There is an old style metal radiator cap with an overflow tube sticking out toward the firewall at the back of the V12 TT (M285/M275). There are ridges that would accept a drain hose, but there is no drain hose that I could find anywhere nearby. Something has flowed out of this relief tube in the past and has dried into a crusty, white powder. Is the V12 TT supposed to have a drain hose for this relief tube?

 

That's the charge cooler filler.

 

Thanks for pointing out the Tech Talk Forum for M275. According to these diagrams, the Charge Filler Neck does not get a drain hose...

 

Yes, there's no drain hose.

The secondary / low temperatures / charge cooling system should run pretty cool, and never get near boiling over. It kind of suggests the IC pump isn't working.

The system will also need filling, which is waaaay difficult.

Nick

 

here is is a detailed write up how to install an overflow tank onto that drain hose for $30
https://mbworld.org/forums/m275-v12-bi-turbo-platform/562924-intercooler-circuit-overflow-reservoir-2.html