Hi. I have a slow coolant leak since 4 months so I have to top coolant once in while. The other day I top it , check oil etc. 1 week after, ( did not use the car for a week) I start it and let it warm for 5 min because it was -25 outside. As soon as I star to drive the coolant alarm went on so I turn around, park it inside the garage and open the hood.
I found the coolant expansion tank empty and the oil level way above the max level on the gage. What could be the problem?? If the oil cooler or the head gasket blew it should be the opposite right? Need help on this one.

 

The car is a 2007 a6 4.2 sline Quattro with 125 000km

 

If you checked your oil right after the motor had been running, it will appear to be overfilled because the oil has not had a chance to settle in the pan.

The easiest way to check for coolant mixing with oil is to remove the oil cap. If there is any kind of milky substance there, you most definitely have oil/coolant mixture that needs to be addressed right away. It would be more difficult to tell when it is -25 outside, but is there any white smoke, not steam from the temperature difference, but smoke coming out of the tailpipe? That is another indication of coolant/oil mixing.

Head gasket is definitely a possibility. Has it been overheating at all?

I'm not sure how this forum feels about posting links to other forums, but if you search the Audi World forum for a thread in the B5 S4 subforum called Head gasket(s) or worse!? (Oil & Coolant mixing!), there is a great writeup in that thread about what he did, but it turns out that it was the oil cooler AND a faulty head gasket.

 

There is no white smoke coming out of the tail pipe or milky substance around the oil cap but the oil look greyish on the dipstick. I'll start with an oil analysis to see if there is coolant in the oil. The car did not overheat either.
I'll also look a the oil cooler because my slow leak might come from there.
Thank for the b5 s4 thread

 

I'm having the same issue with a 2007 A6 4.2. Have had pressure tests, leakdown test, pressurized the cap, dye test after running, and nothing was showing up. It is showing that there is coolant in the oil though. Audi service wants to tear the head gasket out, and the independent shop wants to do the oil cooler first b/c of costs. (the oil cooler isn't covered by ext warranty, but the head gasket is....seeing that is actually the issue...if not i'm stuck with a 6k repair for nothing). Car has never overheated, the oil level always seems to be fine, no coolant smell, coolant disappears quicker when driving in the city, and there was a gooey substance on the oil cap (which was confirmed by the mixing of the fluids). Any thoughts on what to do first??? Thanks!

 

So if the Audi shop thinks it is the head gasket, why do you think otherwise? Shops love it for you to just throw money at the problem. If your Audi tech says it is the head gasket, and based on that assessment you get approval from your extended warranty to do the work, why not do it? I'm fairly certain they can't come back and say "Oh, well that actually wasn't the problem so you have to foot the bill now, even though we authorized the work." Maybe you should take some time to educate yourself on how the warranty works.

If they replace the head gasket and it still isn't the issue, then your oil cooler should be next. In that instance, you would be paying for the oil cooler either way, so why do it first if you don't need to? It is a common failure point in these cars.

 

The extended warranty won't authorize it because the tech "thinks that's the next place to check." He hasn't ever said he actually knows that's it. His concern is that I would be stuck with the bill if I authorize it, because the warranty won't. I took it to another shop to get a second opinion and they said their guess is the oil cooler. Basically I have to authorize something, and was wondering if anyone else has had the same problem.

 

The way you initially worded it made it seem like that was the official diagnosis and were unsure even at that. Given your clarification, I don't blame you. A head gasket is certainly not out of the realm of possibility, but it is unlikely. I think there are very few examples of a head gasket failing with no other symptoms. The oil cooler is a common failure point, so if you are just going to throw money at it until it is fixed, that would be a good place to start. I have read several accounts between the forums of the oil cooler being the issue.

 

Hello, Did you ever resolve your problem? I would really appreciate it if you told me what happened. Thanks. I have exactly the same problem

 

[QUOTE=hcmandog;1500176]Hello, Did you ever resolve your problem? I would really appreciate it if you told me what happened. Thanks. I have exactly the same problem


Unfortunately the problem hasn't been resolved. Had the oil cooler placed, and while it was faulty, the vanishing Coolant has continued. At that point the only option left was the head gasket. Haven't ever had that done, which I probably should, but still no overheating. Figured it would only be a couple grand more to get a new engine and was tired of throwing money at it. 40k miles later it is still running well.

Only things I've noticed is there is a slight sputter at times....can only notice if you're parked and behind the tailpipes. The you can feel it. Also, the coolant definately disappears faster in the winter.

I had recently read that there is a line going under the engine cover (according to them not the head) that can wear down, but haven't got ahold of my mechanic about it yet. Not sure if that makes a difference to anyone...I'm not a car guy myself. Hope you find out what's wrong with yours!