= check your water pump I worked in a shop and we had an older Honda Civic with = same problem. After much pulling of hair and curseing figured out blades on = water pump had rotted off and car had to be spinning at 3000 rpm to get enough = coolant flowing to cool car because of the rotted away W/P blades. Something to = check, and the po might have flushed coolant before trying to solve problem so = coolant might look good but been realy bad before.