My son's 155,000 mile 93 SI has gradually been using more & more
antifreeze. It recently went through a quart in 600 miles. I have
thouroughly inspected for leaks and can find none. Water pump is fairly
new and no leak at the weep hole. No sign of antifreeze in oil, no foam in
valve cover. No sign of antifreeze in the transmission fluid. No smoke or
steam from exhaust. No antifreeze smell inside the car like a heater core
leak.

The only thing I see is a very slight greenish tinge on all 4 spark plug
ground electrodes. Is there a gasket some where or a known problem where
antifreeze could be getting drawn in through the intake tract? The car is
in great shape. I need to get this figured out before it gets worse.