Black Betty just stared running really hot. Would hang out around 250- 260, and now it pegs at 280 after changing the thermostat yesturday. All the limp mode stuff comes on, tells me a/c is turned off, then to idle the engine then to turn it off and it reduces power. I cant find the "weep" hole in the water pump. Could i have a massive air pocket in the system? bad water pump, or sending unit?

if you have a ir temp gun you can run the car and shoot the neck where the thermo is and see if the gauge is accurate. if it is sounds like water pump

Its possible you have an airpocket, or a thermostat that is stuck closed. Did you test its operation prior to installing it?

sounds like intake gaskets to me. u need to pressure test the system first. letting the temp get so high, u are going to be doing head gaskets if u keep that up...

sorry, just re-read your post. now that i know it'* a northstar and not a 3800...? good luck...

If i remember right the northstar has the water pump running of the cam belt on rear of the motor(tranny side). There kinda of a pain to change.

Ok, just checked the housing with the IR thermometer...one side 198.6, other side 161, with the gauge pegged at 280. After breaking open the cooling system to replace the thermostat do i need to extract the air out? Im still thinking its a bad sending unit too. Have to hunt that down, LOL

if you measure less than 200 there its running at the normal temp and you have a gauge or sender problem

I'm leaning towards a sender. If it were a gauge problem the limp mode wouldn't activate. Just my thinking though...makes sence to me, LOL

I agree