I am with that guy... how hot is it getting? There are no visible leaks or similar, so maybe it just needs to be bled? Bad air bubble or something?

 

This is what I would be looking for. Once the motor has a good heat cycle recheck coolant level. Run and re test until all air has escaped and it quits taking coolant.

 

it went from 200- 245 in about 1 minute and a half. How do i recheck coolant? am i suppose to let it get hot with radiator cap off cause coolant starts shooting everywhere after five minutes of running.

 

Let air bleed out at the crossover tube near the throttle body.

 

Also make sure your thermostat isn't in backwards, sticking or something as simple as that too (if it was touched/replaced).

 

Having the thermostat in backwards will cause the same issue as RS777 stated because the coolant is trapped in the block.

After the car has been run and has cooled down where you can hold the palm of your hand on the cap take it off. This is to make sure that you don't get burned. Then see if you need to add water.

Are you sure that your gauge is working? When the gauge spikes to 200-245 range can you hold on to the coolant hoses?

Feel the water inlet and outlet and see if they are the same temp.

 

Yes use coolant pressure tester and would be help.. That picture looks like not cracked.

 

Look closely at his pic...

 

Is it possible to put the thermostat in backwards on LS1's cause it was changed about 2 weeks before it started doing this. I also bought a new water pump and just swapped over the thermostat. I dont think its possible to put in backwards cause it is a whole assembly. can a thermostat come defective or get stuck after once or twice of overheating?

 

Is the crossover tube the 3/8 rubber hose that goes from radiator to the throttle body?

 

I had my scanner hooked on to it but didnt check it to see if it was same temp the gauge said, coolant sensor is new. I just felt the top hose and it felt like it had more than normal pressure in it so it was a little hard to squeeze and you could feel like water spitting through it to get to the radiator. are the two hoses suppose to be same temperature?

 

Update! after reading everyone's answers. I started searching on how to properly bleed an LS1. Unhooked throttle body hose that goes to the little metal pipe that bolts to cylinder head and filled radiator until full. ( I saw a lot of air bubbles come out of the metal pipe but hardly coolant or air out of rubber hose coming from throttle body. Ran engine for about twenty minutes at idle and only revving it every 3-5 minutes. temp would go from 210 to 225 then go right back down to 210. I'm hoping that was the problem all along cause I wasnt aware of how to properly fill cooling system. Thanks everyone for your help. Makes me feel a lot better to return the car back to my brother in law working. will keep bleeding until no more water goes in. I'll keep you guys informed of how it goes. Thanks!!!

 

Good job

 

Sweet, glad to hear you got if figured out.