I have a 99 Audi A4 Quattro 2.8L with a strange coolant mystery. There is a leak at the bottom of the front of the engine where there are some hoses running across the bottom. Normally there is no leak. The other day the coolant was leaking so I topped off the resevoir and all the water ran out of the area of the leak onto the ground. The engine cooled, I added some more water to the resevoir, nothing leaked out the bottom and I drove it for 30 miles with no leak. Then I topped off the resevoir again and it only lasted a few miles. It doesn't seem to be a bad hose, is this something to do with the coolant pressure and how I have been adding water to the system. I had a bad hose a few weeks ago, fixed it, topped up the resevoir with water, and put 500 miles on it with no trouble and now this. Is it just a hose behaving badly or is it something else?

 

Are you saying you know the leak originates at those hoses, or just that coolant appears there? I ask because a leaking water pump might drip to that point, or a leak in the hoses right above the oil cooler might also drip to that point.

 

my thermostat housing just gave me the same effect, 2.8 a4 quattro. the previous owner told there was a leak and i couldnt make it happen so i thought he was a dumbass until it started flowing on me, lost 7o bucks worth of g12 on that mistake

 

I removed the front of the car and as much of the front of the engine as I could without a camshaft holder and a crankshaft locking tool. The water is definitely coming from the water pump/thermostat area but couldn't get any deeper into it. I put everything back together, filled up the system with water so I could move the car. I started it up and now it isn't leaking anything. I have put 150 miles on it and it hasn't used a drop of water. I think it is the thermostat housing. Timing belt and associated idler is new, as advertised by previous owner. Why would you change out the belt and not get the water pump and thermostat w/ housing? Dunno.

 

It's really, really dumb to do the t-belt w/o doing the water pump & stat. Most people dont change the stat housing though. Its kind of pricy and shouldn't go bad. I've done rhat job with a bargain stat gasket that didn't seal well. Some of the cheap kits include a flat stat gasket instead of the OEM o-ring. I also had to change a stat housing once because the gasket surface got nicked up.

Bottom line, sounds like you're heased back in there. Might as well do it on a fall Saturday when you planned it instead of waiting till a January Tuesday afternoon surprise.