hi all i got a 1990 bird with an 88 GTA 5.7 tpi motor. i just swapped in a new radiator a HOWE dual core radiator. i made a custom radiator support bracket anyway... i also wired my fans to come on with a switch inside the car that i can turn off and on. i drove my car last night MAYBE 2 miles and my temp on the gauge was at 260..... and still going up. anyway got home and herd my car making a bubbling noise so i poped my hood and noticed my overflow bottle was ready to like explode... i let it sit for about 5 mins so i could TOUCH the overflow cap FORGET THE RADIATOR CAP lol. it was bubbling and it was HOT. not too sure what it could be. as a side note i have read some other posts and alot of people turn to the hoses. well the bottom hose i replaced with a custom hose that it basically a long spring wrapped in rubber so it isnt crushing in. the top one dosnt crush either and gets VERY HOT after the thermostat opens. i only have 3 hoses going to the radiator one for the top, one for the bottom, and one for the overflow. i dont have a heater so i capped that off at the manifold. and i installed an aftermarket radiator cooler. the motor now probably has about 10 miles on it i rebuilt it myself. just very very confussed on what it can be. my frined thinks its timming but i dont know. i set the base timing at like 9 and when i plugged back in the cable the timming was at like over 25 or so. i have an LT4 hot cam and 1.6 roller rockers. please some one help me out. also having wireing issues and tranny issues but thats for another post i guess....

 

When did you turn the fans on?
Do you have the air dam on the bottom of the car?
Could be a sticky t-stat.
Biggest thing is to make sure the radiator is getting air.