Overview The 97-99 A8 is prone to two types of fuel leaks, one coming from the high pressure fuel line under the hood, and the other at the gas tank sending unit seal in the trunk. This procedure covers the high pressure fuel line under the hood. It is normally noticed during the cold winter months. The fitting leaks when very cold and fuel leaks out. It creates a smell of fuel in the passenger compartment. Once the fuel line heats up a small amount (such as after the car is turned off in the winter and the engine heat causes it to increase in temperature), it usually seals up.
Procedure Updated 12/07 with Fuel Line Repair
I performed the repair below with the epoxy on my 97 A8 about 5 years ago, and the new owner told me that he smelt leaking fuel this winter. I noticed the leak came from the other end of the hose, we cut and replaced the hose all together. I think this is a better repair and can be found below the first procedure.
Disclaimer Fuel leaks and lines are serious business. This procedure is for a repair of the line versus replacement of the entire fuel line system. The fuel lines (which are all together as a kit) from the dealer is about $800 for the parts. Then it has to be installed from the engine compartment back to the fuel tank. This procedure repairs the leak, costs about $10.00 and takes about an hour.
Audipages.com takes no responsibility for this repair! Use it at your own risk.
Supplies Required
17 mm open ended wrench
14 mm open ended wrench
Accetone or equivalent
80 grit sandpaper
Fuel resistant epoxy kit
Supplies required for repair. Make sure that the epoxy kit is fuel resistant.
Procedure
The fuel hose leaks on the high pressure side at one of the fittings. The fuel hoses are sold as one piece from the dealer, which include the supply, return and one other hose attached. It is a one piece kit that runs from the engine to the gas tank.
High pressure fuel line leak location. When it leaks, it just drips out. The fitting breaks down the pressure, so the leak is actually very low pressure.
Fuel line components.
Remove the low pressure fuel line from the fuel regulator. This is required to get proper access to the high pressure line.
Relieve the residual fuel pressure in the fuel line by cracking the high pressure line fittings. This is accomplished by using the 17 and 14 mm wrenches. Place a paper towel under the fuel line to capture the fuel that will drip.
Remove low pressure line, relieve high pressure line fuel pressure.
Remove the high pressure line, and clean with accetone. Using the 80 grit sandpaper, prep the surface by scuffing it with the sandpaper. Scuff the pipe and the fuel line fitting. After scuffing is complete, clean thoroughly with accetone.
Loosely attach the high pressure fuel line. Ensure that the angle on the line is correct for the engine plastic cover and that the low pressure line will not interfere.
Using the epoxy, place it on the fuel line. Perform this step in accordance with the instructions on the epoxy package. Let it cure in accordance with the instructions, preferably overnight. After the epoxy is cured, tighten the high pressure fittings and reinstall the low pressure line. Start the car and ensure there are no leaks. Reinstall engine plastic covers.
Completed epoxy repair. Very simple and easy.
Alternate Method Supplies and Tools Required
17 mm open ended wrench
14 mm open ended wrench
Cutting tool for fuel line connections
5/16" fuel line suitable for fuel injection systems (4 feet will do both supply and return line)
2 hose clamps per line
Procedure
Use the procedure above in addition to the procedure below. This procedure shows replacement of the high pressure (supply) fuel line only. You can also replace the low pressure (return) fuel line at the same time. Remove black plastic cover on right hand side of engine compartment to expose the other end of the fuel lines.
Using a saw or other device, cut the fuel line fitting. Cut almost all the way through it and then use a pair of pliers to tear it apart. If you do the fender side first, you can then take it to your work bench and remove the fuel rail side next in a vice or other device.
Once the fuel lines have been removed, the existing lines have barb fittings. Cut the new 5/16" fuel hose to length, put a hose clamp on each end, and slide it over the barb fittings. Secure the hose clamp (make sure it's tight). Reassemble everything and you are done!
