Because I installed a custom made and much larger intake manifold the regular/OE radiator expansion/overflow reservoir could not be installed in its original location.

However in our opinion we needed to keep the reservoir located in the same general area because it was important to make sure it wouldn’t cause any problems with the capacity for it to work properly. The reason I suspect Audi puts it that high in the engine compartment is the heater core hoses are relatively high too. The expansion portion of the tank as to be equal if not higher to make sure it won’t overflow just by the expansion and then overpressure overboard.

So we decided to come up with a tank that would keep the same overall capacity as the OE tank (~1.5 litre), keep its margin between its cold low level and its hot level and leave some upper room for overflow by leaving it at the same level in the engine compartment as the OE tank. This meant we had to build it in a vertical design (slanted) to keep it narrow and we basically located it right beside the oil Catch Can which is right around the area the OE radiator tank was located.

Like I said we had decided to build a narrow but taller tank and we decided it was going to be built of aluminium. We basically took a 4 inch in diameter aluminium tube/pipe and capped it at both ends with an outlet at the bottom, a pressure release cap at the top and with a brass fitting used for the overflow coming from the radiator.

I was happy with the end result (although we have not tested it with a hot motor yet) especially that the new aluminium tank only weighs 100 grams or 0.2 of a pound more than the OE plastic tank.


Here’s the basic information of the OE tank.




To secure the new tank to the chassis we made and welded a custom made bracket.




We then matched and welded a bracket to the tank.




Here’s a look on how the brackets mate up to secure the tank to the chassis.




Here’s the outlet that was installed at the bottom of the tank.




The receptacle for the cap.




The top of the tank with the cap receptacle installed and the brass fitting for the radiator return.




Here’s basically how it sits when secured to the bracket. The top portion and cap are above the heater core hoses and the cap barely clears the hood when it is closed.




To be able to see at what level the prestone is at in the aluminium tank we added to site gauges.




Here’s a front view of the tank. You can see the two site gauges on the side and the hose from the pressure overflow from the cap receptacle.




Before installing the tank the bracket was cleaned and painted.




A Moroso racing cap was used for the new tank. It releases at a slightly higher psi but since this is now a racing engine I’m told that’s actually recommended.




Since I don’t have the time and really want to anodize the tank but wanted it to look clean, I had it sent for a nice bead blasting.




Here’s a close up of the site gauges for the low and high levels.