Owners of 2001-06 Audi models may come into your store with what they think is a small leak coming from the coolant reservoir. In reality, reports Audi, the leak is probably emanating from porous, hairline cracks in one or both coolant hoses just where they connect to the reservoir. The cracks are usually on the inside of the hose, which is why troubleshooting can be problematic.
To make an accurate diagnosis, connect a pressure gauge and pump the cooling system up to 15 psi. The illustration above shows the two hoses at the reservoir. One goes to the radiator, and the other to the engine. If the gauge doesn't hold pressure, take a close look at both of these hoses. You'll probably see a slight coolant leak or bubbles where the hose connects to the reservoir.
The fix is pretty obvious: Replace the leaking hose, fill the cooling system, make sure the pressure cap relief valve is working properly, start the engine and check for leaks.
"Factory Fixes" is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via e-mail at [email protected].