I have a 1994 firebird with an lt1. The engine had bad main bearings so i pulled it and rebuilt it. New crank and bearings new pistons and rings and all new gaskets. Everything was torqued to spec. The car ran fine the first time out. Now it overheats and i cant get it to stop. I did the combustion gas test and it didnt show any gasses showing up in the cooling system. Thought it was a bad thermostate, that is new, so i pulled it out and still overheated. No heat coming from the heater at all either. I have bled and bled and bled the system. Im at a loss. It doesnt look like the coolant is circulating through the engine its just pumping itout. I dont know what to do. No coolant in the oil or oil in the coolant and no steam comming from the exahust. Anyone have any ideas??

 

These reverse cooling systems are notoriously difficult to bleed. www.shbox.com has the bleeding instructions for proper bleeding. Have you checked the water pump?

 

I always had good luck pulling the thermostat housing and filling the system there. Cap that off and then fill the rest of the way at the radiator. Never had to touch it again and it vertually bled itself.

 

The waterpump is new and was working fine on the first drive. It did heat up at stoplights though. I will try bleeding the system more.

 

When I was rebuilding mine it kept over heating, the problem wound up being the hoses on the heater core were put on wrong and needed to be switched

Edit: or a heater hose could be going to the wrong place

 

This was my method as well, but I used my E waterpump to bleed the system while everything was off.

 

Ok. I removed the thermostat housing off than thermostat out and fired the car. None of the coolant moved. Water pump bad??

 

Prolly a bad waterpump, also I wouldn't call that the greatest idea lol. You'll need to remove it to tell whether it works or not.

 

Maybe you forgot the waterpump coupling?

 

Lol yes probably not a good idea to do but ran out of options on what was going on. Thought if i pulled that off and i could see the coolant circulate or run over then i could rule the pump out. I have been fighting this for a week now.