zenfrogmaster

I tracked down a leak on my 2002 C320 wagon to the upper fitting on the transmission cooler. Not knowing the size, I got a new o-ring from the dealer, popped the clip, and replaced it.

Same leak, tried some slightly fatter o-rings (didn't fit), and made sure that everything was absolutely clean. No luck. The hose can move a but even when everything is buttoned up.

This can't be that difficult, so I must be missing something obvious - wouldn't be the first time.

Thanks in advance for your help!