Very weird engine temperature behavior...

[Scottydoggs]

when you bleed it, you need to run the car till its hot with the rad cap off, and wait till the t-stat has opened up, open the brass screw, don't remove it, 2 or 3 turns, it will blow bubbles if it has air in it, when a steady stream of coolant comes out shut the screw, then top off the rad, and cap it. oh and put a 195 t-stat in it if you swapped it back to a 180, your not tuned for a 180 and you don't need it.

[T0pwater]

when you bleed it, you need to run the car till its hot with the rad cap off, and wait till the t-stat has opened up, open the brass screw, don't remove it, 2 or 3 turns, it will blow bubbles if it has air in it, when a steady stream of coolant comes out shut the screw, then top off the rad, and cap it. oh and put a 195 t-stat in it if you swapped it back to a 180, your not tuned for a 180 and you don't need it.

Exactly. I realized I wouldn't tune for a while, so I have the 195 in there now - this is the one giving me problems.

Also, whenever I try to let it run with the cap off, the coolant comes up too fast and I have to put the cap on to keep it from pouring out. I can try letting some coolant out and doing this, but wouldn't running it above the t-stat temp flush all the air out to the rad? I mean, 10 mins at 210, all the air will blow out and collect in the rad one way or another. Right?

That's what I did and I'm assuming I got all the air out, albeit not the common way. I can see how a pocket could get trapped in the upper rad hose, but I just checked for that and the coolant was right up to the bleed screw.

[Scottydoggs]

have you checked the water pump yet? like pull the belt and see if it spins freely and has no play in it it, try to move it from the top of the pulley to the bottom, as to check the bearing.(wiggle it side to side)

mine never over flowed out the radiator, only if you rev the engine while its open will it over flow. and if you grab a hose and punch it tight can you feel coolant moving past the pinch point? when the cap is on.

and have you replaced the rad cap yet? check the outlet of the radiator to the hose that goes to the reservoir, check to see if its sludged up, and hows the hose to reservoir tank and is it filled to the full line?, it needs to be air tight, no cracks or broken plastic at the cap of the reservoir tank.

thats about all i can think of at this time.

[BillBoost37]

Your problem is likely the temp gauge. Get a scanner on it and look at the pcm temp reading, not some analog ... "close enough" gauge that GM gave you.

While I hate the way that Ford and Dodge always put a C NORMAL H gauge in their vehicles...it's kinda better because the gauge is a reasonable reading..not a precision instrument.

[T0pwater]

I agree. The gauge is mostly crap. But in this case, I don't think it's the problem since I can sit in the driveway (with no airflow over the rad) and the temp does what it should - and the fans come on right near where they should, just using the gauge reading.

However, a scan gauge is high atop my priority list.

Any comments on Stant as far as quality?

Today on the way to work it didn't break 180. Now it just warms to 180 and stays there like I have a 180 in there...