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Old 01-28-2013, 01:53 PM
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That hiss is a leak when the system is pressurized. The empty expansion tank confirms you are losing coolant and the puddles are evidence of a leak. Take the bottom pan off. Remove the fan shroud for better access. Put newspaper under the fron end. Then warm the car up and then shut it off. Look for the hissing sound. It should also be visible. Look directly above any spot on the newspaper that is wet. It should be pretty easy to find.
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