filled my coolant reserve about a week ago. i checked it again today and it was barely even on the dipstick. it was probably a bit less than 1 liter worth of coolant, but its still a lot. it never leaked onto the ground, nor did it have any sign of leaking. any ideas on what it could be? TIA

 

I have the same exact problem. I had all coolant hoses replaced about a year ago and now coolant is disappering. I think my O-rings are about to go.

 

You should replace your radiator hoses, check the ast, and replace the ast cap with a high pressure cap. That fixed my coolant leak problem that I had. Now everything is back to normal.

 

are you getting any white smoke from your tailpipe?

 

no white smoke from tail pipe. im swapping the AST out at the end of the week, so we'll see how that goes. thanx for the replies

 

Are you running a stock turbo? How many miles on the engine? There are two hoses that attach there and are known for small leaks that are a bitch to detect. Have these hoses ever been replaced?

 

stock turbos...82k miles

 

Ok, rent a radiator pressure tester (Auto Zone has them or check around). You'll need to buy an adaptor for your car ($20) and hook it up to the top of your AST tank. Pump it up cold and continue to pressurize it over a period of 24 to 48 hours, it will slowly leak down. Check the AST tank for weeping around the seams. Look under your car for leaks. Keep pumping it up every few hours. Buy a mechanics stethescope ($10) with a metal extension tip and stick it down in front of your turbos close to the engine, keep probing around deep to different spots. If you hear a hissing odds are it's one of the two hoses, replace both with OEM - they're cheap and they have some peculiar bends to them. They are kind of a pain in the *** to replace but you can do it with a pair of long, curved tip needle nose hose pliers. Make sure you clean the pipe nipples with emery cloth to remove any oxidation (there will be some) before you put the new hoses on or they'll leak.
The good news - this is a very worthwhile reliability mod even if this is not your problem and is cheap to do. I guarantee you the hoses are as hard as rocks. If you bend them, they'll snap!
The bad news - this may not be your problem, or it could be one of several, ie: radiator end tanks weeping, bad coolant seals, hose, etc. As long as your car starts right away and does not blow any white smoke after 2 days of pressurization your coolant seals are PROBABLY ok. But it does seem that even the best looked after seals go at 60 to 80K. Good luck! PM me and let me know what you find out, this takes some patience and detective work.