A little background:

I just did a head swap on the car. Used impala gaskets, milled LE2 heads, high compression. Always run 91 octane. Car is tuned for a 160 stat, I have a 180 in it (couldn't find a 160 in local parts stores).

Before the headswap I had the water pump go out, so it's a new pump/stat. Cooling system was filled back up with water but still had coolant in it. Dexcool, btw. Never any problems, never went above 180.

After heads swap all the coolant is gone so I fill it back up with water to try to flush the system out nice and good and refill with dexcool later. I have a BITCH of a time bleeding the system. Took three days, 10+ attempts at bleeding it. Finally it stopped overheating and ran like it used too, never going above 180.

Two days ago I opened the rad cap to make sure it was topped off after the bleeding, and I found it a quart low. I added some dexcool to top it off. Once it got really hot 220 and I shut it down. Now the damn thing Will sit at idle (no load conditions) at around 180, WILL NOT OVERHEAT at idle. As soon as load is put on it, like accelerating from a stop light, the needle moves straight up to 200, then slooooowly moves back down to 180. It did this twice and I got scared and dumped it off. Bleeder screws only shoot out coolant.

No coolant smoke/steam from exhaust, no coolant in oil, no oil in coolant. Proper torque amount/pattern on brand new ARP head bolts with permatex applied to them. Has NOT been overheated. 220 was as high as I let it get (never hit the red zone on gauge - gauge is accurate) before I shut it down. Right now it's running mostly water, with about 2 quarts of dexcool. May have a very, very small coolant leak on the hose on the top of the wp, I see a few drops there occasionally, stock clamps are pretty weak.

Any ideas?

 

Did you keep track of how much water you've put into the system so far? You don't want to run straight water for very long or your w/p bearings will **** the bed.

 

at least 3 gals

 

Your cooling capacity is ~16 quarts. I think you are still low.

 

alright, I didn't realize these cars held 4 gallons, I thought it was just 3. I'm probably half a gallon low or so. I ordered a 160 stat from summit just for the hell of it anyway.