Hi, hoping someone might know the answer to this?

I've got an A7 that I've had for around a year. Its 10 years old, like the models in the link below (sorry this is the first Audi I've had - now have 2 but not up on the model years yet). Basically the issue is it periodically says I need to turn off the engine and check the coolant level. Sure enough the coolant level is low.
I had it in the garage for the fuel cap issue and they checked the coolant wasn't leaking. They said it wasn't, I haven't noticed anything under the car either to indicate a leak, if there is one it must be slow in any case as this happens maybe every 6 weeks (this is the third time it's happened). I have noticed that sometimes when I park the car the fan is going like mad.
Any ideas?
It's like the older ones on the bottom row: Audi A7s

Thanks in advance

 

Sounds very much like a leaky headgasket

 

Thanks I will ask the garage to check

 

Could very well be a headgasket, although I've never heard of that as a common failure point on the supercharged 3.0 engine.

The other possibility is a failing water pump and / or thermostat - both of which are well known, common failure points for this engine once you get up around 75,000-100,000 miles. I had the same situation as you (extremely slow coolant loss) and once we replaced the water pump and thermostat it stopped.

That said, a leaky water pump usually is accompanied by some coolant residue in the area, so if you're seeing no signs of a leak, that may not be it. A leaky water pump probably would not leak enough coolant to have visible pooling under the car, but you would probably see some signs in the vicinity of the water pump itself - likely dried coolant (which looks like dried up salt water in that it leaves a white / slightly pinkish residue - google "dried coolant residue" to see what it looks like). Here's a post with photos of where the water pump is in case you want to take a flashlight to the front of the engine and see if you can see anything (the post is about a Q7, not an A7, but it's the same engine): https://www.audiworld.com/forums/q7-...-pump-3027510/

If you think it's the water pump / thermostat and decide to replace those, you should replace the PCV valve while you're at it. The PCV is also a common failure point and doesn't cost that much to replace, but is labor intensive because it requires removing the supercharger. The supercharger will be off anyways for the water pump / thermostat, so might as well take care of it while it's accessible. You can also consider doing carbon cleaning on the intakes (walnut blasting), but this is less necessary unless you've had issues related to carbon buildup (hesitation on acceleration, running rough).

 

My 2013 A7 has started giving me the same warning, !!Coolant Low!! I check and the fluid is up to the top and I cant see leaks. After a few weeks of various other warning lights, I took it to the specialist. They say the water pump has a leak, even if there is no fluid loss, they say it failed a pressure test.
Personally I think its a faulty warning but I don't want to risk ruining my engine, so we play along for $1400. I'll let you know if it behaves when I get it back.

 

1. replace coolent cap or have the oil cooler checked out

 

Agree with acpRS3 - head gasket is not a common issue on the 3.0. The water pump has a "seep" hole that slowly leaks coolant for a few thousand miles before it finally goes; normally you can smell the coolant, in addition to seeing a little sediment around the pump. If I remember correctly, the PCV valve is cooled and can sometimes leak coolant as well. Most likely replacing the pump+thermostat+pcv will solve your problem. In my case, someone placed the clamp in the middle of a hose instead of at the end, causing a slow leak.