changing the expansion tank

5.2 V10 40v Naturally Aspirated - 429bhp
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tmg
3rd Gear
Posts: 321
Joined: Sat Apr 28, 2012 6:40 pm
Location: dublin, ireland

changing the expansion tank

Post by tmg » Mon May 25, 2015 12:56 pm

Hey

so had a suspected cracked tank. tank kept dropping to about 1/3 full pretty quickly once you had the thing filled up. but it never went lower than that. so after some checking, ordered up a new one from audi with new cap as well.

part numbers:
4f0 121 403 aa for the tank
8e0 121 321 for the end cap


fairly easy to do.

first up, take out the air intake and the airbox. its fairly straightforward, and written up a few places around the site. be careful with the small pipes on the back of the airbox -> throttle body hose!

when you have all that out, its fairly easy to take the tank out. one/two torx screws holding it in on the top, and there is on hose on top with a spring clip, and underneath, there is a pipe with a spring clip, a sensor, and the overflow pipe (see pics below).

I started with my trusty peli pump, and removed all the coolant that i could from the tank, and the pipe underneath a little too.

I then disconnected the top pipe, and the bottom sensor.

i then pulled out the tank out a little from the right hand side, and rotated it around so that it was much easier to get at the bottom spring clip with my trusty spring clip pliers thing.

wadded up a towel, and had it in place underneath before i popped the pipe off, but no fluid really leaked out. popped on the new tank, using a big flat blade screwdriver to help push off the hose from the old tank, and then put the hose & clip back in place, ditto on the top and then the screws to hold it in place. filled it back up, and put back in the airbox and pipes.

pics below:

New tank prior to install so you can see the connections underneath:
new tank.jpg
Pipe in place underneath the tank (sensor attachment is to the right, the overfilling drain to the left):
connector underneath.jpg
peli pump:
peli pump.jpg

New tank installed:
new tank installed.jpg
and lastly, old tank with cracks:
old tnak with cracks.jpg

buddyboy
Neutral
Posts: 7
Joined: Sun Nov 08, 2015 12:17 am
Location: Ireland

Re: changing the expansion tank

Post by buddyboy » Tue Nov 10, 2015 12:02 am

I wonder how that happened, Good walkthrough, im sure it will benefit others

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