To head gasket or not to head gasket, that is the question...

what type of gauge do you have? Is it stock? I read a lot about the stock gauges being inaccurate.

I would check the oil for coolant and coolant for oil. It would be a good idea to do a compression check as well. All cyclinders should be within 10% or so of each other...and it should be somewhere around 150psi for a stock motor.

Check to make sure that the coolant hoses aren't leaking. Also check the thermostat housing, water pump, and timing cover for leaks. If the coolant system is leaking and air is getting trapped, then your overflow will overflow.

The steps above are also a good thing to check for a bad head gasket.

Mario

did you notice any smoke? White smoke=burning coolant=blown head gasket. Sounds kinda weird for the overflow to be overflowing, but the temp isn't high. Did you burp the system when you filled it up w/ coolant? Usually you want to "burp" the system by filling it up, leave the cap off, raise the front drivers side of the car so that the radiator neck is above the thermo housing and start the car...let it run for 10-15 min and let it get all of the bubbles out and top it back off. Fill up the overflow properly (if the car is hot, probably wanna go to the hot mark).

You can compression check by buying a compression checker at the auto parts store; they're around $30 or so. Simply pull ALL of the spark plugs, screw the attachment into the spark plug hole and crank it over about 10 times or until it stops increasing. Write down all of the numbers for each cyclinder and compare. A 10% devience is ok, more than that and you have problems. When my headgaskets were blown, I was getting numbers below 50 on most cyclinders, but all prob. won't have those results.

Good Luck