Driving home the other day; the temp gauge just pinned past hot. Drove the 2 minutes home and shut it down. Next day check the rad fluid and its empty. I refilled it and ran the car about 30minutes and couldnt find one drip. Drove the car for another 30 minutes and the needle stays just before the center of the gauge(norm). Wake up this morning check the level in the rad. And its halfway empty, refilled; drove to work w/ no overheating problems. WTF?

 

you may have a leak somewhere or burning coolant.
any white smoke coming out the tailpipe?

 

I'd do a compression check, not only cuz you're mysteriously losing coolant but also cuz you drove the car with the temperature gauge pegged. Aluminum heads don't like getting that hot. A dead give-away for burning coolant is, when you're doing the compression check, the gauge will have drops of water on it when you remove it.

If the cylinders are all good, do a very careful check with a flashlight around the entire cooling system. with the car running and at operating temperature, twist each of the hoses including the heater core hoses. I'd recommend gloves for this. Make sure every hose is seated well, flexes easily, and isn't cracked. You could be losing coolant though a pinhole crack in one of the several tiny hoses that sit behind the engine.

 

do the compression testers from auto parts stores work..usually go for around 30$?

 

I have a $15 one from pepboys and it works just fine.

 

check your oil for traces of coolant. that should give you your answer

 

Replaced the radiator anyway; drove for a lil bit..and the leak appeared. Wierd though, its coming from somewhere behind the motor in the back. Above the alternator, cant locate the exact location though; it is however on the right side. Anyone have any ideas as to what could be leaking?

 

..

 

When you say the leak is on the right side, is that the driver side? What do you drive? Could be a leaky water pump.

 

On the drivers side, all I can see is it is leaking from somewhere above the alternator. Where is the water pump located on the d16z6; is it a "bring it to a shop" job? If it were the headgasket, I would be able to see oil in the coolant; coolant on the dipstick; etc. Which I am not seeing.