employ these components, which are secured in position by a spring clip through a push-fit mechanism.

While I appreciate the suggestion, I would prefer to resolve the issue on the first attempt; otherwise, I incur significant expenses from the antifreeze I am appropriating from work each time I need to empty it.

Could you retrieve the coolant?

A few rotations of PTFE tape?

I doubt it will remain in position when I have reinstalled it.