Another day, another issue on my 2002 Audi TT. If you own a Mk1 Audi TT, you’ve probably got your hands full with issues under the hood. The most common problem considering these cars are about two decades old now is aged rubber hoses in the engine bay. OEM rubber hoses are an ideal replacement for these hoses, but using universal hoses tend to be more economical and can still be decent replacements.
One issue I found on my car are these deteriorated, cracked fuel hoses that run to the fuel rails. These fuel hoses are the fuel rail supply and return hoses. These two hoses come together as one part with the part number: 8L9 133 986 C. Unfortunately, they are harder and harder to come by these days, so I decided to purchase universal fuel hoses to replace them with.
Parts & Tools Needed
Wire Harness Tape: XFasten Wire Harness Tape, 3/4-Inch x 50-Foot (5-Pack)
Pipe Cutter (for cutting hose): Bates- PVC Pipe Cutter, Cuts up to 1-1/4″
Hose Clamp Set: TICONN 40PCS Hose Clamp Set – 1/4”–1-1/8”
Pliers/Cutters: AKIHISA 9 inch Ear Clamp Pliers / Klein Tools Diagonal Cutter
Universal Rubber Fuel Hose: 5/16 Inch (8mm) ID Fuel Line Hose 10FT
If you measure the inner and outer diameter of the two fuel hoses, they come out to be about 1.4mm ID (inner diameter) and 8mm OD (outer diameter). When you buy universal fuel hoses, they are usually sold by the outer diameter– in this case, you’ll need to replace the hoses with an 8mm fuel hose.
How to Replace the Fuel Supply & Return Hoses
First off, your vehicle should be off when doing this work. If the car is off, then there the fuel system will not be under pressure and you can remove the fuel lines. There will still be some fuel spillage due to the fuel in the lines, but it will be minimal. Have a rag underneath when you’re removing the fuel lines.
If you have the 225 hp variant of the MK1 Audi TT, you’ll need to get the charge pipe out of the way before proceeding with the fuel hose replacement. Otherwise if you’ve got the 180 hp version, you can continue with the tutorial below.
On the top side of the fuel hoses, there are quick releases for these lines, but from my experience, they were difficult to remove. It was easier to just replace the hoses by unclamping them from the quick releases. These clamps can be tough to get off, but you can get it removed by using ear clamp pliers to squeeze them and pulling them off. Or you can use these pliers (diagonal cutters will work too) to basically bend these clamps apart. Once you are able to get these clamps off, you can remove the hose by pulling them off.
Keep in mind that there is one hose that is the fuel supply line and another hose that is the fuel return line. You should be able a small arrow on the metal line that the hose connects to, which indicates the direction of the fuel flow. This will in-turn tell you whether it is a retun or supply line.
I highly recommend labeling the hoses and connections so that when you reinstall them, you guarantee that you install the new hoses to the correct places. After the clamps are removed or twisted out of the way, you can use a hose remover tool or just pull them off.
Next, you’ll go to the fuel rail side and do the same thing. Remove the clamps, and pull the hoses off. Label these if you need to so that you can put them all back in their correct places later.
Now, take the new universal fuel hose and measure out the same lengths as the old ones by matching it up side-by-side. Follow the bends of the existing hoses and you should be able to get the same lengths (even if the universal hoses aren’t bent). To cut, you might be able to use a utility knife, but the best clean straight cut will be had with a ratcheting pipe cutter tool.
With the two new cut fuel hoses and new worm drive clamps, reinstall them onto the quick clamps as shown.
Now, we need to get the bends on the hoses since they aren’t pre-bent. To do this easily, simply bend the hoses and then use wire harness tape to wrap it. As you bend the hoses and wrap the two hoses together, the tape will help hold the desired shape of the hose.
Then, go to the other end and make sure you are connecting the correct hose to the correct return/supply line. After you connect the hoses to the fuel rails, double-check that you’ve connected the hoses correctly. Then, you can tighten up the worm-drive clamps on both ends snug. Then, you can wrap the adjacent hose to the already wrapped fuel hoses just to keep them all together.
And that’s what it takes to replace the fuel return and supply hoses on the Mk1 TT. As long as you get universal fuel hoses as replacements for your old ones, you will end up with a proper replacements. The only difficulty you might have is getting the bends on the hoses, but bending them and wrapping them at the same time accomplishes this goal.
