i have a 89 vert. i recently installed and new metal thermostat neck and a new godspeed radiator. when i first installed these items the system built up pressure just fine. i bled the system correctly and completely 2 days after the install. about a week later i checked the fluid and i was low in the radiator and the overflow was now empty. i thought i maybe it was just extra air that didn't come out. but now i have but in about a quart of water a week for a month and i cant find the leak. my car doesn't smoke on start up or otherwise. there is no drips from my car .no water in the oil.no wet carpet on the inside.where is my water going??? any help would be great

 

Any hazy fog around the bottom of the windshield? Did you pull the carpet up? I've had pinhole leaks in two heater cores now and didn't notice it until i pulled the carpet back and found residue around the floorboard and ECU.

 

check the clamps on the radiator,water pump and thermostat neck,seeing as you just replaced it.
I have heard about hoses not fitting correctly on aftermarket rads.
My KOYO seemed to have that same problem with the hose feeling a bit loose on install,so what i did is wrap the necks of the rad with Teflon tape and then put the hose on,and clamp them.I also did the lower water pump neck and the upper thermostat neck to prevent any leakage.It has been holding for 2 years now.

 

so i took off my uim today and i found my leak under it.the nipple was rusted and chipped and the hose was cracked... finally putting in my atkins sleeves and replacing all of the vacuum lines and such...thanks for you help.