ryoung

The leak could be significant when you're driving, but once you park, the motor cools, and the leak stops. All you might see in the morning is a few drips.

You might try topping up the coolant level and look for leaks while the car comes up to normal temperature as it's just idling in the driveway.

pka2112

I thought about that. The spots in my garage seemed worse after a day of heavy driving. BUT...I still cant figure out exactly where its coming from. Any thoughts?

PaulW

....was the guy with a S8, who had the oil cooler go in the radiator and when the car cooled down, the coolant leaked from inside the radiator to the transmission hydraulic system through the cooler.

ex-a8drifter

most likely the fitting for the hose at the top might be cracked. You should also see white spots where the coolant leaked and dried. My coolant expansion tank had that cracked at the fitting and had the same symptoms. I replaced the tank at 50 bu cks or so from a parts store. Its an easy DIY replacement.

pka2112

If the last fill doesn't solve my problem, I'm thinking its something along these lines. The problem seems to be most prevalant after extended driving. Is this a full radiator replacement? Is the fluid getting into someplace its causing more damage?

PaulW

and drain and fill tranny a few times if it's contaminated with coolant.

tozoM8

So you would have tranny fluid in the coolant sooner that coolant in the tranny. When you cold start the car, you have tranny fluid pressure right away, but no coolant pressure. So if there is a hole, it would leak towards the coolant system, but hey you never know.

PaulW

We had this discussion before, after you shut your car down, the ATF will no longer be pressurized, but the coolant will be until the engine cools down......that's when it leaks back.

A guy had this problem years ago with his S8.