i have put two new thrmostats in my 86 iroc. each of them are 195 degree thermostats. each one would allow the car to get to 200 degrees and then open up. the engine temp would drop to 160 degrees and remain there. two different thermos from two different parts stores. any idea on what i should look for? of course, 305, 700r4. could a faulty temp sending unit do this? that is the only thing in common to them both. gauge proves it will read.

Does your car still have the heater control valve? If not, then coolant is allowed to bypass the thermostat via the heater core. I have mine set up this way, but in Texas it doesn't really get cold enough to worry about.

still has the heater control and it works also.

i am going to change the temp sending unit anyway. cant hurt. i shot the base of the thermostat housing with an infered heat gun and got 180 degrees idling. i know i have temp at the housing. with the tsu being in the head, i wonder about the differential in the temp reading at the two locations. i like the idea of welding a bung in the thermo housing and moving the tsu to that location. any thoughts about that?

They sell tstat housings with that bung already in it I got mine off ebay for $14 shipped.

thanks

it was the sending unit. one down, many to go!