chris.barnett.2011.a8

So, my coolant level drops randomly. Can idle in my driveway for an hour and a half with no drop and my diagnostic tool will read 192 F consistently and drop if I idle it up.

Diving it though, it will drop. Sometimes quickly or maybe 45 minutes down the road. I can top it off and be fine for some amount of time. I got home and parked it and could hear clicks like valves opening or closing and when it does the fluid level drops or rises and sounds like air pockets being pumped back in through the over flow line.

another weird thing, I drove with my diag tool watching live data. My ECT stays between 200-230 driving down the road but the dashboard sensor will randomly peg at max and say idle till car cools. But the tool still says 225-235.

i parked it and idled with the dashboard reading max and my tool reading 215 and the fans cycled like they normally would if the car was just sitting idling.

with the noises associated I was not sure if I had a pump or valve issue. I still can’t find out where my coolant is going. I switched to water for now because it was getting expensive chasing this with actual coolant.

any suggestions?

OberklasseA8

what car and motor do you have?

chris.barnett.2011.a8

2011 a8 4.2 v8

A8L_New_England

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I'm sure you know... if the coolant is being lost, then it is either leaking out or passing through the combustion chamber. The first is better than the second.
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If your system is full of air pockets, it would produce some of the symptoms you mentioned.
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If it doesn't drip, and the exhaust isn't steaming, then it needs a proper flushing and purging.
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<addendum> fwiw, sooner rather than later... too dilute a coolant will starve the components of proper lubrication
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chris.barnett.2011.a8

gotcha. There is no white or gray coming from the exhaust so I figured it was not leaking into the combustion chamber and I’m not experiencing any performance issues.

I wondered if the problem was worse because of the water and it turning to steam in the coolant system. Is that a concern?

what about the noises from the valves in the coolant system? Or whatever that noise is coming from?

A8L_New_England

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First things first. No leaks?
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chris.barnett.2011.a8

so the only drip I have found is towards the back left if your facing the car. But that water has been cold so I figured it was condensation from the AC. Is that a correct assumption? If I was seeing a leak from the cooling system, should it be at least warm to the touch?

A8L_New_England

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Back left is not part of your cooling system. Can you be more specific about how much fluid you need to top off? If it continually needs fluid added, and you have no leakage from under the front of the car, then it is going out your exhaust.
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Get a cooling system pressure test done at your favorite service facility.
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MP4.2+6.0

Actually something you can do before a pressure test, but you need some basic mechanical skills...or take it to a shop. That is, take the belly pan off and then give it a thorough visual inspection. Folks often forget the pan is always under there. It means in the field leaking fluids are often not found parked in the garage or otherwise. Instead, they collect on the top of the pan and either evaporate off or get blown off at road speed.

With pan off, first look at engine facing side of it for stains and oil. If oily, a different problem. With coolant, it leaves a pinkish white sort of stain. Look on engine side of belly pan for that. If there, match it to area of engine above and find exact leak source. Even absent something obvious on pan, thoroughly inspect engine top to bottom, front to back. Look for pinkish stains, whether whet or dry. If dry, they can be either crusty or more like cotton candy. Again, look for the pinkish hue.

Also, by summer, don't assume you can see coolant going out exhaust either. Takes a cold day to make it out more clearly, and to separate it from simple cold start norm. That's where a pressure test can help. Or backyard way--pull the spark plugs. If one looks steam cleaned compared to the others, that's the leak. Also possible coolant goes into oil. Just open oil fill cap. If milky mess, you found the problem.

A8L_New_England

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MP4, I don't think Chris is going to pull the belly pan and inspect the underside of his engine
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From his current experiences, it seems he is losing a lot of coolant, but that has ytbd / more than the belly pan would hold, it seems.
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+1 on what you said about seeing exhaust vapor on warm days... He needs to hand it over quick for testing
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Chris, do you have a good independent garage? The dealer is probably fine, but they will thin your wallet quickly
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