92 blazer s10 help please

i have a 92 blazer s10 with the 4.3 vortec engine, its been over heating bad, the temp gauge jumps up, but when i drove slow and steady it went down till i accelereated more, now it heats up after a couple miles in town. im getting ready to try and change the thermostat but heard it could be as easy as the radiator cap? can anyone help me please? thanks

Change the thermostat.
If you hear a gurgling sound behind the glovebox or the radiator hoses don't get tight with pressure, change the radiator cap.

i changed the thermostat, still overheats. i will change the rad. cap today .

cant believe it, i bought a stant rad. cap like suggested put it on and sure s#$t it works, thanks for the help.

factory caps are notorious for being defective so good move.

Make sure you top up the cooling system and fill the overflow tank up to just below the overflow tube.

Then allow it to burp the excess out and settle and you will have the perfect level.

yup got it covered am noticing a small leak somewhere, antifreeze collecting at the bottom the the radiator by fan shrowd, could be from when i flushed the lines though. its running great hasnt even come close to overheating, one thing when i flushed the lines i noticed this grey mirky color with the antifreeze i thought maybe someone put it some stop leak before i dont know. but its running.

does anyone know what the grey mirky stuff could be? or what to do, will it effect stuff badly, not to worry ? anything? please let me know. thanks

Could be the coolant being too old and breaking down.

Maybe flush it again at the end of the winter just to be safe.

kick down cable loose, went to push in that silver button to adjust it, felt the cable still loose slides in and out, what wrong ? any ideas