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Matt, Mechanical Engineer
Category: Audi
Satisfied Customers: 22893
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I’ve noticed a chalky substance building up on some pipe wok

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Hi I’ve noticed a white chalky substance building up on some pipe wok at the back of the engine on my 2014 Audi A8L 3.0 Diesel. It’s causing some smoke as it’s touching the manifold and there’s an ammonia odour. Any ideas what’s the likely cause.
Assistant: How old is the engine? And when was it last serviced?
Customer: Car is 4 years old and serviced recently. Adblue refill warning for 2400 km has come up on display. Related??
Assistant: What is the model of your '14 Audi?
Customer: A8L
Assistant: Are you fixing your vehicle yourself? What have you tried so far?
Customer: Nothing at present
Assistant: Anything else you want the mechanic to know before I connect you?
Customer: No that’s about it. No warning messages on the dashboard.


this sounds like corrosion to me, with water / coolant leaking out of a pipe in a very slow 'weep' this will then oxidise on the outside of the pipe and create a white powderlike deposit

I'd suggest checking the state of the pipework and rubber hoses for signs of coolant leaks

often you can make a repair by removing the pipe and cleaning it up with a wire brush and then use a 'jubilee ' type clip that you can tighten up more than the spring band type

Matt and other Audi Specialists are ready to help you
Customer: replied 4 months ago.
It’s the hose leading to the Adblue injector into the exhaust manifold. It’s perished and the garage has it in order.