Article Date: 12/06/21
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There are 3 different filter variations for the BKD housing and Engine. Make sure you purchase the correct one for your car. If you are unsure there are methods to identify them. Basically the top of the housing has a "nipple"/raised bump in the centre. If yours does, it means your housing has an internal water seperator and you need the "wide mouth" 2 hole version, if it doesn't have one, you need the 1 hole "narrow mouth" version.
If you are unsure what these are you, can read this article on myturbodiesel.com, it's a good website which shows you the versions and because VW / Audi vehicles are basically the same it makes it easier and should help you identify the one you need.
OPTIONAL STEP (Old fuel removal and inspection) - go to next step if you don't want to do this
The reason why you do this step, is to check for internal damage on the engine. If there are black spots in the fuel, that means Oil is getting into the Fuel Filter housing. If there are shiny metal bits, then your engine is suffering internal damage because something is getting through the fuel system. The most likely causes are normally failing tandem pumps, tandem pump seals, injector seals as possible causes. Don't worry about the Fuel filter, it WILL be black, and small amounts of dirt are acceptable in the Fuel, it's when you have big black puddles inside when you worry. If the fuel itself is black, then you have serious issues and shouldn't drive the car.
The above is a picture of my fuel, it's normal. I prefer to do this step, as you're doing the job anyway, and it's only a few extra mins. It's better to spot a potential problem before it happens, than ignore it entirely and cause more serious issues with your engine. I don't want to panic people, but it's better spending money on new seals and parts, than a new engine. Far cheaper in the long run. It's also a good maintenance procedure.
After you've installed the new fuel filter, you will need to use VCDS to prime the fuel pump on the engine to refill the filter housing. This helps prevent airlocks and starting issues. I made a video when I used to own my Golf MK5, the same technique applies on the BKD engine for the Audi A3. Please watch the below video to learn how to do this. If you don't have VCDS, I've given some possible options below that you can try
If you don't have VCDS, you could try the original older methods. Possible options are
If I were to choose any procedure it would be to pre-fill the filter housing with fuel. As you just need the engine to run long enough to push the old fuel back into the tank and clear an airlock. The whole point of cycling the fuel pump, is because it activates the pump which pushes fuel through the system into the fuel filter housing. Once the housing is full, the fuel (and any air) is pushed into the fuel tank where it can bleed off.
Most modern cars self bleed, but using the proper tools saves you the headache of no start issues because of an airlock. By at least filling the chamber pot on the engine, you're given the engine enough time to run and bleed out any air still in the fuel filter housing. Ideally you want the filter housing to be as full as possble. It's better to let it spill out and mop it up than deal with an air lock.