My '99 2.8 AHA is losing coolant -- the reservoir hits minimum after about a week of driving and then I top it off. It's about .75 liters per month.

I don't notice any weirdness from the exhaust, the heat is off because it's summer, and I don't see any obvious leaks.

There is a faint oil burning smell like when my valve cover gaskets were leaking onto the exhaust, but the smell is intermittent and not that bad.

Where should I be looking? Thinking the head gasket is starting to go..

 

Head gasket problems are not terribly common on the V6 block. Until you've looked underneath the water pump and the thermostat, I wouldn't think head gasket. Especially since you say the exhaust is clear. If you're losing .75 liters/month, I think you'd see white steam in the exhaust if it was head gasket.

 

Take a look at your oil cooler as well - coolant runs through there and you could have leaks at the line fittings there.

 

Thanks -- I'll check those areas.

 

Have you looked at the CTS? The o-ring can fail and leak. Another place to look is the secondary coolant pump (I think it's called the after run pump). It's sort of behind the alternator on the lower passenger side. Basically just look around for pink slime as an indicator.

 

There is a tool to test for exhaust gas getting into the coolant. You can buy it here. I believe O'reilly has it as a tool you can rent so you only have to buy the liquid you test with. There's a youtube video on how to use it.

 

I found the issue and fixed it:

There were cracks on the underside of the coolant reservoir. When the car was cold, or close to it, no fluid was leaking.

However, when the car was hot and the coolant tank was under more pressure, there was a drip from the underside of the reservoir. I noticed this after a three-hour drive when I parked in direct sunlight and popped the hood (saw it drip).

Got an OEM reservoir (no cap) for $29 shipped and some clamps for $2 and all is well now.

 

Where did you find an OEM reservoir for $30? They're usually closer to $60.

 

Here's the tank -- I got it from eBay: http://www.ebay.com/itm/370715003931?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

 

Yeah…not actually an OEM tank. Febi generally makes good stuff, but it's not a genuine Audi tank.