What happens if you rev the motor to 2,000 RPM or above? Will the temps come down at all?

I had trouble getting all the air out of my LS3 also. What I did to finally get all the air out is:

1) Raised the front of the car about 1.5-2 feet on jackstands.
2) filled the motor through the upper radiator hose
3) then filled the radiator
4) Ran the car with the front end still raised and the radiator cap off. With my dual pass radiator is was super easy to look down the open fill and see when the thermostat opened. I allowed the thermostat to cycle open and closed 3 full times with the cap off and then buttoned everything up.

No problems since.

I'm not saying you have air in the system necessarily but if you do, this is a handy tool for filling cooling systems:

http://www.tooltopia.com/uview-550000.aspx

I think I made progress last night. I pulled the t stat and it appears to work fine in 160 water. Reinstalled that and filled the system. It got hot with the cap off. I shut it off and lots of steam came out. Filled the radiator and over flow canister and started to get air bubbles out of the overflow. This only started to happen after the cap was back on the radiator. My top hose gets real hot, bottom hose not so much. I'm going to run it when I get home to see if it runs around 160. The overflow bottle was drawing fluid into the radiator After I re capped it. Should I keep coolant in the overflow? I was never able to see coolant moving. It seemed like the hoses were flimsy until I capped it. Lots of info I know so thanks for the help...

yes, keep the over flow half to 3/4 full when hot.....check the level when cold. You should have fluid in the bottle with a engine cold.
Top off the radiator. Reinstall cap. Run, let it get to normal op temp. Verify the fans run and note temp. See what the bottle level is.

Just want to keep this updated. I think the problem is coming from the proximity of the temperature sensor to the header. I'm going to use a spark plug fabric boot to insulate the sensor and see if the temp gauge stops shooting up so high.

the surface that registers the temperature is in the heat. External heat should not affect, unless you are running a capillary tube style sender.

This is the type sensor I have. This is only going to the gauge.

Agree with everything Vince said.


Overflow bottle should always have coolant in it.

Yeah, external heat should not affect that sender. I believe grounding the terminal will show hot on the gauge. Anything touching the terminal or wire? ie burnt wire shirting to ground.

How did you make out with the air and over flow situation?

Something that has not been mentioned are the heater core hoses. Are they plumbed to a heater core? Are they getting hot? The LS cooling system needs to have flow through the two hoses for the heater core.

Andrew