Amanda Fitch

I've got a 2012 Q5 that started guzzling coolant two months ago. Every two weeks the "low coolant" alarm goes off and when I check the tank, it's empty. So I fill it up.

I took the vehicle into an audi repair shop two weeks ago. They tested for a leak but found no problem. At home, it doesn't leak anything in the driveway.

Engine is, not steaming, there are no funky-looking residues anywhere. My car has turned into an coolant-aholic and I don't know why. Any ideas?

m1964

is there fluid under the carpet?

if you have to fill the expansion tank repeatedly than there is a problem.
Maybe take it to the dealer (I know I will get frown upon for saying that) but they fix more Audis than any independent shop does.

MurrayA4

Amanda the first place I'd look is the water pump.When these things fail it's not always obvious or easily detectable.Unfortunately not "cheap" to fix and if that is the issue there are other things to consider doing "while they're in there" What engine do you have ?

Redd

Amanda-
In theory any good shop can find that leak. Whether it is the water pump or the head gasket or just a pinhole in the radiator, the coolant always leaves traces. A good shop can add dye to the coolant, steam clean the engine bay, have you bring it back when it is down a quart (excuse me, liter), and then use a black light to find the traces of where the leak has been. An old trick is to dust the engine bay with talc after it has been cleaned. The leak will leave clear dribble marks in the talc, which is not harmful to anything.
Or they can use a pressure tester on the system. Or use a dye test to confirm that no exhaust gasses from the engine are blowing in past a bad head gasket.
There are many ways to test, many parts to test. It could even be a pinhole in the heater core, which is leaking inside the passenger cabin.
To do it all yourself, there's a lot to look at. But carefully looking and feeling for where that coolant has gone will eventually get you an answer. A GOOD shop should know how to do all these things and will go through the whole list in the most logical or cost effective sequence. (Most shops are simply not good.)

tbennett017

Most Audis still have the under-engine cover in place. It would likely capture any drips so you might not ever see them on the ground.

Redd

My previous car also had a road pan under the engine. (One that could stay in place while draining the oil, ahem.) But over the years I found that sometimes, when you drop something and it hides in the shadows between the engine and the black pan, you can only drop the pan to find out where it is. Solution? A can of white enamel spray paint. The topside of my road pan became shiny white. Easy to clean, easy to see. With no visible outside change to the car.
Last week I dropped a small cleaning brush which tried to hide among the hoses on my Q5's engine pan. History will repeat itself.(G)

tbennett017

Yes that's a good plan. I also concur with your Talc recommendation, but I use foot powder spray, so it's easy to apply to vertical surfaces.

Amanda Fitch

Took it into the shop and it looks like it's a water pump issue. They did some tests and discovered that at one point, the water pump stopped working and a bunch of coolent gushed out. This makes sense as I was loosing coolant all at once, not slowly. Maybe it dumped out on the road and that is why I never saw it in my driveway.

The mechanic was suprised that the water pump was made entirely of plastic. We replaced it with a metal one. The whole experience cost $1300. If the problem is not fixed, and they want me to replace something else for the same price, heads are going to roll.