I'm pretty much out of idea's to why my car keeps overheating. LT1's are not new to me and I work on cars for a living. So basically I have whole new engine setup with 350miles on it. Everything was working fine until last week the temp gauge jumped up to 210 and then up to 260 when I was stopped. It was only about 72* outside as well. Got it home and the overflow bottle was filled to the top and splashed coolant everywhere.
So far I have replaced the radiator cap (which failed a pressure test), put in a new 160* thermostat, and flushed the cooling system about 5 times so far. Right now I switched to pure water with water wetter.

I have used several different bleeding techniques... squeezing the coolant hoses, front end jacked up, opening up the bleeder screw with the cap on or off when up to temp, and using my Spill Free Funnel with the car on to burp the air bubbles out. I was getting air out of the bleeder so eventually I realized I wasn't getting heat inside so I bypassed the heater core. Now I have a foot long of hose from one water pump fitting to the other bypassing the heater core. Finally, I'm getting a steady stream of water out of the bleeder. But of course, the temp gauge still gets up to 210 within a minute and keeps climbing to red until I shut it down.

A few facts:
-Fans turn on and are tuned for the 160* stat
-Scan tool shows temp sensor at water pump is basically the same as the sensor in the head (scan tool shows 10* hotter than the gauge)
-Only bleeder screw I have is on the thermostat housing. The one on the heater hose is removed.
-No coolant in the oil
-No coolant in the exhaust
-Radiator holds pressure
-Bled, bled, and bled some more

Things that still concern me:
-The coolant hose for the heater core circuit is a couple inches above the thermostat bleeder screw. So could air still be in it since it's the highest point? It feels like the top of that hose is cooler than the bottom, leading me to believe it has air in it.
-I may have a water pump failure even though it's brand new with the motor. I'm going to pull the water pump plate off and make sure the turbine doesn't spin freely from the shaft.
-Radiator possibly plugged up because the two main radiator hoses are not the same temperature after the thermostat should of opened up already. The driver's side hose is way hotter than the hose to the thermostat.

 

It sounds like you've pretty much covered everything. Try troubleshooting what you listed in the last part of you're thread, I can't think of anything else.

 

[QUOTE=Ralls;13823923]-I may have a water pump failure even though it's brand new with the motor. I'm going to pull the water pump plate off and make sure the turbine doesn't spin freely from the shaft.


Yes pull the thermostat out and have someone turn the engine over and check the turbine if its spinning and make sure everything is moving. LAst week my bros car did that and it was overheating, it took all of about 10 minutes to figure it out.

 

Dumb question, but is the shaft that hooks up the water pump in good condition? It's a long shot, but maybe it stripped out, and slipping.

 

Run it until the thermostat opens, drop the cooling fans so you can feel the radiator and see if the whole radiator is hot. When mine went less than half the radiator was flowing coolant.

 

Son of a bitch. Just as I thought. Pulled the front plate off the water pump and the turbine spins around freely. 350 miles on it too. The easiest thing I think I can do is get a welder and spot weld it to the center shaft. Beats pulling everything off and putting a new one on that could do it again.

 

Your positive you have good headgaskets?

 

Edit: Nevermind.

 

Ok so I borrowed a welder and welded a connection from the water pump shaft to the propeller. What was weird, was the propeller had a slight wobble to it. The shaft didn't wobble, just the propeller. In turn, that made it slightly rub against the front water pump plate so I gridded that down some. Either this is why the pump failed in the first place, or it just became crooked when it broke loose. Now everything cleared so I put it all back together. After bleeding the air out, my temps stayed at 180*. I let it idle a good 25minues. Then drove it around the neighborhood with a lot of stop signs for about 30 minutes. Never went above 185*. Then I get further and further away from my house then all of a sudden the gauge jumps up on me. Pulled over and let it cool down. Also cops were involved but that's a whole `nother story. Eventually it was cool enough that I rushed it home before it got hot again.

This morning I pull the water pump plate off and of course the propeller is loose again, wobbly and scraping against the inside of the pump. So clearly I tried and failed with this pump. I was trying to avoid removing the pump because I would have to remove my turbo which is a huge pain. I'm thinking about going electric. Never been a fan of electric pumps in the past, but it may benefit me with this setup.