Question about 1999 Saturn SL
A vacuum leak would appear at all times. If this happens when the weather gets cold, you should be looking at your thermostat and/or temp. sensor. I had to replace both on my car, which solved the high idle problem. First, the temp would take FOREVER to come up, which was caused by a bad sensor. Second, it'd never go above 1/4, which was due to a bad thermostat. The stock thermostats in these cars have an unnecessary rubber gasket that goes bad on the little valve that opens and closes. When it cracks and falls off, it makes for holes where the coolant can leak past. Aftermarket thermostats do not have this unnecessary gasket. Also, replacement thermostats come pre-mounted in a new housing, so there's no need to remove the old thermostat from its housing (difficult--press down on STRONG spring and turn..somewhat dangerous, too).
To diagnose your car, get a meat thermometer. Drive around for at least 15 minutes, if not longer (longer is better). Park car with engine running. Place meat thermometer in overflow tank. Dash gauge should be reading between 1/4 and 1/2, and meat thermometer should read at or above 180 degrees. If thermometer is above 180, but dash gauge doesn't go above 1/4, then sensor is bad. If meat thermometer is below 180 degrees, then thermostat is bad. Also, if dash gauge takes a really long time to come up (longer than 10 minutes), then sensor is bad. Meat thermometer should read above 180 degrees and dash gauge should read between 1/4 and 1/2. Idle won't come down completely until the gauge registers somewhere between 1/4 and 1/2. If the gauge never gets above 1/4, idle will stay quite high.
Posted on Dec 10, 2008
Sounds like you have a vacume leak
Posted on Sep 11, 2008
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