lyleswk

So my son had a sudden lose of coolant over the weekend. His Seattle Area indie diagnosed it as a broken fitting on the Aux Water Pump. My text back was "What Aux Water Pump?". After a little searching, I found the parts and a couple of youtube videos on replacing, but no description of why it is there. What is it's purpose? Is it on the longitudinal 1.8T also (I have never seen or read anything on the A4)?

Mister Bally

To keep the turbocharger cool after you shut off a hot engine. This prevents the motor oil in the Turbocharger from coking or worse, solididfying*. Audi has been doing this since the mid 1980's. It can double the life of a turbocharger.

You should hear it run after shutting down a hot engine when in a quite area like a garage or when the town is asleep.

* More common with fossil oil, which you should not use in your TT

lyleswk

Ah, gotcha. Do you know if the K03 on the stock A4 or 180 hp TT has an aux pump?

Vegas-roadster

My 2001 180 TT roadster did not have it. My 2004 180 TT roadster did. I'd guess 2002 when the 180 engine went to wideband AWP engine code

Mister Bally

My '01 New Beetle turbo (150 hp engine-AWP code iirc) has the auxiliary pump. Heck, my '87 5000CS turbo Quattro had one. After the 2nd OEM replacement broke (failure mode was an ultrasonic weld failed and all coolant leaks out) I just bypassed it with a copper pipe.elbow. Donated the car soon after that.

lyleswk

Hmm. Guess I will poke around under the hood of my A4 next time I'm there and see if I can find anything like that. Just wonder if the tighter confines of the transverse engines dictate it versus the longitudinal engine that has lots of space. There sure isn't any humming that I would associate with one like my Mercedes...

Thanks as always Mr. Bally.

Vegas-roadster

The afterpump noise on the 2004 TT was quite noticeable. Something I never heard on my 2001. Hence I posted here asking what it was at the time and was told about the "new" afterpump.