Ah yes, dielectric grease...thanks. I am using the stock ECU but programmed out VATS, EGR and a few other changes. Of course I don't have factory gauges but a sensor for the ECU and one for the gauge. Dash gauge and laser thermometer seem to read the same.

 

This guy is smart!

 

do you have a scanner that can see what's going on when running? if its doing it when going from open to closed loop that would make it seem like a temp issue but could be sensor issue.

 

I just ran down for some gas and it did it again. Got home and put the fuel pressure gauge on it and it read steady 39 Lbs while engine was stumbling. Discovered check engine light was on (located in the trunk). Checked the code...err15...which is low coolant temp. Didn't have time to see if it was going into closed loop. When I get time I'll check the ref voltage and ground to ensure wiring is OK. New sensor but that doesn't mean it won't go bad. More info when I scan to see if it's going into closed loop and make sure there is no air bubbles. Everything was fine until several days ago when it started acting up so I'm narrowing it down.

 

test your temp sensors with ohm meter. look at 20 here 4th Gen LT1 F-Body Tech Aids

 

I put EEHACK on it and the coolant temp is stuck at the north pole (- 40) and does not move even when I go into closed loop. Picked up a new sensor on the way home from golf this morning (shot a 78). Will post results when I change it out.

 

Kept dragging my feet about putting the new sensor in because it's very close to the radiator fan and I'll have coolant spill. Finally went out and changed the sensor...took 5 minutes and just a bit of coolant to soak up. Everything is working normal now. According to EEHACK the sensor is reading as it should. The sensor I took out was new. didn't last 200 miles.

 

go through bleeding air from coolant system to make sure there is no air in it.

 

Good news about bleeding is that my radiator top tank is above the engine.

 

because the lt1 is reverse flow there are what I call dead zones where air can be trapped. that's why there are bleeder screws where they are and there is a pipe going from one head to the other at the rear. even with that the heads have a spot at the rear where air can be trapped and cause a hot spot that can also cause a boil over. I have found that if you get the front of the engine up high while bleeding or let set overnight then bleed has helped to get that bubble out.