so i have an issue with my car that has recently started but im going to lay the ground work to remove a bunch of issues it may be. B5 A4 1.8t AWM head, 06A block,APR stage 1 tune automatic with a forge BOV SPLITTR. I had a small leak from my coolant flange and thermostat housing both of these items have been replaced and redone no leaks there anymore. now that i have no leaks i notivced i would still lose coolant on my way to work, have to put in some water into the car since the warning light came on, not coolantant(its expensive) to get to work and refill the car. after this has been happening for about a month i put the car up on a lift and ran it while it was 6 feet off the ground to see what was going on. i brought it to operating temperature, oil was around 210-220 degrees and and the water temp gauge was directly in the middle of the gauge. i held constant of about 2000 RPMM to get it to temperature, let off the gas no problem. i then swept my rev range up to 5000RPM held for 3 seconds and then let off. about 4-5 seconds after i let off the gas and let it idle a bunch of water came out the overflow portion of the expansion tank, a very considerable amount. i went down the rev range and found that if i revved it up to 3000RPM it would do te same result as if it was 5000 RPM.nothing happens at lower RPMS. so this is how i lose all my coolant/water. i have checked to see if it smells like exhaust through the expansion tank, it does not, i used a color changing liquid to see if any exhaust gas was coming through, nothing. i checked and replaced the thermostant, , none of these are the issue, oil is not milky. tried to rule out all possible things. like a head gasket or something relating directtly to the engine. it doesnt seem to be anything like this. also the headgasket and head were recently redone about 2000 miles prior with no issues. i only got issues when i developed a leaky rear coolant head flange. at this point i dont know if i have something clogged or if my expansion tank is broken or something else. any help would be greatly apreciated thanks in advance!

 

I didn't even read the whole post, but replace your brown tank with a new clear one. the cracks on the bottom of your tank are leaking - maybe.

 

i did a pressure test on the system and found that my tank was loosing the pressure, but not from the cracks in it sortof. the issue was were the cap seals to the tank the inner seal in the tank became too fat and no longer worked, i swapped the tank and reused my old cap, and its perfect.